Ontogeny of T lymphocyte function in the neonate.
T cell precursors are first detected in the thymus at eight weeks of gestation. By 15 to 20 weeks of gestation, T-cell precursors expressing alpha beta and gamma delta T-cell receptors are present in the thymus in numbers relatively similar to those found in postnatal life. However, recent data suggest that T-cell receptor diversity is more limited during fetal and neonatal life than in adults. Additionally, the functional capacity of T cells in the fetus and neonate is immature, in that neonatal T cells express a limited repertoire of lymphokines in response to activation. Specifically, the production of the lymphokines, interferon-gamma and interleukin-4, which participate in the maturation of cytotoxic cells, activation of macrophages, and the maturation and modulation of B cell function and isotype expression, is reduced more than tenfold compared to cells from adults. This appears to result primarily from the lack of memory T cells in the fetus and neonate, reflecting their antigenic naivete. The difference in lymphokine expression is due to diminished transcription of these genes in neonatal T cells in response to activation. Preliminary data indicate that differences in essential promoter elements regulating transcription of these lymphokine genes plays a role in their differential expression in T cells.
Wilson
C B
CB
Department of Pediatrics, University of Washington School of Medicine, Seattle.
Penix
L
L
Weaver
W M
WM
Melvin
A
A
Lewis
D B
DB
D000818:Animals; D000831:Animals, Newborn / Q000276:immunology; D015703:Antigens, CD / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007156:Immunologic Memory; D007231:Infant, Newborn / Q000276:immunology*; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000096:biosynthesis / Q000235:genetics; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000196:embryology / Q000254:growth & development*; D014158:Transcription, Genetic
D015703:Antigens, CD; D008222:Lymphokines; D011948:Receptors, Antigen, T-Cell