Education promotes amplification and skewing of the KIR repertoire. (A) NK cells were labeled with CFSE and were cultured for 7 or 14 days with IL-15 alone or together with irradiated 221.wt or 221.AEH cells. At day 7 or day 14, cells were assessed for KIR and NKG2A/C expression. (B-D) Size of the NKG2C⁺ subset and KIR expression at day 0 and day 14 in coculture experiments with 221.AEH cells. Shown are representative examples (top) and pie charts (bottom) of NKG2C⁺ NK cell amplification and KIR skewing in (B) a CMV-seropositive donors without preexisting expansion, (C) a CMV-seropositive donor with preexisting expansion, and (D) 2 CMV-seronegative donors (C2/C2 left and C1/C1 right).