Limited trypsin cleavage distinguishes MHC and thymus-leukemia antigens

A simple technique is presented for the identification of particular cell membrane antigens. The method employs labeled membrane antigens that are isolated immunospecifically and subjected to limited trypsin digestion followed by polyacrylamide gel electrophoresis in detergent. A large "core" peptide is produced by proteolysis of murine thymus-leukemia antigens (TLA) and from antigens of the major histocompatibility complex (MHC). The tryptic cores from H-2K and H-2D are regularly distinguishable from the thymus-leukemia antigens (TLA) by gel electrophoresis in one dimension. This chemical distinction is particularly important in the analysis of antigen mixtures isolated with antisera specific for beta 2 microglobulin. These techniques have been used to identify thymus-restricted beta 2 microglobulin-associated antigens on cell membranes from mouse, man, guinea pig, and monkey. In appropriate inbred mouse strains, these are the TLA and it is proposed that in the three other species examined they may be analogues, although not necessarily homologues, of TLA. The broad species distribution of these thymus-restricted cell membrane antigens suggests that they are involved in the differentiation of thymus-dependent lymphocytes (T cells).