Target—effector interaction in the natural killer cell system: Isolation of target structures

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Abstract
A sensitive target binding assay detects natural killer (NK) cells in the mouse. Preincubation of NK cells with detergent-solubilized cell-surface proteins of YAC lymphoma cells prevented subsequent binding to intact YAC targets. The NK target structures (NK-TS) consisted of 3 molecular species tentatively assigned MW of 130,000, 160,000 and 240,000 based on electrophoretic mobility in sodium dodecyl sulfate/polyacrylamide gels. Moloney cell surface antigen (MCSA), gp71, p30, H-2 and NK-TS were localized in distinct fractions of gels. The NK-TS bound to concanavalin A-Sepharose columns and was eluted with the specific sugar, suggesting that the target structures may be glycosylated. NK-TS was not detected in gels of NK-insensitive target cells such as [mastocytoma] P815 [fibroblastic L cell], A9HT [Moloney leukemia virus-induced lymphoma], YWA, or [thymus-derived (T) cell lymphoma] EL-4. The quantity obtained from the gels varied directly with the NK sensitivity of YAC which is more sensitive when grown in vitro than when grown in vivo. The NK-TS molecules specifically inhibited the binding of NK cells but not alloimmune T cells to their appropriate targets. Additional NK-sensitive tumor cells expressed some or all of the target molecules exhibited by YAC. Some of these structures shared specificities in the case of [plasmacytoma] MPC-11 or were unique in the case of [human T cell leukemia] Molt-4 and [human myeloid leukemia] K562, as shown by cross-inhibition studies. NK-sensitive cell lines may express distinct target structures with possible relevance to natural tumor resistance.

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