Isolation and characterization of human B cell alloantigens

Abstract

Human B lymphocyte alloantigens were solubilized from malignant spleen cell membranes from lymphoma patients by detergent treatment or papain digestion. Antigenic activity was detected by inhibition of cytotoxicity of rabbit and human anti-B cell antisera. Extracts from one patient (AC) specifically inhibited only B alloantisera of B groups 1 and 3; sera from B groups 4 and 5 were not inhibited. Inhibitory titers were greater than 1:400 against positive sera and less than 1:2 against negative sera. The papain extracts were purified by QAE-A50 Sephadex and Concanavalin A Sepharose 4B chromatography, and preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis (PAGE) under nondenaturing conditions. By testing gel slices for antigenic activity the m.w. of the papain-extracted B antigen was 58,000 whereas the detergent-extracted antigen was 65,000. Antigenic activity detected by rabbit and human antisera copurify together, suggesting that these sera were reacting with the same molecules. Immunoprecipitation of sodium deoxycholate-solubilized extracts of a cultured human B lymphoid cell line 8392 with the rabbit anti-B cell antisera revealed two B cell polypeptides of apparent m.w. 27,000 and 35,000 that were not found on the paired T line 8402. It is suggested that these polypeptides might be subunits of the 65,000 dalton native B lymphocyte alloantigen. The polypeptide subunits do not appear to be linked covalently by disulfide bonds.