Increased specific immunoglobulin G4 antibodies induced by natural exposure to ambrosia pollen in patients with allergy

Background: Induction of specific immunoglobulin G4 (sIgG4) response (so-called blocking antibodies) in patients who receive specific immunotherapy (SIT) has been observed for many years. Although many other mechanisms have been identified as key regulators of immunologic processes in peripheral tolerance to allergens, the rise of sIgG4 during immunotherapy, together with the clinical improvement, is still believed to be one of the most important mechanisms through which SIT reaches its clinical efficacy. Objective: The aim of this prospective study was to measure levels of IgG4 and sIgE in subjects allergic to Ambrosia elatior pollen (common ragweed), before and during natural exposure to A. elatior pollen. Healthy controls were also included. Methods: Twenty-four patients with allergic diseases of the respiratory tract and 24 healthy controls entered the study. The sIgG4 and sIgE levels were measured by using the enzyme-linked immunosorbent assay method before and during A. elatior pollination season. Results: A significant increase of the sIgG4 level in subjects with allergy during natural exposure to an allergen (0.676 increased to 0.937; p < 0.05) was shown. An increase in sIgE levels was also observed. Healthy subjects had comparable levels of sIgG4 as in subjects with allergy before the pollination season and no change in sIgG4 and sIgE levels during the pollination season. Conclusion: Increases of sIgG4 and sIgE levels were induced by natural allergen exposure in subjects with allergy but not in healthy individuals. This result support further reevaluation of the "blocking" antibodies concept as one concept responsible for allergen tolerance in patients who receive SIT.