KIR2DS1 does not affect NK-cell alloreactivity against AML cells. 1265 NK-cell clones from 10 HLA-C1⁺ individuals were screened for cytotoxicity against a panel of 4 HLA-C1–missing, HLA-C2/C2 AML (A-D). The contribution of KIR2DS1 to lysis was evaluated in 59 allocytotoxic NK-cell clones that expressed KIR2DL2/L3 (as evaluated by phenotypic analyses). Lysis (mean ± SD) exerted by KIR2DS1^– (squares) and KIR2DS1⁺ alloreactive NK-cell clones (triangles) is shown. (A) Lysis by 19 alloreactive NK-cell clones of 270 clones obtained from 2 individuals. (B) Lysis by 14 alloreactive NK-cell clones of 224 clones obtained from 2 individuals. (C) Lysis by 11 alloreactive NK-cell clones of 258 clones obtained from 3 individuals. (D) Lysis by 15 alloreactive NK-cell clones of 479 clones obtained from 3 individuals.