Residual minor histocompatibility genes contaminate the B10.AM congenic line: no evidence of C-region-controlled histoincompatibility.

After being primed in vivo and restimulated in vitro, cytolytic T lymphocytes (CTL) were produced in the strain combinations B10.AM anti-B10.A(1R) and B10.A(1R) anti-B10.AM. Although the two strains differ in the chromosomal interval between the E alpha and the D loci, the CTL are not directed against antigens controlled by loci in this interval. Instead, the CTL detect minor histocompatibility (H) antigens controlled by loci that are not linked to H-2. The recognition of the antigens detected by the B10.AM anti-B10.A(1R) CTL is restricted by the Kk and Db molecules, but the CTL also cross-react with the Dd molecule (or a molecule controlled by a locus closely linked to Dd). The recognition of the antigens detected by these two CTL behave as if controlled by alleles at the same minor H locus or loci. This locus is distinct from H-2, and the B10.AM congenic line apparently retained a C3H-derived allele at this locus.