Immunoglobulin E Specific to Carbohydrate Determinants and Its Relevance in Legume Allergic Cross-reactivity

A glycol-related Immunoglobulin E (IgE) reactivity has been demonstrated in most allergen sources, especially in the plant kingdom. Recent progress in glycobiology has allowed a clear classification of these glycan-epitopes. Unlike classical peptide chain-based epitopes, glycoepitopes can share significant structural homologies beyond the limits of protein families. These glycon epitopes are thus prone to extensive cross reactive and occurs in proteins as distinct as pollen and Hymenoptera venoms. Because a monovalent IgE-binding domain may have low clinical reactivity and sometimes may share with protein epitope to induce allergic symptoms. Many of these glycoepitopes behave as “pan-epitopes” leading to extensive cross-reactivity in serum-based assays, glycol epitopes, and cross-reactive carbohydrate (CCD) are classically considered as a potential source of positive in-vitro results without clinical significance. Reports demonstrated that glycon epitopes could induce a response at the cell level and suggested that they might play a role In-vivo. So, accurate measurement and specificity assessment of CCD-specific IgE is a critical factor to understand the allergenic cross-reactivity and clinical sensitivity mediated by CCD- specific IgE. The present review considers studies with In-vitro allergenic cross-reactivity due to IgE binding may not be a predictive measure of clinical symptoms and that is very true in the case of haptenic or glycan IgE binding of antigens. The CCD and related IgE binding have to be assessed and evaluated for clinical relevance for avoidance by sensitized subjects and also it is required for allergenic assessment before the functional proteins are labeled for allergenicity during the commercialization of food products containing legume CCD-glycoproteins. The legume allergenic cross-reactivity and biological relevance of CCD-specific IgE will provide information for the clinician to review the diagnostic role of IgE to identify allergenicity. It promotes further research to evaluate the clinical relevance of CCD IgE in defining true allergic cross-reactivity among glycoproteins.