Phenotypic characterization of synovial tissue cells in situ in different types of synovitis.

Immunohistochemical double-staining was performed on frozen sections from synovial biopsies obtained at arthroscopy from 22 patients with different kinds of synovitis. Not only in specimens from patients with rheumatoid arthritis and seronegative chronic polyarthritis, but also in those from patients with synovitis due to psoriasis, trauma, or crystals, were seen many alpha Leu-1-positive T lymphocytes--in most cases predominantly of the alpha Leu-3a-positive T "helper" cell type--in close contact with HLA-DR-positive macrophages/dendritic cells. Presence of many HLA-DR-positive, often OKM1-negative, and irregular sublining cells characterized all forms of chronic arthritis.