We previously clarified that serum IgA suppresses primary antibody response, in contrast to IgG, IgE and IgM which enhance the response. In this study, we investigated the competitive potential of immunosuppressive IgA to IgE-enhanced immune response. Sensitization of mice with anti-ovalbumin (OVA) monoclonal IgE OE-1 (Day -1) and challenge with OVA on the next day (Day 0) induced anaphylaxis (Day 0) and subsequent immune responses including primary antibody response (Day 11) and cytokine production from cultured, antigen re-stimulated splenocytes (Day 14). Anti-OVA IgA monoclonal antibody OA-4 administration before the OVA challenge did not inhibit the OE-1-induced anaphylaxis but inhibited the OE-1-enhanced immune responses, indicating that anaphylaxis and immune responses are independent each other. Importantly, OA-4 administration after the OVA challenge could also inhibit the OE-1-enhanced immune responses. These findings indicated that IgA administration after anaphylaxis in mice is effective to diminish the IgE-enhanced sensitization. The suppression of the boosting phase by IgA is considerable to be an effective treatment to ameliorate allergic diseases.

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