Selection of the T-cell repertoire during ontogeny.

This report examines conflicting hypotheses concerning T-cell repertoire selection in terms of H-2 restriction during ontogeny. The experiments described in this report were incompatible with the hypothesis that bias in the repertoire is solely a consequence of "more or less intentional priming" by foreign antigen. Rather, results indicate that the repertoire is selected by self major histocompatibility complex (MHC) antigens in the absence of foreign antigens. Allorestricted T cells, the existence of which was previously thought to be incompatible with the concept of complete repertoire selection by self MHC antigens, were shown to significantly cross-react on targets expressing self MHC antigens. Thus, it is possible that allorestricted T cells are simply cross-reactive T-cell clones restricted by self MHC antigens; indeed, all experimental data were compatible with the idea of complete selection of the T-cell repertoire in terms of H-2 restriction by self MHC antigens.