Thymic T cell export is not influenced by the peripheral T cell pool

Abstract

The peripheral T cell pool is maintained both by export of naive T cells from the thymus and by post-thymic expansion of activated/memory T cells. However, it is not known whether the thymus can alter its output following peripheral T cell depletion. Using intrathymic injection of fluorescein isothiocyanate to detect recent thymic emigrants (RTE), we directly tested whether the thymus is able to alter the number of RTE or the CD4:CD8 ratio of RTE emigrating to the periphery in response to in vivo depletion of total peripheral T cells or CD4 T cells, respectively. Depletion of peripheral T cells was achieved with anti-Thy-1 or anti-CD4, at doses that did not affect thymocyte numbers. Depletio..