Primary KIR3DL1⁺NK cells are inhibited by HLA-A*32 and HLA-A*24. PBMCs from 7 healthy Bw4⁺ donors expressing both KIR3DL1^high and KIR3DL1^low were incubated for 4 hours with rituximab and BLCL target cells expressing different HLA-A and HLA-B molecules as indicated, in the absence or presence of the anti-KIR3DL1 DX9 antibody. (A) CD107a expression on NK cells singly expressing KIR3DL1^high or KIR3DL1^low are depicted. Two-way ANOVA with multiple comparisons was used for statistical analysis with **P < .01, ***P < .001, and ****P < .0001. (B) Specific inhibition of KIR3DL1^high and KIR3DL1^low NK cells by the indicated HLA-A Bw4⁺ allotypes, expressed as a percent decrease in activation following addition of DX9. Two-way ANOVA with multiple comparisons was used to calculate the significance within the KIR3DL1^high (red asterisks) or KIR3DL1^low groups (blue asterisks). Comparisons were made between NK cells cultured with Bw6-BLCL (reference) vs either B*38/B*52-BLCL, A*24-BLCL, or A*32-BLCL, respectively, with *P < .05 and ****P < .0001. Comparisons between KIR3DL1^high and 3DL1^low NK cells within each group are also shown (P = ns [not significant]).