Maintained tolerance of NK cells expressing inhibitory KIR for nonself HLA class I ligands. (A) Gating scheme for analysis of CD107a on NK-cell subsets expressing KIR2DL1, KIR2DL3, KIR3DL1, and/or NKG2A after stimulation with K562 cells. Double events, CD14⁺, CD3⁺, and dead cells were excluded. Boolean gating of CD56^dim NK cells with and without NKG2A and expressing combinations of KIRs and CD107a was performed by FlowJo software. (B) Shown are functional responses of CD56^dim NK cells expressing self or nonself KIRs with or without NKG2A in the donor before SCT, and in the recipient at the indicated time points during the immune reconstitution. Self and nonself KIR refers to the presence or absence, respectively, of the corresponding ligand in the host. Mean values of 6 donor-recipient pairs are shown. Error bars represent SEM.