H-2 restriction and H-2 phenotypes of spleen cells from thymus-grafted radiation chimeras: evidence consistent with extrathymic suppression.

As an approach to analyzing the factors that contribute to determining H-2 restriction specificities of cytotoxic T cells, thymectomized semiallogeneic radiation chimeras were given transplants of fetal thymus from parental strain or F1 hybrid donors. A pronounced preference for lysis of infected targets of the same H-2 haplotype as the thymus was observed, the bias ranging from an undetectable preference through to absolute restriction to the thymic H-2. Virus-immune Tc cells could also be restricted to H-2 antigenic determinants of haplotypes expressed only by donated stem cell progeny lymphomyeloid cells. T cells from chimeras that had received thymuses of both parental strains were less effective than normal syngeneic F1 hybrid T cells in lysing allogeneic cells and both infected and uninfected parental targets. Variation in H-2 restriction bias from one chimera to another was not reflected in modulations to the class I H-2 phenotypes of the chimeric spleen cells.