Agonist‐induced lipoxin A 4 generation: Detection by a novel lipoxin A 4 ‐ELISA

Lipoxin A 4 (LXA 4 ) possesses potent bioactions. To facilitate its detection, an enzyme‐linked immunosorbent assay (ELISA) was developed that proved sensitive and selective. Quantitation by ELISA of LXA 4 generated from cellular sources strongly correlated (r=0.99) with values obtained by high‐pressure liquid chromatography (HPLC). We used this LXA 4 ‐ELISA to examine parameters influencing LXA 4 generation from endogenous substrates during human platelet‐neutrophil (PLT‐PMN) interactions in vitro . Agonist‐induced LXA 4 production was clearly evident at a PLT‐PMN ratio of 10∶1, and recombinant human granulocyte/monocyte colony stimulating factor‐priming of PMN augmented LXA 4 generation 5–6 fold. The chemotactic peptide formylmethionyl‐leucyl‐phenylalanine, platelet‐derived growth factor and arachidonic acid (20∶4n−6) each stimulated formation of immunoreactive LXA 4 (iLXA 4 ) in these co‐incubations. The presence of iLXA 4 was also evaluated in vivo in aspirin‐sensitive asthmatic patients who, in a randomized, double‐blind crossover design, underwent nasal lavage after they each ingested a predetermined threshold dose of aspirin or placebo. Aspirin challenge provoked statistically significant increases in iLXA 4 in each patient ( P <0.005). These results validate the use of a solid‐phase ELISA for detection of LXA 4 . Furthermore, the use of this ELISA has allowed the first documentation of iLXA 4 formation in human subjects with aspirin‐sensitive asthma following specific antigenic challenge.