IgE binding to almond proteins in two CAP-FEIA-negative patients with allergic symptoms to almond as compared to three CAP-FEIA-false-positive subjects

Background: Allergy to almonds has been frequently reported, but data on th e identification of the almond allergens, as well as on the reliability of the methods for in vitro detection of specific IgE for these allergens, are scant. This study aimed to identify the almond allergens and to evaluate t he reliability of the CAP-FEIA as the standard system for detection of almo nd-specific IgE with clinical significance. Methods: Immunoblotting performed with an almond-protein extract was carrie d out on the sera of five patients who had previously been tested by the CA P-FEIA system; two of these patients had tested negative with the CAP-FEIA system but suffered life-threatening laryngeal edema after eating almonds, whereas the other three subjects, who had tested positive with CAP-FEIA, di d not present any symptoms subsequent to almond ingestion. Results: The sera of the two symptomatic CAP-FEIA-negative patients had IgE that bound only to a 37-kDa protein in immunoblotting. On the contrary, th e sera of the three asymptomatic subjects all showed IgE binding to two alm ond proteins of 62 and 50 kDa, corresponding to the glycosylated components of the extract. Conclusions: The results here presented suggest that, at least for the exam ined subjects, the positivity to almond, as measured with a standard labora tory method, is due to the presence of the 62/50-kDa glycoproteins with lit tle or no immunologic significance, and not to the binding to the 37-kDa po lypeptide, which appears to be a true almond allergen.