The role of IgG1 and IgG4 as dominant IgE-blocking antibodies during allergen immunotherapy

Allergen immunotherapy (AIT) is the only treatment that modifies the allergic response to allergens. One immune mechanism associated with a reduction in clinical symptoms is the induction of immunoglobulin E (IgE)-blocking antibodies. In particular, AIT-induced allergen-specific IgG4 antibodies were regarded a candidate biomarker for clinical efficacy. With the knowledge that not all AIT-induced allergen-specific IgG antibodies bear blocking bioactivity, different in vitro assays became popular to assess the blocking capacity of sera collected during and after AIT. Their measuring principles vary in the detection of the prevention of IgE-binding to allergen or of allergen interactions with IgE bound to high-affinity Fc epsilon receptors on the surface of effector cells. More recently, the contribution to IgE-blocking of other isotypes that arise in the course of AIT, e.g., IgG1 and IgA, was confirmed. The results indicated that different isotypes of allergen-specific antibodies serve as dominant IgE-blocking factors in the course of AIT.