The inhibitory effect of the Slam locus is mediated by 2B4 with no appreciable impact from other SLAM receptors or Gm10521. (A–D) Natural cytotoxicity of IL-2–expanded NK cells from wild-type, SFR KO, 2B4 KO, SLAMF7 KO (C57BL/6 background; A), CD84 KO (C57BL/6 background; B), SLAMF6 KO (C57BL/6 background; C), or Ly-9 KO (129S1/Sv background; D) mice was analyzed toward activated CD4+ T cells from either wild-type or SFR KO mice as targets, as detailed for Fig. 3 A. Results are representative of three (A), two (B and D), or four (C) experiments. (E) Natural cytotoxicity of IL-2–expanded NK cells from wild-type mice (C57BL/6) was tested against activated CD4+ T cells from wild-type, CD48 KO, Ly-9 KO, or SLAMF6 KO mice (129S1/Sv background), as detailed for Fig. 3 A. Results are representative of four experiments. (F) Natural cytotoxicity of IL-2–expanded NK cells from wild-type mice in C57BL/6, 129S1/Sv, or DBA/1J background was determined using activated CD4+ T cells from wild-type or CD48 KO mice as targets, as detailed for Fig. 3 A. Results are representative of three experiments. (G–I) Natural cytotoxicity of IL-15–expanded NK cells from either wild-type or 2B4 KO mice was analyzed against activated CD4+ T cells from wild-type, CD84 KO, SLAMF6 KO, Ly-9 KO, CD48 KO, or SLAMF7 KO mice, as detailed for Fig. 3 A. Results are representative of four (G), three (H), or two (I) experiments. (J and K) Natural cytotoxicity of IL-2–expanded NK cells from either wild-type or Gm10521 KO mice was tested at the indicated E/T ratio toward RMA, RMA-S, YAC-1, wild-type CD4+ T cells, and SFR KO CD4+ T cells. Results are representative of two experiments. Mean values of duplicates with standard deviations are depicted.