Complexity of the histocompatibility-3 region in the mouse.

Congenic lines C57BL/10Sn (H-3a), B10.LP-H-3b, B10.C-H-3c, and B10.KR-H-3d were arranged into the 12 possible recipient-donor combinations and immunized. The spleen cells of each recipient were then tested for the presence of cytolytic effector T lymphocytes (CTL) specific for antigenic determinants controlled by the H-3 locus and restricted by class I H-2 loci. The strain-distribution pattern of the determinants defined by the individual CTL was determined by direct testing and by cold-target inhibition analysis. The restriction elements of the individual determinants were identified by the testing of H-2 recombinant strains and by antibody blocking. Five determinants were identified: 1 and 2, restricted by the Db molecule; 3 and 4 restricted by the Kb molecule; and 5, for which the restriction molecule could not be determined. The distribution pattern of determinants 3 and 4 correlated with the distribution of alleles at the beta 2-microglobulin locus. The data could be interpreted as arguing for the existence of three loci in the H-3 complex, with one coding for mutually antithetical determinants 1 and 2, another coding for mutually antithetical determinants 3 and 4, and still another coding for determinant 5.