Selectivity of NK cell cross-tolerance induction. B6-derived NK cells were exposed to anti-Thy1 mAb (αThy1)–coated RMA cells to induce chronic ADCC (▴) (A) or exposed to MHC class I–deficient RMA/S cells (missing-self recognition, ♦) (B). Ly49D⁺ (■) and Ly49D- NK cells (□) were exposed to CHO cells (C). As controls, NK cells were exposed to RMA cells (○) or to RMA-H60 cells (•). After 3 days of coculture residual tumor cells were removed and the cytolytic activity of NK cells toward RMA H60, anti-Thy1 mAb (αThy1)–coated RMA, RMA/S, and CHO target cells was determined. The Ly49D-dependence of CHO lysis was ensured by blocking with anti-Ly49D mAb (). Error bars are SD.