The chemoattractant Trp-Lys-Tyr-Met-Val-D-Met activates eosinophils through the formyl peptide receptor and one of its homologues, formyl peptide receptor-like 1.

Whereas prokaryotes use L- and D-isomers of amino acids in their protein synthesis, eukaryotic proteins as a rule incorporate only L-isomers. Hence, D-isomers may constitute danger signals to the innate immune system. A D-methionine-containing peptide, Trp-Lys-Tyr-Met-Val-D-Met-NH(2) (WKYMVm), has been shown to be a stronger activator of neutrophils than f-Met-Leu-Phe. The aim of this study was to compare the responsiveness of eosinophils to WKYMVm with that of neutrophils. The peptide was found to induce chemotaxis and respiratory burst in eosinophils. However, it did not mobilize granule constituents, as evidenced by a lack of eosinophil cationic protein, eosinophil peroxidase, and interleukin-5 in the supernatants of stimulated eosinophils. In contrast, WKYMVm caused the release of complement receptor 3 from secretory vesicles in neutrophils. Different members of the formyl peptide receptor family were preferentially engaged by the peptide in the two classes of granulocytes: the formyl peptide receptor itself in eosinophils and formyl peptide receptor-like 1 in neutrophils.