The chicken erythrocyte-specific MHC antigen. Characterization and purification of the B-G antigen by monoclonal antibodies.
Mouse monoclonal antibodies with B-G antigen (major histocompatibility complex class IV) specificity were obtained after immunization with erythrocytes or partially purified B-G antigen. The specificities of the hybridoma antibodies were determined by precipitation of B-G antigens from 125I-labeled chicken erythrocyte membranes (CEM) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. The B-G antigen had an approximate molecular mass of 46-48 kd in reduced samples, depending on the haplotype, and in unreduced samples contained either dimers (85 kd), when labeled erythrocytes were the antigen source, or trimers (130 kd), when B-G was purified and precipitated from CEM. The B-G antigen was unglycosylated as studied by in vitro synthesis in the presence or absence of tunicamycin, binding experiments with lectin from Phaseolus limensis, and treatment of purified B-G antigen with Endoglycosidase-F or trifluoromethanesulfonic acid. Two-way sequential immunoprecipitation studies of erythrocyte membrane extracts with anti-B-G alloantisera and monoclonal antibodies revealed only one population of B-G molecules. Pulse-chase experiments have shown B-G to be synthesized as a monomer, with dimerization taking place after 20-30 min. No change in the monomer's molecular mass due to posttranslational modifications was revealed. The antigen was purified from detergent extract of CEM by affinity chromatography with a monoclonal antibody, and then reduced and alkylated and affinity-purified once more. Finally, reverse-phase chromatography resulted in a pure product. The B-G antigen was identified in the various fractions by rocket immunoelectrophoresis. The final product was more than 99% pure, as estimated by SDS-PAGE analysis followed by silver stain of proteins. The yield from the affinity chromatography step was 3-4 micrograms B-G/ml blood, calculated from Coomassie-stained SDS-PAGE of B-G using ovalbumin standards. The monoclonal antibodies were also used to identify the B-G (class IV) precipitation arc in crossed immunoelectrophoresis. No common precipitate with the B-F (class I) antigen was observed.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D002241:Carbohydrates / Q000032:analysis; D002645:Chickens / Q000097:blood / Q000276:immunology*; D002846:Chromatography, Affinity; D000939:Epitopes / Q000276:immunology; D004912:Erythrocytes / Q000276:immunology*; D006649:Histocompatibility Antigens / Q000096:biosynthesis / Q000276:immunology / Q000302:isolation & purification*; D007123:Immunoelectrophoresis, Two-Dimensional; D008285:Major Histocompatibility Complex; D008970:Molecular Weight
D000911:Antibodies, Monoclonal; D002241:Carbohydrates; D000939:Epitopes; D006649:Histocompatibility Antigens