Activation of human neutrophils by surface-associated IgA is associated with the release of activated collagenase

Neutrophils contain on their surface a receptor for the Fc portion of IgA. Cross-linking of this receptor in the fluid phase induces superoxide production and release of granule constituents, but the response to surface associated IgA has not been previously studied. Neutrophils incubated with surface-associated IgA (SAIgA) release significant amounts of activated collagenase in addition to the granule proteins myeloperoxidase and lactoferrin. This activation is associated with release of superoxide as well as hydrogen peroxide and hypochlorous acid. Although neutrophils incubated with soluble aggregates of IgA also release granule proteins and produce superoxide, soluble aggregates of IgA do not trigger the release of activated collagenase and do not generate hydrogen peroxide or hypochlorous acid. In summary, neutrophils activated by surface associated IgA respond differently than when cells are activated by soluble aggregates of IgA. These differences may be important in understanding the mechanisms of tissue injury in patients with inflammatory disorders.