Аннотация (русский):
The purpose of the monograph, which contains a modern view of the problem of adaptation of children with extremely low body weight, is to provide a wide range of doctors with basic information about the clinical picture, functional activity of innate and adaptive immunity, prognostic criteria of postnatal pathology, based on their own research. The specific features of the immunological reactivity of premature infants of various gestational ages who have developed bronchopulmonary dysplasia (BPD) and retinopathy of newborns (RN) from the moment of birth and after reaching postconceptional age (37-40 weeks) are described separately. The mechanisms of their implementation with the participation of factors of innate and adaptive immunity are considered in detail. Methods for early prediction of BPD and RN with the determination of an integral indicator and an algorithm for the management of premature infants with a high risk of postnatal complications at the stage of early rehabilitation are proposed. The information provided makes it possible to personify the treatment, preventive and rehabilitation measures in premature babies. The monograph is intended for obstetricians-gynecologists, neonatologists, pediatricians, allergists-immunologists, doctors of other specialties, residents, students of the system of continuing medical education. This work was done with financial support from the Ministry of Education and Science, grant of the President of the Russian Federation No. MK-1140.2020.7.

Ключевые слова:
Children, extremely low body mass, neonatal pathology, immune system, weight, immunity, postnatal pathology, newborns

3.1. Formation of adaptive and innate immunity in children with extremely low body weight in the dynamics of the postnatal period The immune system is one of the most unique body systems with the ability to respond quickly to various pathogens and regulate the functions of homeostasis systems during pathological processes, which determines the survival of a premature infant, the features of the postnatal period of life, the effectiveness of therapeutic and rehabilitation measures. At the moment, the individual links of the immune system in premature newborns with various pathological conditions have been described in detail. At the same time, there are very few sources containing information on the relationship between innate and adaptive immunity in children with ELBW in the dynamics of the postnatal period, which does not allow adequately assessing the coherence of immune processes and forming an idea of various mechanisms of immunological response in very premature infants. The maturity of the morphological substrate of the immune system of very premature infants with ELBW at the time of birth depends on the child's hepatitis B, antigen load, pathological influences, which the fetus is exposed to in the antenatal period during complicated pregnancy, as well as the violation of the relationship of immunity in the mother - fetus - newborn system [1 , 2]. According to the literature, in very premature infants, the rate of maturation of the immune system differs from that in full-term infants. In contrast to full-term newborns, in children with gestational age less than 32 weeks, immunocompetent cells are immature, similar to fetal cells. Therefore, during the period of massive antigen load after birth, they are not able to provide efficiently adequate protection for the child [3]. This state of immunity in premature infants prevents the formation of overreaction processes at a high antigen load in the intra- and neonatal periods, and the mechanisms of the innate immunity link prevent the development of infection at the earliest stages as a result of the elimination of pathogens. Adaptive immunity is realized by lymphocytes, and it can also be divided into two components (links): humoral and cellular. The basis for the development of infectious and inflammatory pathology is the immaturity of the innate and adaptive links of immunity both at the systemic and local levels [4, 5, 6]. Humoral immunity is realized by B-lymphocytes and immunoglobulins produced by them. When meeting an antigen and recognizing it, B-lymphocytes are transformed into plasma cells that synthesize antibodies. Antibodies provide protection against bacteria, bacterial toxins, viruses that circulate freely in body fluids before entering cells. The cellular link of the adaptive immunity of deeply premature newborns is characterized by an increased number of "naive" T-lymphocytes [7], which, in comparison with mature T-cells, when interacting with antigens, produce a smaller amount of gamma-interferon and other cytokines. In addition, the interaction of T and B lymphocytes is difficult in the course of the immune response and there is a reduced number of cells of immunological memory [4, 8]. According to E. L. Semikina (2008), an analysis of the expression of the main antigens of T-linear differentiation in very premature infants indicates a sufficient maturity of this system by the time of birth. The researchers noted an increase in the level of cells with the phenotype CD3 +, CD4 +, CD8 + and the prevalence of cells with a low specificity of their antigen-recognizing immunoglobulin receptors in the total pool of B-lymphocytes [9]. Evaluation of the cellular component of immunity in very premature infants with ELBW at birth showed a decrease in the relative number of T cells, CD4 + lymphocytes, the ratio of CD4 / CD8 populations, and an increase in the number of natural killer cells (NK) in umbilical cord blood [10]. A number of studies have shown that by the end of the neonatal period in children with ELBW, compared with full-term newborns, leukocytopenia and relative lymphocytosis persist. The decrease in the relative content of CD3 + and CD4 + - lymphocytes and the value of the immunoregulatory index is due to the suppressive direction of cellular reactions. The reduced amount of serum immunoglobulins is compensated by the increased content of B-lymphocytes. An increase in the number of NK cells characterizes a high cytotoxic potential and, in conditions of a decrease in the number of neutrophils, is one of the only factors of antigen-independent cell defense [7, 11]. The CD95 receptor transmits a cytotoxic signal when it binds to specific antibodies. The CD95 receptor plays an important role in the physiology of apoptosis: the peripheral removal of activated mature T cells in the final stages of the immune response. The receptor for IL-2, CD25, is produced by T cells in response to antigenic and mitogenic stimulation. The cytokine IL-2 is required for the proliferation of the T-cell link and other processes that regulate the immune response. The CD71 receptor appears on leukocytes upon activation. It is found on most dividing cells. As a transferrin receptor, CD71 allows the entry of iron ions into the activated cell, which is necessary for cell division. There is evidence that CD71 + cells can have an anti-inflammatory effect in the postnatal period of a newborn's life [12]. These markers of leukocyte subpopulations serve as indicators of the competence of the cellular link of the newborn's immune system. The key point is the formation of the antigen-presenting function, when different populations of cells interact to protect the body from the action of the antigen. When analyzing the immunological parameters of umbilical cord blood in all very premature infants with ELBW, a significant decrease in the number of leukocytes was recorded (p1-3 = 0.06, p2-3 = 0.007) in combination with an increase in the percentage of lymphocytes (p1-3.2-3 = 0 , 0001) compared to term infants. The most pronounced changes were observed in children born at the time of very early preterm labor, which is associated with the peculiarity of early ontogenesis and defective leukopoiesis against the background of the pathological course of the antenatal period (Table 15). Table 15 Population and subpopulation composition of umbilical cord blood lymphocytes in children with ELBW Indicators 1st group (n=46) 2nd group (n=43) 3rd group (n=25) р Me (25-75) Me (25-75) Me (25-75) Leukocytes, 109/l 6,15 (4,42-10,71) 6,28 (4,7-10,62) 10,85 (9-14,5) р1-3=0,017 р2-3=0,007 Leukocytes, % 71 (57,25-75,75) 70,5 (60,5-77,5) 34 (29-41) р1-3=0,0001 р2-3=0,0001 Leukocytes, 109/l 3,94 (3,36-5,93) 4,01 (3,29-7,51) 4,25 (3,16-5,07) CD3+, % 43,5 (34,75-51) 46,5 (39,25-52,75) 50 (39-57) CD3+, 109/l 1,85 (1,3-2,57) 1,88 (1,33-3,16) 1,99 (1,39-2,57) CD19, % 12 (6,75-17,5) 14 (9,25-17) 15 (12,0-18,0) р1-2=0,045 CD19, 109/l 0,56 (0,24-1,16) 0,59 (0,42-0,8) 0,63 (0,36-0,97) CD4+, % 28,5 (23,75-38,25) 32,5 (25,25-39,25) 37 (29-43) CD4+, 109/l 1,07 (0,79-2) 1,25 (0,94-2,42) 1,47 (1,04-2,06) CD8+, % 11 (8,75-14,25) 13 (10,25-17) 15,5 (12-19) CD8+, 109/l 0,46 (0,26-0,69) 0,59 (0,45-0,85) 0,58 (0,43-0,61) CD4/CD8 2,8 (2,1-3,66) 2,32 (1,71-3,25) 2,39 (1,78-2,96) CD25+CD4+, % 3 (2-5) 4 (2-4,75) 3 (2-4) CD25+CD4+, 109/l 0,12 (0,08-0,26) 0,17 (0,12-0,34) 0,11 (0,09-0,18) р2-3=0,012 Note. р1-2, р1-3, р2-3 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. The results of phenotyping of leukocytes by flow cytofluorometry showed that mature T-lymphocytes with the CD3 phenotype accounted for more than 40% of cord blood lymphocytes in very premature infants of all examined groups. When comparing the indicators of the main subpopulations of T- and B-lymphocytes of the umbilical cord blood of the main groups, no significant differences were found. One of the important results of activation is the expression of genes for growth factors and their receptors. Thus, an increase in the absolute number of regulatory cells with a receptor for IL-2, which is an activation marker (CD25 + CD4 +) (p2-3 = 0.012), was observed in newborns with ELBW 28-31 weeks of GA, which contributes to the implementation of accelerated differentiation of regulatory lymphocyte populations [13 ]. In children born at the time of very early preterm birth, the expression of the CD25 + / CD4 + receptor did not differ from that of full-term infants. To characterize the balance of cytokine-producing lymphocytes of the first and second order, the ratio of the percentage of Th1- / Th2- lymphocytes (CD4 + IFN +, CD4 + IL-4 +) was determined, which was calculated for each representative of the age group in spontaneous and induced tests. When analyzing the indices of intracellular cytokines of the umbilical cord blood in all premature infants, a decrease in the content of T-helpers spontaneously synthesizing IL-4 was noted (Table 16). At the same time, the level of IFN-γ expression did not differ from that of the comparison group. The ratio of regulatory subpopulations producing Th1 and Th2 cytokines in all premature infants in the spontaneous test had a pro-inflammatory orientation and was 1.7 and 1.9 times higher than the indices of full-term infants (p1-3.2-3 = 0.001). Upon cell stimulation, the polarization index significantly increased in premature infants with a shorter gestation period (p1-3 = 0.001). Table 16 The content of cytokine-producing cells in the umbilical cord blood of children with ELBW Indicators 1 group (n=46) 2 group (n=43) 3rd group (n=25) р Me(25-75) Me(25-75) Me (25-75) CD4+CD3+IFN-γ+ self-existing, % 2,89(1,74-4,0) 2,36(1,66-6,09) 2,36(1,66-6,09) CD4+IFN-γ+ suscitate, % 4,49(2,69-6,34) 4,58(1,64-7,67) 3,27(1,17-6,83) CD4+IL-4+ self-existing, % 2,1(0,91-3,02) 1,65(0,83-3,17) 3,45(2,71-4,97) р1-3, 2-3=0,001 CD4+IL-4+ suscitate, % 4,59(2,73-5,42) 3,8(2,97-5,13) 4,48(3,89-6,53) р1-3, 2-3 =0,04 CD4+IFN-γ+ / CD4+IL-4+ self-existing, c.u. 1,35(1,26-1,75) 1,56(1,41-2,0) 0,79(0,71-0,97) р1-3, 2-3=0,0001 CD4+IFN-γ+ / CD4+IL-4+ suscitate, c.u. 1,2(1,03-1,52) 1,19(0,65-1,3) 1,05(0,61-1,39) р1-3=0,001 Note. р1-2, р1-3, р2-3 - significance of differences between groups of children: 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. The hypoxic effect on the fetus in the antenatal period affects the change in immunological parameters, directly reflects the negative effect of placental insufficiency on the development of the immune response of children with ELBW. In children with GA of22-27 weeks, positive correlations were found between the development of subcompensated CPI in the mother and the content of cytokine-producing cells (CD4+ IL-4+ and CD4+ IFN-γ +, r = 0.87 at p = 0.010 in both cases ), the presence of preeclampsia of moderate severity and the index of polarization of cytokine-producing cells upon stimulation (r = 0.87 at p = 0.010). We found a correlation between the presence of children of the 1st group on ALV from birth and the level of regulatory cells (CD25 + CD4+) (r = 0.57, p = 0.001) as well as the induced production of intracellular IL-4 (r = 0.50, p = 0.01) reflects the effect of oxygen deficiency on the formation of cytokine balance and the reserve of cytokine-producing cells. By the end of the late neonatal period, a decrease in the number of leukocytes and relative lymphocytosis in the peripheral blood of all premature infants remained (Table 17). Table 17 The main subpopulations of peripheral blood lymphocytes in children with ELBW at the age of 1 month of life Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me(25-75) Me(25-75) Me (25-75) Leukocytes,109/l 6,9 (5,88-8,93) 7,38 (5,84-8,86) 10,85 (9-14,5) р1-3=0,0001 р2-3=0,0001 Lymphocytes, % 60 (47,5-65) 60 (51,5-74,25) 34 (29-41) р1-2≥0,05 р1-3=0,0001 р2-3=0,0001 Lymphocytes, 109/l 4,28 (3,31-5,71) 4,35 (3,39-5,64) 4,25 (3,16-5,07) CD3+, % 54 (48-67) 55 (44-64) 50 (39-57) CD3+, 109/l 2,32 (1,56-2,85) 2,44 (1,89-3,2) 2,01 (1,56-2,66) CD19+, % 10,5 (8,0-16,75) 15 (9,0-20,0) 15 (12,0-18,0) CD19+, 109/l 0,49 (0,18-0,73) 0,51 (0,38-0,98) 0,63 (0,36-0,97) CD4+, % 40 (28,5-47) 40 (30,5-46) 37 (29-43) CD4+, 109/l 1,78 (1,18-1,95) 1,62 (1,29-2,06) 1,47 (1,04-2,06) CD8+, % 18 (14-24) 15,5 (12-19) 15,5 (12-19) CD8+, 109/l 0,68 (0,55-1,02) 0,58 (0,43-0,61) 0,58 (0,43-0,61) CD4/CD8 2,27 (1,1-2,93) 2,25 (1,89-2,89) 2,39 (1,78-2,96) CD25+CD4+, % 6 (4-7) 5,5 (4-6) 3 (2-4) р1-3=0,0001 р2-3=0,0001 CD25+CD4+, 109/l 0,2 (0,17-0,3) 0,26 (0,18-0,31) 0,11 (0,09-0,18) р1-3=0,015 р2-3=0,0001 Note: р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. The number of T- and B-lymphocytes and their subpopulations did not differ from those of full-term newborns. During this period, all premature infants showed an increase in the relative and absolute number of regulatory cells with a receptor for IL-2, which is an activation marker (CD25+ CD4+) (p1-3.2-3 <0.015), which contributes to the accelerated differentiation of regulatory lymphocyte populations. By the age of 1 month of life, all premature infants had a reduced number of T-helpers producing IL-4, as a result of which the first order lymphocytes predominated in the pool, which is associated with antigenic stimulation with bacterial agents (Table 18). Table 18 The content of cytokine-producing cells in children with ELBW at the age of 1 month of life Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me(25-75) Me(25-75) Me (25-75) CD4+IFN-γ+ self-existing, % 2,02 (1,23-4,22) 2,52 (1,42-4,05) 2,36(1,66-6,09) CD4+IFN-γ+ suscitate, % 4,04(12,58-6,16) 5,35(3,57-6,66) 3,27(1,17-6,83) CD4+IL-4+ self-existing, % 1,77 (0,91-3,1) 1,45 (1,03-2,49) 3,45(2,71-4,97) Р1-3, 2-3=0,0001 CD4+IL-4+ suscitate, % 2,71 (1,7-3,44) 3,9 (2,8-4,73) 4,48(3,89-6,53) Р1-3=0,001 Р2-3=0,016 CD4+IFN-γ+ / CD4+IL-4+ self-existing, c.u. 1,35 (1,22-1,55) 1,77 (1,37-2,09) 0,79(0,71-0,97) Р1-3, 2-3=0,0001 CD4+IFN-γ+ / CD4+IL-4+ suscitate, c.u. 1,73(1,55-2,47) 1,31(1,17-1,66) 1,05(0,61-1,39) Р1-3=0,01 Р2-3=0,016 Note: p1-2 - the significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. Upon stimulation of cytokine-producing cells, the revealed changes persisted. Upon reaching the post-conceptional age of 38-40 weeks in premature infants, the level of leukocytes remained reduced (p1-3.2-3 = 0.0001), the relative number of lymphocytes - increased (p1-3.2-3 = 0.0001), compared with full-term newborns, which indicates a high risk of an infectious process in children with ELBW (Table 19). Table 19 The main subpopulations of peripheral blood lymphocytes in children with ELBW at 38-40 weeks of PCA Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me (25-75) Me (25-75) Me (25-75) Leukocytes, 109/ l 6,3 (5,32-6,8) 6,75 (5,8-8,55) 10,85 (9-14,5) р1-3=0,0001 р2-3=0,0001 Lymphocytes, % 68 (64-78,5) 68 (60-72) 34 (29-41) р1-3=0,0001 р2-3=0,0001 Lymphocytes, 109/l 4,35 (3,62-4,97) 4,62 (4,06-5,14) 4,25 (3,16-5,07) CD3+, % 51,5 (41,5-58,25) 50 (44-53) 50 (39-57) CD3+, 109/l 2,04 (1,66-2,69) 2,22 (2-2,57) 1,99 (1,39-2,57) CD19+, % 29 (17,25-33,75) 28 (21-31) 12 (8-15) р1-3=0,0001 р2-3=0,0001 CD19+, 109/l 1,22 (0,59-1,51) 1,22 (0,96-1,8) 0,36 (0,29-0,74) р1-3=0,002 р2-3=0,0001 CD4+, % 31,5 (24-37,5) 33 (28-37) 37 (29-43) CD4+, 109/l 1,35 (1-1,73) 1,52 (1,26-1,83) 1,47 (1,04-2,06) CD8+, % 16,5 (13-23,5) 15 (12-19) 15,5 (12-19) CD8+, 109/l 0,65 (0,5-0,78) 0,65 (0,58-0,87) 0,58 (0,43-0,61) CD4/CD8 2,17 (1,42-2,56) 2,17 (1,63-3,08) 2,39 (1,78-2,96) CD25+CD4+, % 4 (3,5-5) 5 (4-5) 3 (2-4) р2-3=0,02 р1-3=0,0001 CD25+CD4+, 109/l 0,17 (0,15-0,24) 0,22 (0,2-0,26) 0,11(0,09-0,18) р1-2=0,036 р1-3=0,0001 Note. р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. The relative number of subpopulations of T-lymphocytes in children of the main groups upon reaching PCA 38-40 weeks was comparable to the indicators of the comparison group. The activation of the B-cell link of immunity was indicated by a significant increase in the number of B-lymphocytes in very premature infants with ELBW (p1-3.2-3 = 0.001). In premature infants with ELBW, an increase in both the relative and absolute number of regulatory cells with the CD25+/CD4+ receptor remained (p2-3 = 0.012). The analysis of intracellular cytokines showed that upon reaching the age of a full-term child, a significantly reduced number of CD4+ IL-4+ cells in the spontaneous test remained in all children (Table 20). Table 20 The content of cytokine-producing cells in children with ELBW at 38-40 weeks of PCA Indicators 1 group (n=42) 2 group (n=43) 3rd group (n=25) р Me(25-75) Me(25-75) Me (25-75) CD4+IFN-γ+ self-existing, % 3,08 (1,93-4,07) 2,85 (2,26-4,77) 2,36(1,66-6,09) CD4+IFN-γ+ suscitate, % 6,3 (3,44-8,87) 3,88 (2,82-5,95) 3,27(1,17-6,83) CD4+IL-4+ self-existing, % 1,32 (1,25-3,2) 1,44 (1,08-2,3) 3,45(2,71-4,97) Р1-3, 2-3=0,0001 CD4+IL-4+ suscitate, % 3,21 (2,06-5,56) 3,88 2,82-5,95) 4,48(3,89-6,53) CD4+IFN-γ+ / CD3+IL-4+ self-existing, c.u. 1,41 (1,27-1,77) 1,78 (1,57-1,97) 0,79(0,71-0,97) р1-3, 2-3=0,0001 р1-2=0,018 CD4++IFN-γ+ / CD4+IL-4+ suscitate, c.u. 1,96 (1,26-2,55) 1,05 (0,98-2,42) 1,05(0,61-1,39) р1-3, 2-3=0,017 Note. р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. When stimulating cytokine-producing cells, there were no significant differences with the indicators of umbilical cord blood in full-term infants. The ratio of the number of IFN- γ and IL-4 producing lymphocytes in all newborns with ELBW remained higher compared to those in full-term infants. The children of the 2nd group showed the maximum values of the cell polarization index in the spontaneous test. Thus, the studies carried out made it possible to identify some regularities in the formation mechanism of innate and adaptive immunity. In all children with ELBW, regardless of gestational age, against the background of a decrease in the number of leukocytes, an increase in the relative number of lymphocytes was found, which reflects the physiological process of "learning" of many clones of T and B cells carrying TCR receptors for recognizing foreign antigens. The absence of significant differences in the number of CD3-, CD19-, CD4- and CD8 - populations, indicates the achievement of the required number of mature cells in the development of the cellular link of immunity in the main populations of lymphocytes by 22 weeks of gestational age. The development of the immune response towards a Th1-dependent cellular or Th2-humoral response directly depends on the induction of the cytokine signal received by the cells. When studying the production of intracellular cytokines in premature infants, a decrease in the number of cytokine-producing CD4+ IFN-γ+ cells was found regardless of the presence or absence of lymphocyte stimulation. That resulted in an increase in the polarization index (CD4+ IFN-γ+/CD4+ IL-4+) cells and the inflammatory direction of the immune response. An increase in the polarization index (IFN-γ/IL-4) more than 1.0 was recorded in children with ELBW in 95.7% and 97% of cases, respectively. In full-term infants, the shift in the balance of cytokine-producing cells towards the Th2-dependent immune response was dominant in 72.3% of cases, respectively (p <0.017). The revealed changes persisted throughout the entire period of nursing premature babies. Nevertheless, at the age of 1 month in children with ELBW, the number of regulatory cells expressing the IL-2R (CD25+) receptor increases, and upon reaching PCA 38-40 weeks, the proportion of B-lymphocytes increases in comparison with the indicators of term infants, which indicates "maturity" of cellular responses of adaptive immunity. It should be noted a statistically significant decrease in the number of cells producing IL-4 in children born at the time of very early preterm labor, which indicates inhibition of early cell activation processes and indicates a shift in the balance of immunocompetent cells in favor of systemic suppression. 3.2. Study of innate immunity indices in children with extremely low body weight in the dynamics of the postnatal period The prospects for the full rehabilitation of deeply premature children are largely determined by immunological mechanisms [1]. It has been proven that the child's immune system plays a leading role in the pathogenesis, clinical course and outcome of hypoxic and infectious diseases. Immaturity of the immune system due to the violation of the evolutionarily determined course of postnatal adaptation under conditions of increased antigenic load in the perinatal period prevents the development of an overreaction. The mechanisms of innate immunity prevent the development of the infectious process at the earliest stages as a result of the rapid elimination of pathogens, when the mechanisms of adaptive immunity are not yet function [2]. The factors of innate immunity include cells of the monocytic-macrophage link, neutrophils, the complement system, natural killer cells and cytokines produced by these cells, the factors of adaptive immunity - T- and B-lymphocytes and their subpopulations, immunoglobulins of various classes. Monocytes and macrophages, derived from a common myeloid precursor, play an important role in the immune system [3]. In response to differentiation factors, some monocytes migrate and fill the tissues of the body, thereby avoiding apoptosis. Monocytes and their precursors can activate or inhibit the immune response, depending on local and systemic signals [4]. The key role in ensuring the reactions of innate immunity belongs to the cytokine system, which carries out intercellular interaction between innate and adaptive links of immunobiological control [5, 6]. Disruption of the balance of pro- and anti-inflammatory cytokines necessary for the formation of adequate adaptive immunity, systemic mechanisms of the body's natural resistance can lead to significant local activation of the inflammatory process and even its generalization, followed by rapid depletion [2, 6, 7], which subsequently leads to the development of multiple organ failure. In some cases, the determination of cytokines allows them to be used as criteria for the diagnosis and prediction of morbidity and mortality in newborns, differentiating infectious and non-infectious pathologies, improving the differential diagnosis of various inflammatory diseases [8, 9, 10, 11, 12]. Thus, most researchers conclude that, along with the level of procalcitonin and C-reactive protein (CRP), the indicators of IL-6, -8, tumor necrosis factor-α (TNF-α) are the earliest and most specific markers of sepsis in newborns [13 , 14, 15]. High levels of IL-6 in umbilical cord blood are associated with an increased risk of morbidity and mortality in the newborn [9, 16]. According to T.G. Kredient there is a relationship between increased levels of IL-6 and IL-8 with RDS-associated inflammation and early peri / intraventricular hemorrhages [17]. The data of foreign authors indicate a significant dependence of high levels of proinflammatory cytokines in the blood serum of premature infants who developed PVL [18, 19]. Excessive production of IL-4, IL-8, TNF-α in hypoxic conditions of the brain in newborns can lead to secondary periventricular necrosis and are associated with an unfavorable course of the disease [20, 21]. In recent years, data have appeared proving the polymorphism of genes encoding the excessive production of proinflammatory cytokines IL-6, IL-8, TNF-α and, thereby, a genetic predisposition to PVL and cerebral palsy [10]. From the point of view of genetics, the development of BPD is determined by a complex interaction of various genes and environmental factors [22]. Regardless of the multifactorial etiology, the pathogenesis of BPD is based on inflammation, which subsequently progresses. Cytokines, modulating the immune defense, are involved in the normal development of lung tissue and, during the development of BPD, mediate acute lung injury, aggravating ventilation-associated lung damage [23]. In a study by N. Ambalavanan et al. (2009) it was found that children with ELBW at birth had high serum concentrations of some cytokines (interleukin (IL) 1β, IL-6, IL-8, IL-10, interferon-γ (IFN-γ)) and low concentrations other cytokines (IL-17; chemokine expressed and secreted by T cells upon activation (RANTES). Tumor necrosis factor-β) have been associated with the development of BPD and death [24]. It was found in the work of A. K. Maksutova that the level of IL-4 production in children with congenital generalized infections does not depend on the gestational age of newborns, while the level of pro-inflammatory cytokines (IFN-γ, TNF-α) is higher in full-term children. [25]. As an anti-infectious defense, the importance of the interferon system, which is of great importance in the formation of immunity, is increasing [26, 27]. In the study of V. A. Pertseva a tendency towards suppression of interferonogenesis was noted in children with ELBW, during the formation of infectious and inflammatory diseases [28]. The innate immune system plays an important role in the pathogenesis of infectious and inflammatory diseases. The formation of the child's immune response and resistance to increased microbial colonization is determined by the functioning of cellular factors of nonspecific resistance (micro- and macrophages). Cells of the myeloid series, including monocytes, are involved in the implementation of the effector mechanisms of the innate immunity of premature infants, including monocytes, on the ability of which to phagocytosis depends on the blocking of vital activity, disintegration and removal of the pathogen from the body. The phagocytosis process can be divided into several stages: object recognition, activation, chemotaxis, adhesion, phagocytosis, digestion, antigen presentation. The activation of positive CD64 neutrophils is considered an early sign of an immune response to a bacterial infection, which occurs approximately one hour after an infectious invasion. It was found that the expression of CD64 is increased in blood samples from newborns with sepsis [29]. Determination of CD64 demonstrates a greater degree of sensitivity than the method for determining C-reactive protein or IL-6, both in early and late forms of sepsis [30]. The CD11b marker mediates inflammation by regulating leukocyte adhesion and migration [31]. In the case of the development of an infectious process, the expression of CD11b increases on neutrophils and monocytes. It has been found that CD11b is a very effective marker in the diagnosis of early onset neonatal infection. Compared with uninfected newborns, the expression of the receptor in sepsis is increased [32, 33]. HLA-DR protein is a class II receptor of the MHC histocompatibility complex, which forms a ligand for the T-cell receptor of T-helper cells. According to Kanakoudi-Tsakalidou data, the HLA-DR expression on monocytes can be critical also in the presence of respiratory distress syndrome [34]. At the same time, a decrease in the HLA-DR expression on circulating monocytes was observed in newborns with sepsis [35]. An important factor contributing to the adequate preparation of monocytes for the uptake of various foreign particles is the CD11b expression receptor by cells involved in the formation of contacts of leukocytes with the vascular endothelium, regulation of the inflammatory response, provision of intracellular signal transmission, and activation of leukocytes [36, 37]. Examination of indices of innate immunity in all premature infants revealed a significant decrease in the relative number of CD14+CD11b+ monocytes, which indicates the predominance of immature cells in the population and reflects a reduced readiness of effector cells to participate in the processes of antigen presentation and intercellular interaction [74] (Table 21 ). Table 21 Activation markers of umbilical cord blood monocytes in premature infants with ELBW Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me (25-75) Me (25-75) Me (25-75) CD11b+CD14+, % 30,0(15,0-62,0) 37,0(27,75-49,75) 70(67,0-77,0) p1-3, 2-3=,0001 CD11b+CD14+, abs. 0,15(0,08-0,18) 0,19(0,14-0,20) 0,39(0,37-0,95) p1-3, 2-3=0,010 CD64+CD14+, % 17 (8,0-34,0) 40 (24,5-43,5) 58,0 (33,5-71,0) р1-3=0,017 CD64+CD14+, 109/l 0,05 (0,04-0,16) 0,15 (0,11-0,22) 0,46 (0,35-0,72) р2-3=0,021 р1-3=0,009 CD14+HLA-DR+, % 21 (10,5-29) 33 (22-58) 53 (38-63,5) р1-2=0,014 р1-3=0,0001 р2-3=0,057 CD14/HLA-DR, 109/l 0,09 (0,05-0,14) 0,13 (0,075-0,18) 0,5 (0,34-0,84) р1-3=0,001 р2-3=0,002 CD71+CD14+, % 17 (11,0-19,5) 16 (12,0-44,0) 18,0 (16,5-21,5) CD71+CD14+, 109/l 0,18 (0,12-0,24) 0,18 (0,14-0,29) 0,21 (0,18-0,25) Note. р1-2, р1-3, р2-3 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. In premature infants, there was a significant decrease in the absolute number of CD64+ CD14+ cells compared to full-term infants (p1-3 = 0.009, p2-3 = 0.021). A decrease in the percentage of activated monocytes was found in children of the 1st group. HLA-DR belongs to class II molecules of the major tissue histocompatibility complex, which are responsible for the presentation of antigen to T cells. When comparing the indices of innate immunity of newborns of the main groups, a significant decrease in the percentage of CD14 + HLA-DR + in children of gestational age of 22-27 weeks was revealed (p1-2 = 0.014, p1-3 = 0.0001, p2-3 = 0.057), which, according to a number of authors, it correlates with an increase in the risk of infectious pathology. Correlation analysis revealed a strong positive relationship between the development of sepsis and the level of CD14 + HLA-DR + in umbilical cord blood in children of the 1st group (r = 0.73, p = 0.004), as well as the formation of a severe form of BPD in children of the 2nd groups (r = 0.52, p = 0.018). It is known that sepsis actively affects the decrease in HLA-DR on monocytes and glucocorticoids [38]. However, both main groups of women received antenatal prophylaxis of RDS with dexazone in 100% of cases. The transferrin receptor (CD71+) is an early activation marker, and an increase in its expression level is observed on proliferating cells. The relative number of monocytes carrying the transferrin receptor CD71/CD14 in the main groups of children corresponded to the values of full-term infants. In addition to monocytes, cells of innate immunity include natural killer cells (NK) - large granular lymphocytes that have the ability to destroy the virus infected cells. Statistically significant differences in percentage (4 (2-9) and 6 (3-12)% in the 1st and 2nd groups, versus 5 (3-6.75)% in the 3rd group, Р1-2, 2-3≥0.05) and absolute (0.13 (0.08-0.61) and 0.24 (0.082-0.58) 109/l versus 0.18 (0.12-0.29) ) 109/l indices of NK cells in the umbilical cord blood of premature and full-term infants, not detected The study of pro- and anti-inflammatory cytokines in the serum of umbilical cord blood showed that all preterm infants are diagnosed with a significant increase in the level of pro-inflammatory cytokines: IFN-γ and IL-8, which are predictors of the infectious process (p1-3, 2-3 = 0.0001 in all cases) (Table 22). Table 22 Levels of cytokines and acute phase proteins of the umbilical cord blood of the examined children Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me (25-75) Me (25-75) Me (25-75) IFN- γ, pg/ml 12,14 (10,81-13,68) 10,33 (2,83-11,94) 1,57(0,87-2,8) р1-2, 1-3, 2-3=0,001 IL-6, pg/ml 101,5 (11,16-147,3) 8,74 (3,95-16,31) 6,79 (3,56-14,77) р1-3, 1-2=0,001 IL-8, pg/ml 88,54 (71,2-158,1) 25,9 (15,4-55,6) 12,02 (6,75-15,06) р1-3, 2-3=0,001 р1-2=0,01 IL-4, pg/ml 0,61(0,48-0,87) 0,77(0,55-0,98) 3,33 (2,87-3,47) р1-3, 2-3=0,0001 Note. р1-2, р1-3, р2-3 - the significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. In contrast, IL-4 level was significantly reduced in both main groups. The increased concentration of IL-6 was recorded only in newborns of gestational age of 22-27 weeks, exceeding the indicators of children of the 2nd and 3rd groups by almost 11 times. At the age of 1 month of life, the number of activated monocytes in premature infants significantly increased, reaching the values of the comparison group (Table 23). All premature infants had a significant increase in the percentage of CD14 + HLA-DR + cells (p1-3 = 0.01, p2-3 = 0.002) relative to the parameters of the cord blood and the values of the comparison group. At the same time, the level of CD16+CD56+ -cells in children of the main groups, as in absolute (0.44 (0.3-0.75) and 0.36 (0.27-0.61) 109/L versus 0.18 ( 0.12-0.29) 109/L p1-3 = 0.002, p2-3 = 0.018), and in relative values (11 (8-16.5) and 9 (7-14)% versus 5 (3 -6.75)%, p1-3, 2-3 = 0.001) significantly exceeded the children's indicators of the 3rd group, which may be associated with a reaction to antigenic stimulation with bacterial agents. Table 23 Activation markers of peripheral blood monocytes in children with ELBW at 1 month of life Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me(25-75) Me(25-75) Me(25-75) CD11b+CD14+ % 59,5(49,5-78,5) 67,0(62,0-80,5) 70(67,0-77,0) CD11b+CD14+, abs. 0,47(0,33-0,69) 0,49(0,36-0,61) 0,39(0,37-0,95) CD64+CD14+, % 20 (4,75-41) 21 (10-55,5) 58,0 (33,5-71,0) CD64+CD14+ 109/l 0,14 (0,04-0,3) 0,22 (0,06-0,37) 0,46 (0,35-0,72) HLA-DR+ CD14+, % 67 (54-77,5) 67 (59-70,5) 53 (38-63,5) р1-3=0,01 р2-3=0,002 HLA-DR+ CD14+, 109/l 0,45 (0,28-0,8) 0,46 (0,35-0,58) 0,5 (0,34-0,84) CD71+CD14+, % 14 (6,5-15) 13 (6-23,5) 18,0 (16,5-21,5) CD71+CD14+, 109/l 0,08 (0,05-0,11) 0,09 (0,04-0,16) 0,21 (0,18-0,25) Note: р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. By the age of 1 month of life, IL-4 production in all premature infants increased relative to the initial level. However, it remained significantly lower than in the comparison group (Table 24). Table 24 Peripheral blood cytokine levels in premature infants with ELBW at the age of 1 month of life Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me (25-75) Me (25-75) Me (25-75) IFN- γ, pg/ml 3,77 (0,55-7,03) 2,76 (0,55-5,55) 1,57(0,87-2,8) IL-6, pg/ml 5,63 (4,6-10,97) 5,82 (4,08-14,06) 6,79 (3,56-14,77) IL-8, pg/ml 27,9 (23,29-36,95) 19,35 (12,77-28,3) 12,02 (6,75-15,06) р1-3, 2-3=0,001 IL-4, pg/ml 1,6 (1,37-1,79) 1,91 (1,55-2,06) 3,33 (2,87-3,47) р1-3, 2-3=0,0001 Note. р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. The amount of IFN-γ and IL-6 in children of the main groups did not differ from the indicators of full-term newborns. The concentration of IL-8 decreased slightly, but remained stably high. The results of the study of markers of monocyte activation are presented in table 25. An increased number of monocytes expressing the CD14+ HLA-DR+ receptor and the CD11b+ CD14+ adhesion molecule were observed in the peripheral blood of premature infants upon reaching PCA 38-40 weeks. In children of the 2nd group there was an increase in the relative number of CD64+CD14+ -monocytes, compared with the same indicators of children of the 1st and 3rd groups. The increased content of CD14 / HLA-DR monocytes positively correlated with the presence of pneumonia in children with lower ELBW at the age of 1 month of life (r = 0.48, p = 0.03). Table 25 Markers of peripheral blood monocyte activation in children with ELBW at PCA 38-40 weeks Indicators 1 group (n=42) 2 group (n=43) 3rd group (n=25) р Me(25-75) Me(25-75) Me(25-75) CD11b+CD14+, % 77(73,0-78,75) 82(78-85) 69(60,5-80,5) р1-3=0,017 р2-3=0,001 р1-2=0,047 CD11b+CD14+, abs. 0,24(0,23-0,51) 0,54(0,47-0,58) 0,36(0,14-0,71) CD64+CD14+ % 25,5 (17,5-39,5) 73 (65-87) 58,0 (33,5-71,0) р1-2, 2-3=0,010 CD64+CD14+, 109/l 0,14 (0,13-0,35) 0,5 (0,43-0,6) 0,46 (0,35-0,72) CD14+HLA-DR+, % 74 (64-82) 75 (63-80) 53 (38-63,5) р1-3=0,0001 р2-3=0,0001 CD14+HLA-DR+, 109/l 0,35 (0,28-0,55) 0,52 (0,42-0,66) 0,5 (0,34-0,84) р1-2=0,09 CD71+CD14+, % 14 (10-22,5) 16 (10-20) 18,0 (16,5-21,5) Note. р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. The increased relative number of NK cells in 1 month of life remained at a significantly high level in PCA 38-40 weeks (13 (7.25-20.5) and 13 (9-17)% versus 5 (3-6.75) %, р1-3, 2-3 = 0.001; 0.52 (0.3-0.76) and 0.64 (0.31-0.78) 109/l versus 0.18 (0.12-0 , 29) 109l, p1-3, 2-3 = 0.001). Upon reaching the post-conceptional age (37-40 weeks), all premature infants retained a reduced level of IL-4 (Table 26). Table 26 Levels of cytokines and acute phase proteins of peripheral blood of the examined children in PCA 38-40 weeks Indicators 1st group (n=42) 2nd group (n=43) 3rd group (n=25) р Me (25-75) Me (25-75) Me (25-75) IFN- γ, pg/ml 0,83 (0-3,6) 2,74 (0-5,69) 1,57(0,87-2,8) IL-6, pg/ml 3,78 (2,6-4,58) 5,1 (2,97-12,4) 6,79 (3,56-14,77) р1-3,=0,001 IL-8, pg/ml 14,71 (10,56-26,8) 12,82 (11,9-29,02) 12,02 (6,75-15,06) IL-4, pg/ml 2,05 (1,75-2,70) 2,22 (1,96-2,46) 3,33 (2,87-3,47) р1-3, 2-3=0,001 Note. р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation, 3 - comparison group. At the same time, in children of the main groups, a decrease in the concentration of IL-8 was observed, to the level of full-term newborns, and in children of the 1st group, the content of IL-6 was 2 times lower than in the comparison group (p1-3 = 0.001). As a result of our studies, we have demonstrated that the spectrum of monocyte-macrophage protection factors in children with ELBW at birth was significantly limited due to a decrease in adhesion and migration of cells to the inflammation focus (CD14+CD11b+, CD14+ CD64+), as well as the presentation of infectious pathogens (CD14HLA -DR), which indicates a violation of coordination between innate and adaptive immunity and may be the cause of the development of bacterial complications and a prolonged course of the inflammatory process. By the time of transfer of children with ELBW to the stage of early rehabilitation, the inclusion of effector mechanisms of the cellular link of immunity was established - an increase in the percentage of NK cells, the level of which remained after reaching PCA for 38-40 weeks. The ability of monocytes to recognize infectious pathogens and a full-fledged antigen-presenting function was restored. The number of cells expressing signaling molecules (CD11b and CD64) in children of the main groups did not differ, and the relative number of CD14+HLA-DR+ cells exceeded the indices of term infants both at the end of the neonatal period and in PCA 38-40 weeks. In the course of the immune response, the cytokine system - products of activated immunocompetent cells mediates the regulation of intercellular interactions. Another common feature of the innate immunity of children with ELBW is the predominance of pro-inflammatory cytokine factors in the cord blood serum that determine the nature of the immune response (Th1-dependent response): an increased concentration of IL-8 at birth and a decreased content of IL-4, which persists after reaching PCA 38- 40 weeks. Thus, the formation of the immune system response in the postnatal period of premature infants with ELBW does not depend on GA. The revealed highest content of serum IFN-γ, IL-6 and IL-8 in newborns at GA of 22-27 weeks at birth indicates the activation of the immune system in the antenatal period, due to the presence of risk factors for the development of infectious pathology of mothers (chorioamnionitis, prolonged anhydrous period, premature rupture of the membranes). 3.3. Evaluation of local immunity in children with extremely low body weight Intestinal microbiota formation is a multi-step process that plays an important role in the maturation of the immune system in newborn babies. To activate local immunity, as well as the immune system of the whole organism against the background of the formation of an adequate immune response, it is necessary to influence the antigens of the normoflora [1, 2]. There is evidence in the publication that in the second half of pregnancy, the intestinal microflora is formed in the fetus through the phenomenon of bacterial translocation [3]. Colonization of the intestine by microbiota determines the balance of T-helper cells (Th1 and Th2), while the prevalence of one pathway or another contributes to the development of atopic and infectious diseases. Under normal conditions, there is a regulation and selectivity of defense mechanisms that control intestinal colonization and determine either immunological tolerance or the development of an immune response to pathogens [4]. The pathological course of the ante- and intranatal periods, infection, morphofunctional immaturity, hypoxia and asphyxia, invasive medical procedures, delayed breastfeeding in children with ELBW contribute to impaired colonization of the gastrointestinal tract [4]. Colonization of the intestine by the microflora in term and premature infants has significant differences [5]. In children with ELBW, there is no transformation of the intestinal microbiota with the dominance of indigenous flora, especially in the provision of resuscitation care. Therefore, environmental factors become leading in the formation of microbial colonization. The leading places among various species are occupied by Coliforms, Enterococcus, Bacteroides, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Staphylococcus [5, 6]. In the reference, there are isolated works devoted to the study of systemic and local immunity in newborns with ELBW during early rehabilitation. After birth, under the influence of pathogens and immunological factors of breast milk, local immunity of the mucous membranes of the digestive tube is formed [7, 8, 9]. A number of studies have shown the relationship between increased IgA, IgM, IgG in blood serum and IgA, IgG in coprofiltrates in children from mothers with a long anhydrous period, STDs identified during pregnancy [10, 11]. By the end of the neonatal period, there was an increase in the frequency of detection of sIgA, IgG in coprofiltrates, as well as an increase in the concentration of serum immunoglobulins A and M. There is as well a decrease in immunoglobulin G in the blood serum in comparison with indicators at birth, which is possibly due to the destruction of maternal immunoglobulin G and the synthesis of own immune proteins [11]. There are practically no studies of the content of cytokines in coprofiltrates, which characterize the state of local immunity of children. The immaturity of the child's immune system is replenished by passive immunity transmitted from the mother to the newborn. Passive immunity is provided by maternal immunoglobulins and protective factors in breast milk. During the period of early microbial colonization of the intestine, the formation of the adaptive link of immunity begins in a child, a significant role in this process is assigned to bifidobacteria and lactobacilli, which trigger the production of cytokines by activated phagocytic cells [12]. Changes in the qualitative and/or quantitative composition of the intestinal microflora affect the Th1/Th2 balance of helper cells, determining immunological tolerance relative to normal microbiota or the immune response to pathogens [13]. By the time of transfer to the second stage of nursing, the intestines of children were colonized on average, in 70.8% of cases by pathogenetic microorganisms presented in Table 27. Table 27 Frequency of detection of opportunistic pathogens in feces in children with ELBW at the age of 1 month Microflora CFU/g 1 group (n=35) 2 group (n=40) Abs. % Abs. % Microflora not identified 10 28,5 12 30 Р1-2=0,003 Microflora identified 25 71,5 28 70 Р1-2=0,005 Enterobactеr сloacae < 105 2 5,7 0 0 >105 1 2,9 1 2,5 Enterobactеr aerogenes < 105 0 0 0 0 >105 0 0 2 5 Klebsiella pneumoniae < 105 1 2,9 1 2,5 >105 2 5,7 3 7,5 Klebsiella oxytoca < 105 0 0 0 0 >105 0 0 2 5 Escherichia coli < 105 0 0 0 0 >105 2 5,7 3 7,5 Stenotr. Maltophilia < 105 0 0 0 0 >105 1 2,9 1 2,5 Pseudomonas spp. < 105 2 5,7 0 0 >105 1 2,9 1 2,5 S. epidermidis < 105 6 17,1 4 10 >105 1 2,9 0 0 S. haemolyticus < 105 0 0 0 0 >105 0 0 3 7,5 Еnterococcus faecium < 105 2 5,7 4 10 >105 2 5,7 2 5 Genus of yeasts - Саndida < 105 1 2,9 0 0 >105 0 0 0 0 Mixed flora < 105 0 0 0 0 >105 1 2,9 1 2,5 Note. р1-2 - the significance of differences between groups of children (χ2 test with Yates' correction): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation. The frequency of detection of enterobacteria (Enterobacter cloacae, Klebsiella pneumoniae, Escherichia coli) and non-fermenting gram-negative bacteria (Stenotrophomonas maltophilia, Pseudomonas spp.) was 34.2% in group 1. The total share of gram-positive bacteria (Staphylococcus epidermidis, Enterococcus faecium) is 28.5%. The frequency of detection of gram-negative and gram-positive microorganisms was practically the same in group 2. Enterobacteriaceae (Enterobactеr сloacae, Enterobactеr aerogenes, Klebsiella pneumoniae, Klebsiella oxytoca, Escherichia coli) and non-fermenting gram-negative bacteria (Stenotrophomonas maltophilia, Pseudomonas spp.) were observed in 35% of cases. The detection rate of coagulase-negative staphylococci (Staphylococcus haemolyticus, Staphylococcus epidermidis) and enterococci (Enterococcus faecium) was 32.5%. Mixed flora was detected in both groups of children with almost the same frequency of 2.9% (Candida kruzei 105 and Staphylococcus epidermidis 105 CFU/g) and 2.5% (Klebsiella oxytoca 106 and Citrobacter frendii 106 CFU/g) cases, respectively. It should be noted that microorganisms of the Enterobacteriaceae family and non-fermenting bacteria (Stenotr. Maltophilia and Pseudomonas spp.), potentially dangerous in terms of the formation of antibiotic resistance, were detected in almost every fourth child of both groups (25.7% and 27.5%, respectively) By PKA 38-40 weeks, intestinal microflora was found in all children from group 1 (Table 28). Table 28 Frequency of detection of opportunistic microflora in feces in children with ELBW at the post-conceptional age of 38-40 weeks Microflora CFU/g 1 group (n=29) 2 group (n=29) Abs. % Abs. % Microflora not identified 0 0 7 24,1 Р1-2=0,003 Microflora identified 29 100 22 75,8 Р1-2=0,005 Enterobactеr сloacae < 105 0 0 0 0 >105 1 3,4 0 0 Klebsiella pneumoniae < 105 0 0 1 3,4 >105 6 20,7 3 10,3 Klebsiella oxytoca < 105 0 0 0 0 >105 2 6,9 1 3,4 Escherichia coli < 105 0 0 0 0 >105 3 10,3 2 6,9 Pseudomonas spp. < 105 0 0 1 3,4 >105 0 0 0 0 S. epidermidis < 105 4 13,8 1 3,4 >105 0 0 0 0 Еnterococcus faecium < 105 2 10,3 4 13,8 >105 3 10,3 1 3,4 Mixed flora < 105 2 6,9 2 6,9 >105 4 10,3 4 13,8 Note. р1-2 - significance of differences between groups of children (χ2 test with Yates' correction): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation. The total proportion of gram-positive microorganisms decreased to 17.2% of cases, and the detection rate of enterobacteriaceae and gram-negative non-fermenting bacteria increased to 62%. In the 2nd group of children, the intestines were colonized in 75.8% of cases. At the same time, the proportion of gram-negative microorganisms remained at the same level (34.4%), compared with the age of one month. The detection rate of coagulase-negative staphylococci and enterococci decreased 1.6 times and amounted to 20.7% of cases in both groups. The number of cases of microbial associations detected at the age of a full-term baby in groups 1 and 2 increased 7.1 and 8.2 times (20.6% of cases). The number of children with microorganisms of the family Enterobacteriaceae and non-fermenting bacteria in the 1st group increased by 12.2% (up to 37.9%), and in the 2nd group did not change and amounted to 27.5%. Thus, a decrease in the amount of coccal microflora and an increase in the proportion of opportunistic enterobacteria were observed, the release of which from feces by the post-conceptional age was 100% and 75.9% in both groups in all very premature infants with ELBW, against the background of systemic antibiotic therapy, upon reaching 1 month of life. Intestinal colonization by enterobacteriaceae and non-fermenting gram-negative bacteria in children of group 1 was 1.6 times higher than in children of group 2 (62% versus 38%). At the same time, in 24.1% of children of the 2nd group, the intestines were not colonized. The share of mixed intestinal flora in children of the 1st and 2nd groups increased to 20.7%. When analyzing the state of local immunity of children with ELBW, depending on the gestational age of the child, it was found that the content of IFN-γ in coprofiltrates in deeply premature infants during the entire stage of early rehabilitation significantly exceeded the indicators of the comparison group (Table 29). Table 29 The level of cytokines in the dynamics of the postnatal period in coprofiltrates in children with ELBW, IU (P25-P75) Indicators, pg/ml Age 1st group (n=42) 2nd group (n=43) 3rd group (n=25) Р IFN-γ 5-7 days 7,47(6,63-7,58) 6,42(6,10-7,05) 5,68(0-5,89) р1-3, 2-3=0,0001 1 month 6,32(5,48-7,06) 5,37(4,95-5,84) 5,68(0-5,89) р1-3, 2-3=0,0001 р1-2=0,09 PKA 38-40 6,22(5,23-7,27) 5,79(5,16-8,0) 5,68(0-5,89) р1-3, 2-3=0,0001 IL-6 5-7 days 3,0(2,66-3,12) 3,11(2,88-3,29) 6,12(5.54-6.47) р1-3, 2-3=0,0001 1 month 2,94(2,89-3,23) 3,1293,02-3,230 6,12(5.54-6.47) р1-3, 2-3=0,0001 р1-2=0,012 PKA 38-40 3,06(2,89-3,13) 3,12(2,89-3,29) 6,12(5.54-6.47) р1-3=0,06 р2-3=0,03 IL-8 5-7 days 2,23(2,18-3,85) 2,56(2,17-2,86) 5.81(2.82-5.9) р1-3, 2-3=0,0001 1 month 2,31(2,3-2,48) 2,22(2,18-2,55) 5.81(2.82-5.9) р1-3, 2-3=0,0001 PKA 38-40 2,44(2,2-3,85) 2,56(2,24-2,82) 5.81(2.82-5.9) Р2--3=0,001 IL-4 5-7 days 34,33(22,67) 31,49(25,91-46,95) 4,33 (3,24-4,48) р1-3, 2-3=0,0001 1 month 23,95 (16,69-34,08) 12,47 (2,31-60,18) 4,33 (3,24-4,48) р1-3, 2-3=0,010 PKA 38-40 32,33 (20,88-61,48) 35,39 (27,27-50,81) 4,33 (3,24-4,48) р1-3, 2-3=0,001 Note. р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation. There was a decreased content of IL-6 - statistically significant in the neonatal period and at the level of the tendency to PCA 38-40 weeks. The lowest concentration of this chemokine was observed in children of the 1st group at 1 month of age. In all children with ELBW in the early period of adaptation, there was a decrease in the concentration of IL-8, in children of the 2nd group, the revealed changes persisted until PCA 38-40 weeks. In the dynamics of the observation period from the first week of life, all premature infants had a significantly high content of IL-4. It may indicate the importance of opportunistic microorganisms, their species diversity in the activation of the humoral link of immunity, the implementation of local protective mechanisms (activation of chemotaxis, limitation of the focus of inflammation, increasing the cytotoxic ability of macrophages). The degree of protection against bacterial and viral infections of the gastrointestinal tract depends on the sIgA content, the main function of which is to neutralize toxins and viruses. Increased production indicates the development of an infectious process. As a result of the studies, it was found that the content of the sIgA level in coprofiltrates in children with ELBW at different periods of the study exceeded the standard values (0.5-2.0 g / l), which may be due to the activation of humoral immunity in the antenatal period (Table 30). Table 30 The content of sIgA in coprofilters in children with ELBW in the dynamics of the postnatal period, g/l Time schedule 1st group (n=42) 2nd group (n=43) 3rd group (n=25) Significance level 5-7 days 9,07(6,94-12,82) 12,67(6,53-13,70) 1,08(1,03-3,36) Р1-3, 2-3=0,0001 Р1-2=0,09 1 month 10,44(8,89-10,97) 9,7(9,58-10,71) 1,08(1,03-3,36) Р1-3, 2-3=0,0001 PCA 38-40 weeks 10,03(5,97-11,12) 8,77(6,5-10,02) 1,08(1,03-3,36) Р1-3, 2-3=0,0001 Note. р1-2 - significance of differences between groups of children (Mann-Whitney test): 1 - children, 22 - 27 weeks of gestation, 2 - children 28 - 31 weeks of gestation. It should be noted that on the 5-7th day of life in children of gestational age of 22-27 weeks, there was a tendency to an increase in sIgA, compared with the indicators of newborns of the 2nd group. In further periods of life there were no significant differences between the main groups of children. When conducting correlation analysis, it was found that the presence of opportunistic microflora in the intestine of a child in the early neonatal period positively correlates with the sIgA level in coprofiltrates at the age of 1 month of life (r = 0.32, p = 0.04), as well as with the content of IL-4 in 38-40 weeks of PCA. It is known that breast milk is characterized by a high content of sIgA, the main function of which is to protect the GIT mucus membrane from pathogens of intestinal infections. We found direct correlations between breast milk production when feeding children with conditionally pathogenic intestinal microflora in the early neonatal period and at the age of 1 month of life with sIgA level in coprofiltrates (r = 0.76 and r = 0.67 at, p = 0.001 ). It possibly indicates the infection of the child in the antenatal period with the help of the phenomenon of bacterial translocation, when the maternal microorganisms entering the fetus in the second half of pregnancy cause the formation of an immune response. By the time of transfer to the stage of early rehabilitation in premature infants with ELBW against the background of systemic antibacterial, intestinal microbiota was disturbed in 71.5 and 70% of cases of children of both groups. Upon reaching PCA 38-40 weeks in children from very early preterm birth, the frequency of detecting a violation of the microbial landscape increased 1.4 times, and in children from early preterm labor remained at the same level (100% and 75.8%, p = 0.005 in 1 -th and 2nd groups, respectively). Thus, intestinal colonization by opportunistic microflora in all premature infants in the dynamics of the postnatal period was accompanied by an increase in the concentration of IFN-γ and IL-4, and a decrease in the content of IL-6 and IL-8 against the background of an increase in sIgA production in coprofiltrates. It indicates the development of humoral response and is confirmed by the presence of positive correlations between the level of sIgA in coprofiltrates at the age of 1 month of life and the content of IL-4 at 38-40 weeks of PCA. It should be noted that an increase in the frequency of detecting a violation of the microbial landscape in children from very early preterm birth is apparently associated with a 4.5-fold decrease in the number of children breastfed by 38-40 weeks of PCA, in contrast to children from early preterm birth. A decrease in the content of sIgA in coprofiltrates in children with GA of 28-31 weeks indicates a reduced need for this immunoglobulin due to the elimination of microorganisms in 38-40 weeks of PCA compared with one month of age. The concentration of anti-inflammatory IL-4 in children from early preterm birth during this period practically did not change compared with one month of age, and in children from very early preterm birth it increased 1.4 times. It indicates the activation of humoral reactions in response to the introduction of conditional pathogenic microorganisms.

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