Immunohistochemical characterization of the cellular infiltrates in Sjögren's syndrome, rheumatoid arthritis and osteoarthritis with special reference to calprotectin-producing cells.

The aim of this study was to analyse the nature of infiltrating cells in minor salivary glands of patients with Sjögren's syndrome (SS). Furthermore, we wanted to characterize the tissue distribution of calprotectin-producing cells in inflamed salivary gland tissue of SS and in synovial tissue of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Cryostat sections of labial salivary gland tissue from patients with SS and synovial tissue from RA and OA patients were stained (ABC-immunoperoxidase technique) using monoclonal antibodies (MoAbs) to T cells (CD3), monocytes/macrophages (CD14, CD68), and calprotectin. Monocytes and macrophages were widely distributed in focal infiltrates of salivary gland tissue from SS patients. Calprotectin markers showed a distinct staining of infiltrating macrophages and around blood vessel walls. In synovial tissue samples, calprotectin was expressed in a high percentage of cells in the synovial lining, the subsynovium, and vessel walls. The percentages of cells stained for calprotectin were significantly higher in RA than in OA and SS tissues. Antibodies to the calprotectin complex stained cells with a similar distribution as antibodies against the separate polypeptide chains of calprotectin. The localization and differentiated expression of calprotectin in these chronic inflammatory conditions indicate a role in the inflammatory process and may be an additional marker of macrophages/granulocytes in SS, RA and OA.