FEATURES OF PHENOTYPIC STRUCTURE AND FUNCTIONAL ACTIVITY OF CORD BLOOD IMMUNE CELLS DEPENDING ON GESTATIONAL AGE

The aim of our study was to identify phenotypic composition and functional activity of immune cells from umbilical cord blood (UCB) as a function of gestational age. We analyzed 102 UCB samples of babies born at 25-28 weeks, 29-32 weeks, and 33-36 weeks of gestation, and 31 samples of UCB from the full-term infants taken as a comparison group (gestational age of 37 to 41 weeks). Using flow cytometry approach, we determined representation of cells with CD3+-, CD19+/CD3-, CD4+/CD3+, CD8+/CD3+, CD16/56+/CD3-phenotypes, along with expression of activation markers among populations of monocytes and lymphocytes (HLA-DR+/CD14+, CD71+/CD14+, CD25+/CD4+, CD95+/CD3+), as well as adhesion receptors (CD11b+). Contents of cytokine-producing cells (IL-4/CD4, IFNγ/CD4) and serum IFNγ and IL-4 cytokines were also determined. All premature babies with existing leukopenia exhibited an increase in relative numbers of lymphocytes, and diminished ability of the granulocytes to absorb opsonized bacteria. Reduced percentage of HLA-DR+/CD14+ cells, increase in CD3+CD95+ cell population and IFNγ producing cells have been shown in a subgroup of children at a gestational age of 25-28 weeks. Decreased levels of natural killer cells was observed among infants < 32 weeks of gestation. Increased concentration of serum IFNγ, along with reduced levels of IL-4 was determined in children born at 25 to 28 and 33 to 36 weeks. A reduced percentage of CD3+CD11b+ cells were revealed in UCB at 29-32 and 33-36 weeks of gestation. Reduced numbers of CD3+CD95+lymphocytes and increased CD25+ receptor expression on the CD4+ cell population was registered at 33 to 36 weeks of gestation. In summary, the findings suggest some features of immune system, which may be specific to particular gestational age of preterm infants. A number of the parameters under study allow us to presume a development of partial immunological response to potential antigens, thus requiring further research aimed for investigation of functional activity of immunocompetent cells.

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