Polyisotypic antipeanut-specific humoral responses in peanut-allergic individuals

Background Peanut-containing food products may induce severe clinical react ions in sensitized subjects, and high levels of antipeanut IgE have been re ported in the literature. Immunotherapy, proposed for the prevention of sev ere accidents, is often ill-tolerated and only partly efficient. This could be due to the spontaneous development of polyisotypic antipeanut antibodie s. Objective To appreciate the presence and reactivity of other isotypes other than IgE of peanut-specific antibodies in serum samples from peanut-sensit ized subjects. Methods Serum samples were obtained from 20 non-sensitized subjects and 23 sensitized patients divided in three groups according to their response to peanut oral challenge (no response or response to high or low doses, respec tively). Peanut-specific IgG, IgG subclasses, IgA and IgM were assayed usin g an ELISA, and their reactivity against peanut proteins tested using Weste rn Blot. Results A large dispersion of antipeanut antibody levels was observed in th e three groups of patients, high levels of I,oc, IgG1, IgG4 and IgA usually correlating with highly positive radioallergosorbent test (RAST). Such hig h levels were observed at onset in four patients who underwent peanut immun otherapy who had side effects and poor efficiency. Western blotting demonst rated that: the polyisotypic response observed was directed to several pean ut antigens, including the major allergens, Ara h1 and Ara h2. Conclusion peanut-sensitized patients who spontaneously develop specific Ig E, display polyisotypic-specific antibody responses, whatever their respons e to oral challenge. This might explain the poor efficiency of peanut rush immunotherapy attempts.