IgE response and its regulation in allergic diseases.

The distinguishing feature of the allergic person is his or her elevation of serum IgE. This propensity to develop a sustained IgE response is determined genetically. The biologic effects of IgE are mediated via Fc receptors (Fc epsilon R) present on mast cells and basophils (Fc epsilon R type 1) and subpopulations of monocytes, macrophages, eosinophils, and platelets (Fc epsilon R type 2). Interaction of allergen with IgE on these cells results in receptor "bridging" and the release of histamine and other inflammatory mediators. Fc epsilon R type 2 on lymphocytes and monocytes are upregulated in atopic disease and may play a role in the allergic inflammatory reaction. The activation of B cells to synthesize IgE requires several stages (see Fig. 2). T cells play an important role in the regulation of IgE synthesis. In vitro activation of resting B cells to synthesize IgE requires direct cellular interaction with T cells or the presence of IL4 for activation. The latter effect is inhibited by alpha-interferon. Preactivated B cells are influenced in an isotype-specific manner by T-cell-derived IgE binding factors (IgE-BF), which may act as IgE-potentiating or IgE-suppressive factors, depending on their degree of glycosylation. The regulation of IgE synthesis is an important area of investigation. It provides us with an understanding of the basis of the human allergic response and ultimately may provide the basis for novel strategies in the treatment of allergic diseases.