Human homologue of the murine T-200 glycoprotein

One approach to understanding the molecular basis of the cellular interactions that take place during the immune response is to identify and characterize the cell-surface glycoproteins of the cell types involved to identify molecules that may play a role in these processes. In man, cell-surface glycoproteins of thymus-dependent (T) and thymus-independent (B) lymphocytes and lymphoblastoid cell lines have previously been analyzed by a combination of various surface-labeling techniques, immunopre-cipitation with conventional xenoantisera, nd analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) t (1-3). Comparison of the surface proteins of HSB2, a human T leukemic ell line, and CCRF-SB, a normal B cell line from the same patient, by these methods, revealed characteristic differences in their high molecular weight surface molecules: the B cell line expressed a molecule with an apparent molecular weight of ~220,000, whereas HSB2 cells expressed a molecule with an apparent molecular weight of 200,000 (1). Similar differences in the high molecular weight glycoproteins of normal human T and B lymphocytes have also been reported (2, 3). Recently, the monoclonal antibody technique (4) has greatly facilitated the analysis of surface molecules of human lymphoid cells (5). With this technology, we report here data that demonstrate he differences between the high molecular weight surface molecules of human T and B cells can be accounted by the presence of structurally distinct but antigenically related glycoproteins on their cell surface. Chemical char-acterization, including two-dimensional peptide mapping, shows that these glycopro-teins are the human homologues of murine T200 glycoprotein (6, 7)