Isolation and partial characterization of a 72,000-dalton glycoprotein (Tgp72) on human thymus and T cells: possible relationship to mouse Ly-1 antigens

Abstract

A xenoantiserum was raised in guinea pigs to a human T cell antigen (Tgp72) partially purified from cell membrane of T cell leukemia cells from a patient with chronic lymphosarcoma cell leukemia of T cell-type by using sequential chromatographic procedures. The antiserum reacted with all of human thymus and peripheral T cells as well as with a variety of cultured leukemic T cell lines, but not with B cells, granulocytes, and other cultured lymphoid cell lines, including normal B cell, Burkitt, myeloid, and non-T non-B cell lines. Immunoprecipitated material from 125I-labeled thymocyte, T cell, and T cell leukemia cell-surface glycoproteins by this antiserum was analyzed by SDS-polyacrylamide gel electrophoresis, which disclosed a single component with a m.w. of 72K (Tgp72). Further immunochemical data suggest that Tgp72 antigen on human thymus and T cells is an acidic glycoprotein composed of a single polypeptide rather than sulfhydryl-linked subunits, showing a marked electric charge heterogeneity in DEAE anion-exchange resin chromatography. This is further confirmed by the data obtained from 2-dimensional polyacrylamide gel electrophoresis, indicating that Tgp72 is a 72K m.w. glycoprotein with an isoelectric point ranging from 4 to 7. Because of its similarity in tissue distribution and immunochemical characteristics, Tgp72 on human thymus and T cells was assumed to be a human homologue of Ly-1 antigens in murine system.