Figure 6.

Cross-desensitization between CXCR and the formyl peptide receptor (FPR). Neutrophils (1 × 10⁶/ml), activated by (and subsequently desensitized to) f-Met-Leu-Phe (fMLF) (10 nm), were challenged with interleukin-8 (IL-8) (12·5 nm); the formyl peptide was added to the cells at time 0 and IL-8 was added 5 min later (dotted line). In parallel, neutrophils (1 × 10⁶/ml) activated by (and subsequently desensitized to) IL-8 (12·5 nm), were challenged with fMLF (10 nm); IL-8 was added to the cells at time 0 and fMLF was added 5 min later (solid line). The release of superoxide anion was determined during a 10-min period following addition of the initial stimulus, and the curves are from a representative experiment. CL, chemiluminescence; c.p.m., counts per minute.