Molecular identification of T cell‐specific antigens on human T lymphocytes and thymocytes

We have identified membrane glycoproteins which carry T cell-specific antigens on human T lymphocytes and thymocytes. Purified cells were surface-labeled with NaB3H4 after treatment with neuraminidase and galactose oxidase. Immunoprecipitations were performed with rabbit anti-human T cell-specific antibodies using coprecipitation with protein A-containing staphylococci strain Cowan I. The labeled membrane glycoproteins and the precipitates were subjected to polyacrylamide slab gel electrophoresis and visualized by fluorography. The antibodies specifically precipitated 4 proteins called GP 200, GP 180, GP 165 and GP 160 (mol. wts. = 200,000, 180,000, 165,000 and 160,000) from surface-labeled T lymphocytes and low-density (medullary) thymocytes. The GP 200 and GP 180 were not labeled on high-density (cortical) thymocytes. A protein with a mol. wt. of 45,000 was precipitated from thymocytes. Another glycoprotein on T lymphocytes and thymocytes with a mol. wt. similar to that of mouse and rat Thy-1 or theta antigen (mol. wt. 24,000) reacted with the antibodies.