Phenotypic characterization of 3H-thymidine incorporating cells in rheumatoid arthritis synovial membrane

Summary Tritiated-thymidine incorporating cells in synovial tissue samples from ten patients with definite or classic rheumatoid arthritis (RA) were studied by combining two techniques. Tritiated-thymidine-labelled cells were seen in autoradiography and simultaneously the subtype of them was determined with immunoperoxidase staining using monoclonal antibodies. Tritiated-thymidine-labelled cells comprised 0.8±0.4% of all the inflammatory cells in RA synovial membrane. Of all ³H-thymidine-labelled cells 34±17% were positive for OKT8 and 19±8% for OKT4 monoclonal antibodies. OKM1-positive cells comprised 7±3% of all ³H-thymidine labelled cells, whereas only a few (3±4%) of them were positive for pan-B monoclonal antibody. This study emphasizes the importance of activated OKT8 lymphocytes in RA synovial membrane.