Mac-1 is crucial for FcR-mediated PMN cytotoxicity of tumor targets.

(A) Lysis of human breast carcinoma (SK-BR-3) cells mediated by Tg Mac-1^+/− PMNs (▪) and Tg Mac-1^−/− PMNs (░) in the absence (control) or presence of FcαRI-directed BsAb [A77 × 520C9]. Cytotoxicity was analyzed after 4 hours at different E/T ratios (20:1 and 80:1). Results are presented as mean ± SEM (n = 6), (*P < .0001). (B) FcαRI-mediated cytotoxicity toward SK-BR-3 cells by human PMNs (E/T ratio; 50:1) in the absence (control) or presence of BsAb [A77 × 520C9]. The effect of anti–Mac-1 mAb 44a or M1/70, and NADG on ADCC was analyzed as described in “Materials and methods.” Data are presented as mean ± SEM (n = 3). *Significant difference compared with BsAb alone (P < .002).