HLA-B*1302 and HLA-B*1301 do not inhibit cytotoxicity of KIR3DL1-dependent NK cells. (A) Polyclonally expanded NK cells from donor 1 were incubated with the class I HLA–negative cell line, 721.221 (positive control), a Bw6 control (B8; Table 2), a Bw4 control (B27; Table 2), 2 HLA-B*1302 targets, 1 HLA-B*1301 target, and 3 HLA-B*5101 targets. (B) CD107a expression was measured on KIR3DL1⁺, CD158b⁻ NK cells incubated with various target cells or alone (NA). CD107a expression was induced by the 721.221 cell line and the Bw6 control (B8), and not by the Bw4 control (B27) as expected. All targets expressing either HLA-B*1302 or HLA-B*1301 failed to inhibit CD107a expression. HLA-B*5101–expressing targets inhibited CD107a expression. (C) A total of 2 KIR3DL1⁺ NK clones (clone C3 from donor 4 expressing the low-expression KIR3DL1*005 allele and clone D2 from donor 3 expressing the high-expression KIR3DL1*01502 allele) were used in the 4-hour ⁵¹Cr release assay against the class I–negative cell line (721.221), a Bw6 control (B35; Table 2), a Bw4 control (B57; Table 2) and 2 HLA-B*1302 homozygous targets (panel A) to confirm lack of inhibition through KIR3DL1. KIR3DL1 was blocked with anti-DX9 (KIR3DL1; □) and isotype control (IgG₁; ■). Both NK clones lysed 721.221 and the Bw6 control (B35). Both NK clones were inhibited by the Bw4 control (B57), and inhibition was reversed in the presence of anti-KIR3DL1 mAb. Neither clone was inhibited by either HLA-B*1302 target with very little or no reversal of inhibition in the presence of the anti-KIR3DL1 mAb. Error bars represent SEM.