Immunologic characterization of the mononuclear cell infiltrates in rheumatoid synovia, in rheumatoid nodules, and in lip biopsies from patients with Sjögren's syndrome.

Two subcutaneous rheumatoid nodules and 8 rheumatoid synovia from patients with rheumatoid arthritis (RA); and 2 parotid glands, 1 "pseudolymphoma," and 6 lip biopsies from patients with Sjogren's syndrome (SS) were studied to identify mononuclear cells. The palisading mononuclear cells in subcutaneous nodules had a surface membrane receptor for complement. B lymphocytes surrounded by larger numbers of non-B lymphocytes were found in RA synovium and between salivary ducts of SS lip biopsies. A "pseudolymphoma" obtained from a patient with SS consisted primarily of B lymphocytes. The predominant mononuclear cell in rheumatoid synovia and salivary glands in patients with RA and SS do not have surface membrane receptors from complement and are thus probably T lymphocytes or null cells.