Recognition of asparagine-linked oligosaccharides on murine tumor cells by natural killer cells

Abstract

MDW4, a wheat germ agglutinin resistant mutant of the murine tumor line MDAY-D2, expresses abnormal asparagine-linked oligosaccharides, is less metastatic when injected intravenously, and is hypersensitive to natural killer (NK) lysis in vitro. To determine whether these phenotypes may be related, variants of the YAC-1 lymphoma and a YAC-1 X MDAY-D2 hybrid line were compared for sensitivity to four different lectins and to NK cell lysis in vitro. A relationship between sensitivity to concanavalin A (Con A) and NK cell lysis in vitro was observed. Although no single plasma membrane glycoprotein separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with 125I-labeled Con A correlated with NK and Con A sensitivities of the cell lines, a relationship between these phenotypes and the collective 125I-Con A staining intensity on the gels was apparent. In a more direct test of carbohydrate recognition by NK cells, specific glycopeptide structures isolated from tumor cells and added to the NK cell assay in microM quantities were found to inhibit tumor cell lysis. Thus, a subset of asparagine-linked oligosaccharides, including high mannose and some incomplete complex structures on a number of cell surface glycoproteins, appears to be recognized as part of the target structures for NK cell lysis. The administration of polyinosinic:polycytidylic acid stimulated splenic NK activity in vivo but had no effect on the growth of the NK-resistant MDAY-D2 cells. However, the low tumorigenicity of MDW4 cells injected intravenously was reduced further by pretreating the mice with polyinosinic:polycytidylic acid, which indicated a role for NK cells in the elimination of circulating tumor cells expressing high mannose and/or incomplete complex asparagine-linked oligosaccharides.