Functional analysis of HLA-specific receptors expressed on 3 different groups of KIR2DS1⁺ NK-cell clones. (A) 3 different groups of KIR2DS1⁺ NK cells clones (derived from the C1/C1 Bw4/Bw4 donor P61) characterized by the coexpression of NKG2A, KIR3DL1 or KIR2DL2/L3, were analyzed in a redirected killing assay against P815 cell line in the absence (white bars) or in the presence of 11PB6 mAb specific for KIR2DS1/L1 (black bars) or in the presence of mAb specific for the indicated HLA-specific inhibitory receptor (gray bars). The E:T ratio used was 4:1. Average of 3 independent experiments and SD (mean ± SD) are indicated. (B) Comparison between the cytolytic activity of KIR2DS1⁺NKG2A⁺ and KIR2DS1⁻NKG2A⁺ NK-cell clones derived from the same donor against untransfected, Cw4- or Cw6-transfected 221 cell line in the absence or in the presence of mAb to the indicated molecules. The E:T ratio used was 4:1. Average of 4 independent experiments and SD (mean ± SD) are indicated.