The ability of M. arthritidis, a potent arthritogenic agent, to induce normal unsensitized lymphocytes to undergo blast transformation and to become nonspecifically cytotoxic for syngeneic and allogeneic target fibroblasts was found to be dependent upon the donor strain of mouse. Lymphocytes from CBA (H2k) and BALB/c (H2d) mice were identified as high responders and lymphocytes from C56BL/10 mice (H2b) as low or nonresponders. In the cytotoxicity assay the extent of cell lysis was dependent

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... the origin of both the effector cell and the target cell. By comparing the ability of M. arthritidis to activate lymphocytes from various congenic and H-2 recombinant mouse strains we demonstrated that control of the degree of responsiveness was determined by the H2 gene complex. Further studies revealed that the region controlling induction of cytotoxic lymphocytes is located to the right of the I-J subregion and to the left of the D region, most probably the I-E and/or I-C subregions of the major histocompatibility complex. These observations may be of importance in regard to the susceptibility of different mouse strains to the pathogenic effects of M. arthritidis.