Distribution of IgA1- and IgA2-containing cells in lacrimal glands of patients with Sjogren's syndrome

The human lacrimal gland contains a large number of IgA-secreting plasma cells. The IgA secreted has two subclasses, IgA1 and IgA2, the expression of which is controlled by selective differentiation. The main feature of Sjogren's syndrome (SS) is lymphocytic infiltration into the lacrimal gland. Many cytokines, including interleukin 6 (IL-6) which influence IgA production, might be secreted by epithelial cells and lymphocytic cells in the lacrimal glands of SS patients. Because lymphocytes produce IgA antibodies, differences may exist between normal lacrimal gland and those of SS patients. Lacrimal gland biopsies were performed on 10 SS patients. Four normal controls were biopsied at autopsy. Frozen sections of lacrimal glands from 10 SS patients were studied by a paired immunofluorescence staining of IgA1-IgA or IgA2-IgA. Using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), increased levels of IL-6 mRNA were detected in all SS biopsies in contrast to that of four control samples. Many IgA-containing B cells were found in the interstitium around the normal appearing acini as well as in the lymphocytic infiltration. The proportion of IgA1 to IgA2 was 52% to 48%. This proportion was identical to that previously reported for normal lacrimal glands. In the lacrimal gland of SS, IL-6 mRNA expression was significantly increased compared to the normal lacrimal glands. These results suggest that IgA-containing B cells in the lacrimal gland of SS, which are committed to IgA1 or IgA2 expression, might be increased with the high level of inflammatory cytokines in autoimmune conditions.