title: Ontogeny and characterization of mitogen-reactive lymphocytes in the thymus and spleen of the amphibian, Xenopus laevis.
abstract: The ontogeny of the proliferative response of Xenopus thymocytes to the T-cell mitogens concanavalin A (Con A) and phytohaemagglutinin and to the B-cell mitogen E. coli lipopolysaccharide (LPS) is examined during the first 2 years of life. Responses after metamorphosis are compared with those occurring in the spleen. During much of larval life, mitogen-treated thymocytes display no sign of elevated [3H]TdR uptake. A low level in vitro response to Con A and LPS emerges transiently just prior to metamorphosis, the latter period being associated with a temporary disruption of thymocyte mitogen reactivity. Appreciable stimulation of both thymocytes and splenocytes with all three mitogens emerges within the first few months post-metamorphosis, and, with the exception of the thymocyte response to LPS, these induced proliferative levels are maintained or increased in toadlets aged 7-24 months. Maximal levels of LPS responsiveness in thymocyte cultures are found at 6 months of age. LPS-induced thymocyte proliferation at this time is confirmed morphologically by autoradiography; furthermore, immunofluorescence experiments, using an anti-Xenopus-mu chain antiserum, reveal that LPS induces the differentiation of cytoplasmic IgM cells in both spleen and thymus. The results indicate the presence of substantial populations of mitogen-sensitive cells in B lineage in the anuran thymus.
mesh_terms: D000375:Aging; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D003208:Concanavalin A / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000276:immunology*; D010835:Phytohemagglutinins / Q000494:pharmacology; D013154:Spleen / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology*; D014982:Xenopus laevis / Q000276:immunology*
chemical_list: D008070:Lipopolysaccharides; D010835:Phytohemagglutinins; D003208:Concanavalin A