title: Cellular and molecular mechanisms for reduced interleukin 4 and interferon-gamma production by neonatal T cells.
abstract: The mechanisms by which T lymphocytes acquire the capacity to produce interleukin 4 (IL-4) and other lymphokines during intrathymic and extrathymic development are poorly understood. To gain insight into this process, we determined the capacity of human neonatal and adult T lineage cell populations to produce IL-4 after polyclonal activation. IL-2 and interferon-gamma (IFN-gamma) production were studied in parallel, since their production by neonatal T cells is known to be similar or diminished, respectively, compared to adult T cells. Production of IL-4 by neonatal CD4+ T cells and IFN-gamma by neonatal CD4+ and CD8+ T cells was markedly lower compared with analogous adult cell populations, whereas IL-2 production was similar. Transcription of IL-4, as determined by nuclear run-on assays, and IL-4 mRNA-containing cells, as determined by in situ hybridization, were undetectable in neonatal T cells, whereas both were detectable in adult T cells. IFN-gamma transcription and IFN-gamma mRNA-containing cells were reduced in neonatal T cells compared with adult T cells. Reduced lymphokine production by neonatal T cells correlated with their lack of a CD45R- (putative memory T cell) population; cells with this surface phenotype comprised 30-40% of the adult CD4+ T cells and were highly enriched for IL-4 and IFN-gamma, but not IL-2 production. IL-4, IFN-gamma, and IL-2 mRNA expression by neonatal CD4+CD8- thymocytes was similar to that found in circulating neonatal CD4+ T cells. Taken together, these findings suggest that the extrathymic generation of memory T cells during postnatal life may result in an increased capacity for IL-4 and IFN-gamma gene expression. In addition, IFN-gamma and IL-2 mRNA were significantly more abundant than IL-4 mRNA in activated neonatal CD4+CD8- thymocytes and CD4+ T cells, as well as adult CD4+ CD45R- T cells. Therefore, the capacity of T lineage cells to express the IL-4 gene may be more restricted compared to other lymphokine genes beginning in intrathymic development. This restricted capacity appears to persist during postnatal extrathymic maturation of T cells.
authors.affiliation: Department of Pediatrics, University of Washington, Seattle 98105.
authors.forename: D B
authors.initials: DB
authors.lastname: Lewis
authors.forename: C C
authors.initials: CC
authors.lastname: Yu
authors.forename: J
authors.initials: J
authors.lastname: Meyer
authors.forename: B K
authors.initials: BK
authors.lastname: English
authors.forename: S J
authors.initials: SJ
authors.lastname: Kahn
authors.forename: C B
authors.initials: CB
authors.lastname: Wilson
mesh_terms: D000328:Adult; D000943:Antigens, Differentiation / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens; D005312:Fetal Blood / Q000276:immunology*; D006649:Histocompatibility Antigens / Q000032:analysis; D006801:Humans; D007231:Infant, Newborn; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000235:genetics; D007376:Interleukin-2 / Q000235:genetics; D015847:Interleukin-4 / Q000096:biosynthesis* / Q000235:genetics; D017493:Leukocyte Common Antigens; D012333:RNA, Messenger / Q000032:analysis; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens; D016827:CD8 Antigens; D006649:Histocompatibility Antigens; D007376:Interleukin-2; D012333:RNA, Messenger; D015847:Interleukin-4; D007371:Interferon-gamma; D017493:Leukocyte Common Antigens