Does parasitic infection protect against allergy?

Immunoglobulin E (IgE) plays a central role in the pathogenesis of immediate hypersensitivity reactions because of its capacity to bind specifically to high-affinity IgE receptors on mast cells or basophiles by the alpha chain of Fc epsilon receptor type I (Fc-epsilon RI-α).1 In addition to its ability to activate mast calls and basophiles, IgE can bind to the low-affinity IgE receptor (CD23, or Fcepsilon RII) on B cells to augment cellular and humoral immune responses in allergic disease.2 Moderate to highly elevated IgE concentrations have been linked to IgE-mediated allergic disease, especially food allergy and one of its main manifestat ions, atopic dermatit is. In newborns and asymptomatic young infants, elevated IgE concentrations are an indicator of the likelihood of the development of allergic disease and they are a prognostic indicator in adults with certain types of chronic al lergic diseases. Serum IgE concentrations are highly variable, however when IgE levels are compared between allergic and non-allergic individuals, the average IgE concentration of the allergic individuals is almost always higher than that of the nonallergic individuals. Recent data suggest that mast cells can contribute to eosinophil-mediated inflammatory responses. Activation of mast cells can occur by antigen and immunoglobulin E via the liberation of proteases, leukotrienes, lipid mediators, and histamine contributing to tissue inflammation and allowing recruitment of eosinophils to tissue.