NKp30 and NKp44 mediate tumor cell killing by NCR⁺ γδ PBLs. (A) Functional evaluation of NKp30, NKp44 and NKp46 using specific monoclonal antibodies in a 4-hour ⁵¹Cr release redirected killing assay (at 2:1 effector:target ratio) of the FcγR⁺ P815 target cell line by γδ PBLs activated and expanded with PHA and IL-2. Data are presented as mean and SD of 8 independent experiments performed in triplicate (*P < .05, ***P < .001; ns = not statistically significant). (B) γδ PBLs activated and expanded for 18 days in PHA and IL-2 were incubated (at 5:1 effector:target ratio) for 3 hours with the leukemia cell line MOLT-4 (as in Figure 1). Effect of blocking antibodies to NKp30, NKp44, NKp46 and TCRγδ (IMMU510) on tumor cell killing. (C) Vδ1⁺ PBLs were MACS-sorted after 20 days in PHA and IL-2 cultures for the assay described in (B), but using blocking antibodies to pan-TCRγδ (IMMU510 and B1.1), Vδ1⁺ TCR (TCS1), NKG2D or NKp30 and NKp44, or the depicted combinations. (+) refers to control cultures without inhibitory antibodies; (-) refers to tumor cell cultures without Vδ1⁺ PBLs. Error bars represent SD (n = 3, *P < .05; **P < .01; ***P < .001).