Thymidine Incorporation in Mixed Cultures of Spleen Cells From Mice of Differing H-2 Types

SUMMARY Normal murine spleen cells were cultured with syngeneic, allogeneic, or hemiallogeneic spleen cells that had been treated with mitomycin- C; subsequent incorporation of tritiated thymidine was measured. Cell donors were genetically alike except for differences at the H-2 locus. When mitomycin-treated cells were mixed with normal cells, thymidine incorporation in allogeneic cultures significantly exceeded that in hemiallogeneic cultures; incorporation in both allogeneic and hemiallogeneic cultures was significantly greater than in syngeneic cultures. No significant difference could be demonstrated between groups of parent-vs.-Fi and Fr-vs.-parent cultures, nor between reciprocal allogeneic combinations. The results support the conclusion that antigenic disparity can induce DNA synthesis in splenic cells in mixed cultures. Conventional immunological incompatibility alone is insufficient to explain all of the results. The ability of the mixed-culture test to distinguish homozygous and hemizygous differences in dosage of antigens did not extend to the recognition of differences in number or in strength of antigens defined by serological tests.