Genetic resistance of CBA and A mice to transplanted lymphoid and hemopoietic cells of CBA.M523 mutants and their F1 hybrids.

(CBA X M523)F1, (A X M523)F1 and M523 lymphocytes grafted into lethally irradiated CBA or A mice temporarily lose their capacity to respond to test antigens (SRBC, Vi-antigen, S. typhi). Immunoresponsiveness of F1 cells is affected to a lesser degree in lethally irradiated M523 mice. Depression of response is absent in the CBA leads to F1 combination, in the syngeneic combination and in CBA mice whch have received transplanted cells from F1 hybrids which do not share the M523 mutation. The number of hemopoietic (CBA X M523)F1 colonies was also reduced in CBA mice. Resistance of CBA mice to lymphoid (CBA X M523)F1 cells develops 18 days after birth. It can be reduced by additional recipient preirradiation or preinoculation with (CBA X M523)F1 spleen cells. The abrogated resistance can be partially restored by CBA spleen cells. The activity of (CBA X M523)F1 lymphocytes passaged through CBA spleen is restored in syngeneic F1 secondary recipients but inhibited again in the CBA secondary recipients. These results are consistent with the suggestion that resistance of lethally irradiated CBA mice to hemopoietic and lymphoid (CBA X M523)F1 cells is mediated by immunologically competent, radioresistant recipient cells rapidly reacting to transplantation antigens coded by the mutant H-2Kka allele. These cells temporarily suppress the functional activity of transplanted cells but do not eliminate them.