SURFACE GLYCOPROTEIN OF HUMAN NATURAL-KILLER-CELLS RECOGNIZED BY WHEAT-GERM-AGGLUTININ

We analyzed surface glycoproteins of human natural killer (NK) cells by utilizing lectins. Among the lectins tested, wheat germ agglutinin (WGA) was found to bind preferentially to CD16(Leu11)-positive lymphocytes as determined by two-colour flow cytometry. Analysis of glycoproteins in the lysate prepared from NK cells with sodium dodecyl sulfate (SDS) gel electrophoresis followed by Western blotting and I-125 labeled WGA staining revealed that a glycoprotein with an M(r) of 65 kDa was strongly bound to the lectin, but no corresponding glycoprotein was detected in the lysate of T lymphocytes. This glycoprotein (GP65) gave several spots in the pI range 4.1-4.6 on 2-dimensional gel electrophoresis. Sialidase treatment of GP65 resulted in a single spot on the 2-dimensional gel, suggesting that GP65 is heterogeneous in the degree of sialylation. GP65 was shown to be exposed on the cell surface, since it was radiolabeled with I-125 by the lactoperoxidase-catalyzed method. We next isolated GP65 from human peripheral blood lymphocytes by a combination of chromatography on a cation-exchange column and a WGA-agarose column and preparative SDS gel electrophoresis. It is suggested that GP65 is a novel surface glycoprotein on human NK cells.