Immunoprecipitation of cell surface structures of cloned cytotoxic T lymphocytes by clone-specific antisera

Expression of structurally diverse Qa-2-encoded molecules on the surface of cloned cytotoxic T lymphocytes

Extracts of 125I-labeled cloned murine cytotoxic T lymphocytes (CTL) were immunoprecipitated with alloantisera to the cloned CTL and rabbit antisera to beta-2 microglobulin. Polyacrylamide gel electrophoresis (PAGE) of the specific precipitates revealed, as expected, 125I-labeled components that corresponded to products of class I genes of the major histocompatibility complex (MHC). However, additional class I gene products of relatively low apparent molecular weight (Mr) were also observed. Similar analyses of spleen cells from a variety of MHC-congenic mouse strains suggested that the class I molecules of relatively low Mr are encoded in the Qa-2 region of the MHC, and this was confirmed by immunoprecipitation with a monoclonal antibody to Qa-2. Surprisingly, however, the cell surface Qa-2 molecules of different CTL clones differed in Mr, in isoelectric focusing (IEF) pattern, and in the number of distinguishable molecules expressed per clone: some clones seemed to express only a single Qa-2-encoded molecule while others expressed two distinct ones. Treatment of the immunoprecipitated Qa-2 with endoglycosidase F (Endo F) resulted in a decrease in Mr of approximately 5,000-6,000, corresponding to the expected loss of N-linked oligosaccharides, but the decrease did not eliminate structural variability among the clones. Structural diversity of the Qa-2-encoded molecules expressed on CTL could arise because CTL clones differ (a) in the particular Qa-2 genes they express, (b) in the way they splice Qa-2 gene transcripts or, perhaps, (c) in Endo F-resistant oligosaccharides on their Qa-2 molecules.

Complete primary structure of a heterodimeric T-cell receptor deduced from cDNA sequences

Two related, but distinct, cDNA clones have been isolated and sequenced from a functional murine cytotoxic T-lymphocyte clone. The genes corresponding to these cDNA are expressed and rearranged specifically in T cells and both have similarities to immunoglobulin variable and constant region genes. It is concluded that these genes code for the two subunits of the heterodimeric antigen receptor on the surface of the T cell; its complete deduced primary structure is presented.