Characterization of a 95 kDa human leucocyte sialoglycoprotein: its identity with CD43, gpL115, leukosialin and sialophorin.

A monoclonal antibody, MEM-59, was prepared, which recognizes a heavily sialylated glycoprotein antigen expressed on most human leucocytes, the apparent molecular mass of which is strongly dependent on the concentration of polyacrylamide gel used for SDS-PAGE. The antigen isolated on immobilized MEM-59 reacted in Western blotting with mAbs described previously by others as recognizing antigens of similar properties. These experiments indicate that the molecules called CD43, gpL115 (sialophorin) or leukosialin are identical and different from a 75-85-kDa glycoprotein of similarly broad tissue distribution (CDw44). Most of the anti-CD43 mAbs recognize sialic acid-dependent epitopes. None of the anti-CD43 mAbs tested stimulated proliferation of peripheral blood leucocytes in vitro.