Antigen-specific IgG and IgA, but not IgE, activate the effector functions of eosinophils in the presence of antigen.

BACKGROUND

Activated eosinophils are thought to play an important role in allergic inflammation. Prior reports suggest that eosinophils have receptors recognizing IgA, IgG and IgE; however, little is known regarding the direct effects of antigens and antigen-specific immunoglobulins on the functions of eosinophils.

METHODS

To investigate eosinophil activation by antigens mediated by the various antigen-specific immunoglobulins, we used dansyl-conjugated bovine serum albumin (DNS-BSA) and recombinant dansyl-specific antibodies (human IgG 1-4, IgA and IgE). Eosinophils from healthy donors were incubated in the wells coated with dansyl-specific immunoglobulins with or without DNS-BSA. Eosinophil activation was monitored by superoxide production and eosinophil-derived neurotoxin (EDN) release.

RESULTS

Superoxide production and EDN release by eosinophils were induced by the dansyl-specific reaction via all IgG subclasses (IgG 1-4) and IgA in the presence of DNS-BSA; the responses were not observed in the absence of antigen, DNS-BSA. The immune complexes (ICs) of DNS-BSA and dansyl-specific IgE did not induce these responses. Furthermore, IgE ICs did not enhance eosinophil activation stimulated with various immunoglobulins, IL-5 or platelet-activating factor.

CONCLUSION

These data suggest that ICs of antigens and antigen-specific IgGs and IgA, but not IgE, in inflamed tissues may activate eosinophils and play an important role in allergic inflammation.