Influence of age on the proliferation and peripheralization of thymic T cells.
Bone marrow cells obtained from B10.Thy-1.1 mice (H-2b, Thy-1.1) were injected directly into the thymus of C57BL/6 mice (H-2b,Thy 1.2) of various ages. Thymocyte precursors in the injected donor-bone marrow cells could proliferate in the thymic microenvironment in the following manner: first, preferentially proliferating into the subcapsular cortex; and second, spreading to the whole layer of the cortex, a portion of them gradually moving into the medulla. The proliferation of donor-type thymocytes was most pronounced when intrathymic injection of bone marrow cells (ITB) was performed in newborn mice and especially prominent in week-old mice; it took approximately ten weeks for donor-type thymocytes to finish the whole course of proliferation, differentiation, and emigration to the periphery. When ITB was performed in mice 4 weeks of age and older, the proliferation of donor-type thymocytes was retarded at onset, less pronounced in magnitude, and disappeared earlier. Emigration of donor-type T cells from the thymus to the peripheral lymphoid tissues occurred most rapidly when ITB was performed in newborn mice, and these T cells continued to reside thereafter in the peripheral lymphoid tissues. However, when ITB was performed in mice 4 weeks of age and older, the number of emigrated T cells in the spleen decreased (about a tenth of that in newborn mice) and, moreover, these T cells resided only transiently in the spleen. It was suggested that T cells emigrating from the thymus of mice from newborn to 2 weeks of age are long-lived, whereas those from the thymus in mice 4 weeks of age and older are short-lived. However, when 4-week-old young adult mice were treated by irradiation or hydrocortisone, the thymic capacity was enhanced in terms of proliferation and peripheralization of thymocytes, and emigrated T cells became long-lived.
Hirokawa
K
K
Department of Pathology, Tokyo Metropolitan Institute of Gerontology, Japan.
Utsuyama
M
M
Katsura
Y
Y
Sado
T
T
D000305:Adrenal Cortex Hormones / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000818:Animals; D001854:Bone Marrow Cells; D016026:Bone Marrow Transplantation; D002455:Cell Division; D002465:Cell Movement; D005434:Flow Cytometry; D007150:Immunohistochemistry; D007267:Injections; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D013950:Thymus Gland / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects
D000305:Adrenal Cortex Hormones