Expression of MHC class II antigens and other T cell activation antigens on T cells and salivary duct epithelial cells in the salivary gland of cases of Sjögren's syndrome.

We studied infiltrating T cells and salivary duct epithelial cells in the sublingual glands of 10 patients with primary Sjögren's syndrome (SS) using monoclonal antibodies (MoAb) to T cell subsets (OKT-series), natural killer cells (Leu7) and activation antigens of T cells such as OKT10, OKT9, interleukin 2 receptor (anti-Tac antibody) and major histocompatibility complex (MHC) class II antigens (anti-DR and anti-DQ antigens). DR antigens were identified on salivary duct epithelial cells, suggesting that the cells might function as antigen-presenting cells (APC). Among the salivary duct epithelial cells, OKT8+ cells, which are known to be suppressor/cytotoxic cells, were found in 9 out of 10 patients. Three types of mononuclear cell infiltrations were also evaluated separately: (1) periductal foci, (2) periacinal foci and (3) lymph follicles. We found that the majority of the infiltrating cells in the central portion of the periductal foci were activated T cells (OKT3+, OKT4+, OKIa-1+, DR+ and DQ+), but OKT9, OKT10 and Tac antigens were rarely found in this portion. However, most of the infiltrating cells in the peripheral portion of the periductal foci were OKT10+, and some of them were also positive for OKT9 antigen (transferrin receptor). The results indicated that the T cells in the peripheral portion of the periductal foci are at an early or intermediate phase of activation, whereas the T cells around the salivary ducts are at a later phase. Infiltrating cells in the periacinal foci resembled the cells on the peripheral portion of the periductal foci. Cells within lymph follicles were mainly B cells although scattered OKT4+ or OKT8+ cells were also present.