Monoclonal antibodies to guinea pig Ia antigens. I. Production, serologic, and immunochemical characterization.

Xenogeneic antibodies to guinea pig Ia antigens were produced by application of the hybridoma technique. BALB/c mice were immunized with the Ia-positive B cell leukemia line EN-L2C of strain 2 guinea pigs, and the spleen cells were fused to the mouse myeloma line NS-1. Culture supernatants of hybrids growing in the selective HAT medium were screened in a binding assay, and hybrids selectively reactive with EN-L2C but not with its Ia-negative variant BZ-L2C were cloned. Ascitic fluid was produced and used as a source of antibody. Four independently derived antibodies proved to be specific for Ia antigens. Two of the antibodies (25E3 and 25E11) seemed to recognize alloantigenic determinants on strain 2 Ia antigens in that they bound only to the cells of strain 2 but not to the cells of strain 13 animals. Two other antibodies (22C4 and 27E7) were found to react with both strain 2 and strain 13 cells, and immunoprecipitation experiments revealed that these antibodies were directed to common determinants shared between certain strain 2 and strain 13 Ia antigens. All antibodies were cytotoxic in the presence of complement for EN-L2C (but not for BZ-L2C) leukemia cells and for lymph node, spleen, peritoneal exudate cells, thymocytes, and purified T cells of strain 2 guinea pigs. In addition, 22C4 was cytolytic for cells of both strains. These results indicate that antibodies can be obtained through the hybridoma technique that are able to distinguish different determinants on Ia antigen molecules of te guinea pig. These antibodies should provide a useful tool for further study of the role of Ia antigens in cellular interaction and Ia-Ir gene function.