Essential role of Ly49D⁺ NK cells in rejecting MHC⁺B7⁺ tumor cells. RAG-1(-/-)C57BL/6 mice were pretreated with either PBS or anti-Ly49D mAb. The MHC⁺B7⁺ tumor cells (5 × 10⁶/mouse) were injected subcutaneously. (A) Representative contour graphs depicting NK subsets in PBS- or anti-Ly49D mAb-treated mice, as analyzed at 4 weeks after tumor cell challenge. The lack of Ly49D⁺ NK cells was not due to a blockade of fluorescein isothiocyanate (FITC)-conjugated anti-Ly49D antibody, as no Ig⁺ NK cells were found in the RAG-1(-/-) mice (J.X.G., unpublished observations, 2002). (B) Composite data that show almost complete depletion of Ly49D⁺ cells in vivo, 5 mice per group. (C) Tumor incidence (top) and growth kinetics (bottom) of MHC⁺B7⁺ tumors in PBS- or anti-Ly49D mAb-treated mice. Data shown are means and SEM of tumor diameters.