Characterization of IgE and IgG epitopes on ovomucoid using egg-white-allergic patients' sera.

To investigate the importance of linear and conformational structure and carbohydrate chains in hen ovomucoid epitopes, the IgG and IgE binding activities of three native and reduced carboxymethylated (RCM) domains (DI, DII, and DIII) were compared using human sera from egg-white-allergic patients. There was significantly more IgG and IgE binding activity to DIII than to DI and DII. The IgG binding activity to RCM domains was similar to the native form, while RCM-DIII had significantly greater binding activity to IgE antibody (p < 0.05). It indicated that the main IgE and IgG epitopes on each domain were of linear structure. However, the total reactivity of the three domains was estimated to be about 50-60% (IgG binding) and 55-75% (IgE binding) compared with total reactivity in ovomucoid, resulting in some ovomucoid epitopes consisting of conformational epitopes on domain I-II or II-III. The carbohydrate moieties in DIII had a rather inhibiting effect on its IgG and IgE binding activities.