NKG2A buffers NK cell function on individual NK cells and in KIR repertoires characterized by low-KIR expression. (A) The observed frequencies of NK cells coexpressing the indicated KIR with NKG2A are plotted against frequencies obtained by multiplying their individual expression frequency according to the product rule. A perfect fit to the product rule is shown as a gray line, representing a 1:1 relationship between the observed and expected frequencies. (B) (Left panel) The frequency of NKG2A expression on NK cells expressing one self- or nonself-KIR (KIR3DL2 excluded). Importantly, this analysis was restricted to NK cells expressing one single inhibitory KIR since NKG2A expression is less frequent on NK cells expressing multiple KIRs²¹  and those have a higher chance of expressing a self-KIR. (Right panel) Frequencies of NKG2A expression in individuals with 1 to 3 strong KIR ligands. (C) CD107a expression was monitored on NK cells expressing zero to 4 KIRs with and without NKG2A upon interaction with HLA class I–negative K562 cells. (D) Gates were set on CD107a⁺ cells to monitor the contribution of different subsets of cells to the total NK cell response in individuals with the 3 repertoires. The relative contribution of the indicated subsets to the overall NK cell response in the 3 types of KIR repertoires is shown.