Focal lymphocytic infiltrates of minor salivary glands are considered target-organ related signs of Sjögren'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 Sjögren's syndrome, and this study aimed at evaluating this method.
All biopsies from patients under investigation for Sjögren's syndrome (n = 210) at our department during 4 years were analyzed for IgA, IgG and IgM producing cells by immunohistochemistry, and related to Sjögren classification parameters.
A focus score >or=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 Sjögren's syndrome (pSS) (n = 9), secondary Sjögren's syndrome (sSS) (n = 12) or non-Sjögren'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.
Our results support previous reports indicating the relevance of quantitative evaluation of Ig isotype expression in plasma cells in the clinical investigation of Sjögren's syndrome and further indicate a difference in plasma cell populations between pSS and sSS.