Activating receptor–mediated NK cell apoptosis is cyclosporin A sensitive.

(A) The NK cell clone 45 (CD94⁺ activating; ▴) or the NK cell clone 12 (p50.3⁺ activating; ▪) was incubated with their specific sHLA ligands (sHLA non-A, -B, -C, and -G [that is, HLA-E and HLA-F] for CD94/NKG2 complex or sHLA-Cw3 for p50.3) either alone (0 ng/mL CsA; left symbols in panel A) or with increasing doses of cyclosporin A (5, 50, 500 ng/mL) for 48 hours, and apoptosis was evaluated by FITC–annexin V labeling. Results are expressed as the percentage of maximal apoptosis. Maximal apoptosis was 85% for NK cell clone 45 and 78% for NK cell clone 12, respectively. ♦ indicates percentage of maximal apoptosis of the NK cell clone 45 incubated for 48 hours in medium alone. (B) Amount of sFasL present in culture supernatant recovered after 24 hours of incubation under the experimental conditions described in panel A with the same NK cell clones. Results are expressed as nanograms per milliliter as determined by ELISA. (C) Concanamycin A does not affect activating receptor–mediated apoptosis. The NK cell clone 12 (p50.3⁺activating) was incubated with sHLA-Cw3 or GAM-coated beads (4 per cell) after staining with anti-p50 mAb (1 μg/mL) (p50.3-XL) for 48 hours in the presence or absence of 3 μg/mL concanamycin A or with 500 ng/mL CsA and stained with FITC–annexin V. “nil” indicates apoptosis in medium alone. Results are expressed as the percentage of apoptotic cells (FITC–annexin V⁺ but PI⁻) and are representative of 3 independent experiments.