DNA synthesis in CD4- and CD8-positive cells in synovial fluid of patients with reactive and rheumatoid arthritis.

The occurrence of MHC class I antigens and microbial antigens derived from the triggering infection of the diseased joints in reactive arthritis (ReA) seems to set the stage for local immune activation. In this report activated lymphocytes are demonstrated by using an avidin-biotin-peroxidase complex (ABC) method combined with autoradiography that identifies DNA synthesis and, thus, activation. Most of the activated T lymphocytes in reactive arthritis were found to belong to the CD8 suppressor/cytotoxic T-lymphocyte subset. In striking contrast, the majority of the activated T lymphocytes detected in rheumatoid arthritis (RA) synovial fluid belonged to the CD4 helper/inducer subset. These findings agree well with the assumption that CD8-positive cells identify the foreign antigen in the context of class I antigens, whereas CD4-positive cells are found to be associated with the recognition of MHC locus II coded HLA antigens.