A strong,preferential response of mice to polymorphic antigenic determinants of the chicken MHC,analyzed with mouse hybridoma (monoclonal) antibodies

CBA/J mice were immunized with B²/B² chicken RBC's (theB locus is the major histocompatibility complex (MHC) of the chicken). Spleen cells from these mice gave a much higher plaque-forming cell response when tested with RBC's bearing B² alloantigens, than with RBC's bearing any other MHC alloantigens. Similarly, immunization with chicken RBC's of other genotypes also produced responses that were highest when tested on the genotype used for immunization. Spleen cells from mice immunized 3 days previously with B²/B² RBC's were fused with mouse myeloma cells and hybrid clones which secreted anti-B² antibodies were selected. These monoclonal antibodies could be divided into three groups: (1) those which react with all genotypes of RBC's (panreactive); (2) those which react with only certain genotypes of RBC's and detect “public” MHC antigens; and (3) those which react with only B²/B² RBC's and detect “private” MHC antigens. Monoclonal antibodies which detect a private B² alloantigen were shown to be excellent typing reagents, as all birds of an outbred population which possessed the B² allele were easily detected using a simple one-step direct agglutination assay. No “false positives” were seen. The high and preferential response of the mouse to chicken MHC alloantigens suggested that mice might possess preexisting immunity to these antigens. In agreement with this hypothesis, normal mouse serum was found to have high titres of “natural” antibody against chicken MHC antigens.