The effect of preimmunization of CBA/H mice with M locus and H-2 incompatible lymphocytes was examined on the in vitro generation of cytotoxic cells to both types of targets. Preimmunization with M locus did not help to generate cytotoxic cells to M-locus targets; however, the anti-H-2 cytotoxicity of M-locus-preimmunized lymphocytes was suppressed between the 6th and 19th day after preimmunization. In contrast, preimmunization with H-2 incompatibility produced an amplified lytic anti-H-2 response. The possible mechanisms are discussed.

No abstract

S U M M A R YTwenty-six combinations of C57BL/10 congenic mice involving incompatibilities in the I region and the H-2K or H-2D regions of the major histocompatibility complex were studied in a cell-mediated lympholysis assay (CML). All combinations were positive ; however, six were unidirectional. Three of these were consistent with the mapping of an effector cell stimulating locus (ECS) between the IB and IC sub-regions. Possible reasons are given for the negativity of CML in I/H-2K or H-2D region incompatible combinations. A statistical method used to analyse the data is described.