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.

Rat Peripheral CD4+CD8+ T Lymphocytes Are Partially Immunocompetent Thymus-Derived Cells That Undergo Post-Thymic Maturation to Become Functionally Mature CD4+ T Lymphocytes

“…Therefore, we can conclude that rat peripheral DP lymphocytes are partially immunocompetent T cells that belong to the CD4 cell lineage and undergo post-thymic phenotypic and functional maturation in the peripheral lymphoid tissues. Similar post-thymic differentiation processes affecting CD4 ϩ T cells have been previously reported in mice and rats (44,54,55) and have been shown to be independent of the presence of the thymus (44,56), a fact also confirmed by our results. The nature of the signal(s) required for post-thymic development of some CD4 ϩ T cells is unknown at present.…”

Enhancement of antibody synthesis in rats by feeding cis-9,trans-11 conjugated linoleic acid during early life

“…The neonatal immune functionality of mammals is very limited, and during early life, it gradually starts to acquire the immune status of adults [32,33]. The impact of nutritional fatty acids on the development of the early immune system has been demonstrated to involve regulation of metabolic processes and gene expression of important proteins such as enzymes and cytokines [34].…”

Homeostasis of Peripheral CD4+ T Cells: IL-2Rα and IL-2 Shape a Population of Regulatory Cells That Controls CD4+ T Cell Numbers

“…Peripheral T cells, in absence of a thymus (4,25) or when transferred to T cell-deficient hosts (5,7,26), are capable of considerable expansion. The sequential transfer of a T cell population into successive hosts has shown that one T cell can generate up to 10 15 cells (7).…”