Human neutrophils and monocytes produce anaphylactogenic mediators. (A-D) Purified human monocytes or neutrophils were incubated in vitro with heat-aggregated human IgG or anti-FcγRIIA mAb IV.3, and (A) CD62L expression, (B) PAF, (C) LTB₄, and (D) LTC₄ production are represented. Mean results from the analysis of 3 normal donors are represented (*P < .05; **P < .01; ***P < .001).