Mast cells release CXCR2-binding neutrophil chemoattractants. (A) Time course of CXCL1 and CXCL2 ± CHX synthesis by purified mast cells; mean ± SEM of 4 experiments. (B) Time course of CXCL1 and CXCL2 synthesis by purified WT and TLR4^−/− mast cells; mean ± SEM of 2 experiments. (C) Supernatants from purified mast cells stimulated with PBS (MC + PBS) or LPS (MC + LPS) for 4 hours tested for neutrophil chemoattractant activity and compared with recombinant CXCL1. Neutrophils were preincubated with anti-CXCR2 or control IgG2a mAbs; mean ± SEM of 3 experiments is shown.