Differences in the MHC-restricted self-recognition repertoire of intra-thymic and extra-thymic cytotoxic T lymphocyte precursors.

The MHC specificity of TNP-specific pCTL from the thymus and spleen of F1 leads to parent chimeras was evaluated. It was found that in the presence of exogenously added helper factor IL 2, thymic pCTL were restricted to recognizing TNP only in association with host MHC determinants, whereas splenic pCTL recognized TNP in association with either host or donor MHC determinants. Thus, the spleens of F1 leads to parent chimeras contain a pCTL repertoire that is not present intrathymically. Data are presented which suggest that such pCTL did nevertheless differentiate into functional competence in the chimeric host. These results are consistent with extra-thymic differentiation as the mechanism by which such nonthymically restricted pCTL may have developed.