KIR2DS1⁺KIR2DL1⁻ NK cells from HLA-C2 homozygous donors are fully responsive to antibody-mediated cross-linking of KIR2DS1. (A) Example of KIR2DS1 and KIR2DL1 expression and degranulation measured by CD107a cell surface after coculture with P815 cells and anti-KIR2DL1/S1 mAb (clone 11PB6). The cells were stained with anti-KIR2DL1-FITC and anti-KIR2DL1/S1-APC (clone EB6) before stimulation to verify that only KIR2DS1⁺KIR2DL1⁻ NK cells responded above background to stimulation with 11PB6. (B) Summary of responses to cross-linking with 11PB6, normalized to the frequency of KIR2DS1⁺KIR2DL1⁻ NK cells in each of the donors.