A, C. IFN-γ response by KHYG-1 overexpressing KIR2DL4 (A) or primary NK cells from a 10A donor (C) that were stimulated overnight with plate-bound anti-KIR2DL4 mAb (clones 53.1, 33 or R&D 181703) or control mAb (2B4; Ctr.). IFN-γ in culture supernatant was assayed by ELISA. Insert dot-plot panels show FACS analysis of KIR2DL4 expression performed by combined staining with APC-conjugated anti-KIR2DL4 mAb (clone 33) and PE-conjugated anti-CD56a mAb (clone HCD56). B, D. KHYG-1 or Primary NK cell activation by plate-bound mAbs in the presence of various concentrations of soluble HS or CS (1, 5 and 25 μg/ml accordingly) as compared to PBS alone (NTC). NK cells were KHYG-1 (B) or Primary NK (pNK) (D); Insert panels show ELISA analysis of NK cell activation by plate-bound control mAb (2B4) in the presence of maximal concentration of soluble HS or PBS (NTC); IFN-γ in culture supernatant was assayed by ELISA. Data represent mean ((A) and (C)) ± s.d. and normalized to NTC mean ((B),(D) and inserts) ± s.d of n=3 independent experiments. P-values were calculated using T-Test (B): *p-value ≤ 0.03; **p-value and ***p-value ≤ 0.001; (D): *p-value ≤ 0.1; **p-value and ***p-value ≤ 0.008; P-values of NTC vs. CS are > 0.5 for both KHYG and pNK (all concentrations).