Anti-IgE autoantibodies in asthma: a diagnostic artefact or an explanation for non-allergic asthma?

: Autoantibodies to IgE can be detected in sera of individuals with atopic disease, but occasionally elevated levels are also found in sera of normal individuals. During the last years we studied therefore the functional properties of such autoantibodies. Depending on the studied in vitro system one can always detect minimally two different antibody types. Antibodies have been found that either trigger or inhibit mediator release from basophils, that enhance or inhibit binding of IgE to the low IgE receptor and either stimulate or inhibit human IgE synthesis. Based on such in vitro experiments one may conclude that also in vivo autoantibodies exist that either neutralize IgE or have no effect on IgE mediated clinical events. Thus, anti-IgE autoantibodies may hide IgE as for example in those bee sting allergic individuals where we could not detect specific IgE but found IgE hidden within immune complexes, suggesting that the biological activity of IgE was not neutralized. A similar phenomenon may exist in asthmatic individuals. In a recent study we found that non-atopic asthmatic children had indeed low levels of serum IgE, but showed the same levels of autoantibodies to IgE, against suggesting that IgE was hidden within immune complexes. Thus, our ongoing research addresses the question whether in diseases of unclear atopic origin IgE may nevertheless play a critical role but based on possible artefacts in the IgE detection assays some of the clinically relevant IgE may escape.