Figure 4.

FcγR-cross-linking induces activation of TAK1. Human neutrophils were left untreated (---), or (A) were stimulated with 5 ng/ml transforming growth factor-β (TGF-β), or by cross-linking FcγRIIIb for 15 min. (B) neutrophils were also stimulated with 20 nM phorbol 12-myristate 13-acetate (PMA), or by cross-linking FcγRIIIb (FcR) for 5, 15, and 30 min. (C) neutrophils were also stimulated by cross-linking FcγRI with mAb 32.2, by cross-linking FcγRIIa with mAb IV.3, or by cross-linking FcγRIIIb with mAb 3G8 for 15 min. Cell lysates were prepared after stimulation. Proteins were resolved by SDS-PAGE, and then Western blotted for phosphorylated-TAK1 (pTAK1) (upper panel) or for total ERK (lower panel). Data are representative of three separate experiments.