Molecular analysis of IgA in multiple sclerosis.

IgA plays an important role in immune-mediated and anti-viral responses, and is the major antibody in external mucosal secretions. We used enzyme-linked immunosorbent assay (ELISA) and immunoblot to examine IgA in tears and parotid saliva of 21 multiple sclerosis (MS) patients and 19 normal controls. No significant difference in absolute levels were noted and both groups showed a wide range in values. However, 16 of 21 MS patients had detectable changes in molecular form of their IgA. Monomeric IgA was found in 52% of MS tears (P less than 0.001) and 45% of MS parotid saliva (P less than 0.05). Among normals, monomeric IgA was noted in only two saliva samples. IgA in secretions consisted of both A1 and A2 subclasses, although 14% of the monomeric MS IgA samples were restricted to a single subclass. Free secretory component was found in the secretions of all subjects with the exception of a single MS patient. However, immunoblot staining of secretory component was decreased in MS patients compared to controls. This study notes changes in IgA in two distinct external secretions in MS patients compared to controls. These changes are consistent with local mucosal inflammation. Impaired mucosal barriers have important implications in MS with regard to susceptibility to infectious agents, environmental antigen processing, and lymphocyte activation.