Minor salivary gland immunohistology in the diagnosis of primary Sjögren's syndrome.

Background:  Focal lymphocytic infiltrates of minor salivary glands are considered target-organ related signs of Sjogren’s syndrome. The percentages of plasma cells expressing IgA, IgG and IgM in minor salivary gland biopsies have also been suggested as useful in establishing a diagnosis of Sjogren’s syndrome, and this study aimed at evaluating this method. Methods:  All biopsies from patients under investigation for Sjogren’s syndrome (n = 210) at our department during 4 years were analyzed for IgA, IgG and IgM producing cells by immunohistochemistry, and related to Sjogren classification parameters. Results:  A focus score ≥1 was observed in 67/210 patients and the frequency of IgA producing cells was <70% in 42/210 patients. Sufficient clinical data for classification of disease were available for 57/210 patients. Patients were classified as having primary Sjogren’s syndrome (pSS) (n = 9), secondary Sjogren’s syndrome (sSS) (n = 12) or non-Sjogren’s syndrome (non-SS) (n = 36). IgA expressing cells were significantly decreased (P < 0.01) and IgG expressing cells significantly increased (P < 0.02) in patients with pSS compared to non-SS. Also, increased numbers of salivary gland IgG producing plasma cells correlated with increased IgG serum levels (P < 0.001). However, there was no significant difference between sSS and non-SS with regard to IgA, IgG or IgM expressing cells in the glands. Conclusions:  Our results support previous reports indicating the relevance of quantitative evaluation of Ig isotype expression in plasma cells in the clinical investigation of Sjogren’s syndrome and further indicate a difference in plasma cell populations between pSS and sSS.