A study of the heterogeneity of human alpha 1-acid glycoprotein with monoclonal antibodies

Monoclonal antibodies (MABS) were raised against human alpha 1-acid glycoprotein (AGP) and their reaction with the polymorphic forms of this plasma protein were evaluated. Spleen cells of BALB/c mice, immunized with native or desialylated human AGP, were fused with NSO mouse myeloma cells. The hybridoma products were screened with a direct ELISA test, in which the immunoplates were coated with a mixture of native and desialylated AGP. In this test, 14 anti-AGP antibody producing clones were retained. Coating the wells with either native or desialylated AGP showed that eleven clones reacted with both types of AGP ('Type I' MABS), while three MABS reacted specifically with the desialylated form ('Type II' MABS). Precoating the immunoplates with polyclonal anti-human AGP followed by incubation with native or desialylated AGP before the addition of hybridoma supernatant (indirect ELISA), confirmed the specificities observed in the direct ELISA. The molecular heterogeneity of both native AGP and desialylated AGP, based on Concanavalin A reactivity and isoelectric point, was not reflected by any specificity in the antibody reactions. Thus 'Type I' MABS reacted with all molecular forms present in native and desialylated AGP while 'Type II' MABS reacted with all molecular forms present in desialylated AGP.