title: Post-thymic T lymphocyte maturation during ontogenesis.
abstract: Peripheral T lymphocytes from newborn (4-6-d-old) mice, isolated from the spleen or lymph nodes, show phenotypic features of immature cortical thymocytes, such as high frequencies of proliferating cells and of peanut lectin-binding cells. These are features of peripheral T cells of recent thymic origin, as shown by in situ labeling of thymocytes and subsequent observation of the migrants to the spleen, which were mainly peanut lectin-binding cells. The function of newborn peripheral T cells was compared, on a per T cell basis, with that of thymocytes and of fully mature peripheral T cells of the adult, using preparations of newborn lymph node cells containing approximately 80% of T lymphocytes. They were strikingly (about 10-fold) less competent than adult T cells in their phytohemagglutinin responsiveness, their capacities to induce a graft vs. host reaction, to proliferate in the mixed lymphocyte reaction, and to help B lymphocytes in a humoral response in vivo and in vitro. In contrast, newborn T lymphocytes were comparable to those of adults in their capacity to generate cytotoxic T lymphocytes. No suppressive effect of newborn T lymphocytes could be demonstrated in several of these assays. These results argue for an asynchronous maturation of two T cell subsets during ontogeny and demonstrate that at least some T lymphocytes leave the thymus as immature T cells resembling cortical thymocytes and further mature at the periphery. Investigation of mice submitted to thymectomy of 5 d of age showed that these incompetent post-thymic T lymphocytes are capable of considerable expansion and maturation in the peripheral lymphoid organs in the absence of a thymic influence.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000276:immunology*; D000917:Antibody Formation; D000954:Antigens, Surface / Q000032:analysis; D002454:Cell Differentiation; D002478:Cells, Cultured; D006087:Graft vs Host Reaction; D037102:Lectins / Q000494:pharmacology; D008198:Lymph Nodes / Q000276:immunology; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008565:Membrane Proteins / Q000032:analysis; D051379:Mice; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D018800:Thy-1 Antigens; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D000954:Antigens, Surface; D037102:Lectins; D008565:Membrane Proteins; D018800:Thy-1 Antigens