Preparation of photocaged HLA-Cw3. (A) Photocaged Ser was synthesized and incorporated into the importin-α peptide, which was then refolded with purified HLA-Cw3 and β2m. UV irradiation of HLA-Cw3(cage) yields stimulatory HLA-Cw3(Ser). (B and C) IFN-γ secretion (B) and degranulation (C) of KIR2DL2-expressing NKL cells stimulated on plastic surfaces coated with the indicated activating and inhibitory molecules. HLA-Cw3(cage) was either UV irradiated or left untreated before immobilization on the stimulatory surfaces. Asterisks in B denote P < 0.001 (Student’s t test). Unstim, unstimulated. Error bars show SEM between replicates, with n = 3. Data are representative of at least three independent experiments.