Thymic epithelium induces neither clonal deletion nor anergy to Mls 1a antigens

Abstract

Grafting of thymic anlagen from day-10 DBA/2 (H-2d; Mls-1a) embryos to newborn athymic BALB/c (H-2d; Mls-1b) mice leads to reconstitution of T cell populations in the recipients. Analysis of adult chimeras shows that their V beta T cell receptor (TcR) repertoires, particularly V beta 6 and V beta 8.1, do not significantly differ in most animals (10 out of 13) from those scored in control chimeras that received syngeneic thymic anlagen. In all cases analyzed, such Mls-1a-reactive T cells could be stimulated at levels comparable to control responses, both in vitro and in vivo. The few cases in which Mls-1a reactive V beta TcR were reduced seem to reflect the variability in TcR V beta repertoires found in this experimental system. In contrast, BALB/c mice, injected at birth with DBA/2 spleen cells show a marked, albeit variable, reduction in the frequencies of V beta 6- and V beta 8.1-bearing CD4+ T cells, and lower frequencies of Mls-1a-reactive T cells in limiting dilution analyses. It appears, however, that V beta 6- and V beta 8.1-bearing T cells remaining in these mice are functionally competent. We conclude that Mls-1 antigens are not expressed by thymic epithelium.