Preliminary structural characterization of the leukocyte cell surface molecule recognized by monoclonal antibody TA-1.

TA-1 is a monoclonal antibody identifying a cell surface molecule with a broad distribution on normal and malignant human leukocytes. Preliminary structural studies performed by using radioimmunoprecipitation and sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that TA-1 recognizes a two-chain polypeptide of approximately 170 kilodaltons (KD) and 95 KD under reducing conditions. The same experiment conducted under nonreducing conditions yielded bands of approximately 155 KD and 110 KD, suggesting the existence of intrachain disulfide bonds in both subunits. Both polypeptide chains were labeled with tritiated sodium borohydride after treatment of cells with neuraminidase and galactose oxidase, thereby demonstrating that both were glycosylated. Tryptic peptide mapping indicated that the 170-KD and 95-KD subunits did not have significant homology in peptide composition. We are designating this newly defined human leukocyte bimolecular complex gp 170/95.