The restriction to the manipulation of the immunoglobulin gene locus allows the dissection of B-cell versus T-cell contribution to the acute allergic phenotype. This new mouse strain allows active immunization experiments to sensitize for anaphylaxis induction. We believe this is closer to the dynamic in vivo situation in allergic patients where polyclonal or oligoclonal antibody responses of different antibody isotypes are induced.

The results presented here suggest that a strong antigen-specific polyclonal IgE response is most powerful in sensitizing both Ivacaftor solubility dmso basophils and mast cells. Nevertheless, basophil-depletion experiments indicate that antigen-specific Tipifarnib price IgE on basophils plays an important role in the anaphylactic process in vivo. This view is indirectly supported by recent data that an IgE-specific hypersensitivity inhibiting molecule called Allergin-1, is expressed on

mast cells but not basophils [9]. Mast cells, however, do contribute to the anaphylactic reaction in vivo, since a partial anaphylactic drop in body temperature occurs even in basophil-depleted mice. Our data are in partial contrast to results, which suggested that basophil-dependent passive systemic anaphylaxis is IgG1 mediated, but not IgE mediated [9, 37]. The probable reason for this difference is that passive sensitization with monoclonal IgE is less efficient, due to the instability of IgE, compared with a polyclonal IgE antibody response. Recently, Parvulin Sawaguchi et al. showed that in a passive systemic anaphylaxis model, mast cell but not basophil depletion inhibited anaphylaxis [38]. In addition, Ohnmacht et al. [40] demonstrated for the Mcpt8Cre-basophil-deficient mouse model that

in active systemic anaphylaxis no difference between controls and the basophil-lacking mice exist. This does not contradict our data, because in the IgEwt/wt mice, where IgG1 levels dominate IgE, basophil depletion has only a minimal suppressive effect on anaphylaxis. This supports the hypothesis that basophils are dispensable for an IgG1-dominated anaphylaxis reaction [39]. Studies with novel basophil- or mast cell-deleted mouse strains have to be performed in order to elucidate the precise contribution of basophils versus mast cells in IgE-mediated active anaphylaxis [39, 40]. Further support for our model comes from experiments, which suggest that IgG-containing immune complexes inhibit (via FcgRIIB) rather than activate (via FcgRIIIA) basophils. They also show an inhibitory effect of IgG on IgE-mediated basophil activation, suggesting that the lack of an inhibitory signal by IgG1 could contribute to the increased IgE-mediated anaphylaxis we observed in IgEki/ki mice [18, 21]. First, we used CD23−/− to avoid passive binding of IgE to B cells.