IgE-dependent release of myeloperoxidase by neutrophils from allergic patients

Background The three forms of IgE receptor: the heterotrimeric high-affinit y receptor for IgE (Fc epsilon RI), the low-affinity receptor for IgE (Fc e psilon RII/CD23) and the Mac-2/IgE-binding protein (epsilon BP), have previ ously been found on human neutrophils. We have previously shown that specif ic allergens are able to activate functional responses by neutrophils from allergic patients sensitized to those allergens. Neutrophils are present in the sites of allergic inflammation. The primary (azurophilic) granules of neutrophils contain a variety of enzymes that might potentiate inflammation , such as myeloperoxidase (MPO). It is not known whether specific allergens are able to elicit MPO release by neutrophils from allergic patients. Methods Neutrophils were challenged in vitro with the specific allergen tha t produced clinical symptoms in asthmatic patients. Also, the cells were ch allenged with allergens that the patients were not sensitive to. Neutrophil s from normal subjects were also challenged with allergens. Results The in vitro challenge of neutrophils with allergens that the patie nts were sensitive to elicited a release of MPO by these cells. The in vitr o activation of neutrophils was highly allergen-specific, in such a way tha t allergens other than those accounting for clinical symptoms did not evoke MPO release, and allergens were ineffective on neutrophils from healthy do nors. Conclusion An IgE-dependent mechanism might promote MPO release by neutroph ils at allergic sites.