Functional Characteristics of Neonatal Naive T cell and Their Maturation into Memory T cell

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Naive and memory T cell populations can be discriminated by differential expression of CD45 isoforms. These studies were undertaken to elucidate some functional characteristics of neonatal inherently naive T cells and their maturation steps into memory T cells following increased antigenic exposure after birth. Obtained results are follow as.1) Although neonatal T cells share with adult naive T cells in terms to CD45RA expression, they have strong suppressor activity and less helper activity for B cell differentiation even after memory cells-like phenotypic changes by activation.2) BB3^+ subsets within T-gamma/delta^+ T cells, but not deltaTCS-1^+ cells, express CD45RO and have the ability to respond to the antigen.3) Naive CD4^+ T cells, unlike memory ones, are hyporesponsive to anti-CD2 stimulation, based on their inability to produce IL-6.4) Both CD4^+ and CD8^+ T cell populations express CD45RO as well as HLA-DR antigens, indicating strong stimulation with Epstein-Barr infection.5) Memory T cells express IL-2 receptor subunits (alpha or chains) and respond well to exogenous IL-2.6) A novel population of CD4^+ T cells with naive (CD45RA^+, CD45RO^-) phenotype expressing IL-2R alpha-chain, which express memory-like functions, are identifiable in the blood of newborns and young children. This population represents the cells at the transitional stage from naive to memory T cells.7) Full-term newborns can produce IL-6 in response to bacterial pathogens, but IL-6-producing capabilities of preterm babies are still immature.