Sjögren syndrome: comparative studies in local ocular and serum immunoglobulin concentrations with special reference to secretory IgA.

The objective of the present study was to examine Secretory IgA in tears and serum of Sjögren patients (34 patients and 23 controls). The test was performed in a parallel study using a polyclonal and a monoclonal method (Inter-Assay variation 9.1/Intra-Assay variation 5.5). No differences in the levels of tear secretory IgA were found between patients and controls. In serum however, secretory IgA, total IgA, IgM and IgG showed a significant increase in the Sjögren patients. The fact that secretory IgA levels remain normal in the ocular mucosa of these patients may explain that, despite the autoimmune destruction of the lacrimal gland, humoral defense factors are normally present on the surface of the eye to combat infections.