Immunological aspects of aging: early changes in thymic activity.
Age related changes in immune function are preceded by changes in thymic function. One index of thymic function is the ability of the thymus to induce the differentiation of bone marrow pre-T cells into active T cells. Movement of precursors of PHA-responsive T cells into the thymus ceases prior to adolescence in long-lived, autoimmune disease resistant mice as determined by studies utilizing chromosome markers in parabiotic mice. The cause for this age-dependent, cell traffic phenomenon is not known, but it would appear that an extrathymic regulatory mechanism may be operating, since these precursor T cells have the capacity to migrate into the thymus, and even a grafted, involuting thymus is capable of accepting precursor T cells, under extraordinary conditions. Results indicate that shortly after adolescence, immature T cell precursors of PHA-responsive cells in the thymus, and perhaps the periphery, are the sole source of PHA-responsive T cells. T cell migration and maturation is discussed in relation to thymic hormones and the thymic-neuroendocrine regulatory axis.
D000375:Aging; D000818:Animals; D002454:Cell Differentiation; D002465:Cell Movement; D006410:Hematopoiesis; D008221:Lymphoid Tissue / Q000166:cytology / Q000276:immunology; D051379:Mice; D008808:Mice, Inbred CBA; D010227:Parabiosis; D010835:Phytohemagglutinins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology*
D010835:Phytohemagglutinins