Treatment-induced remission in rheumatoid arthritis patients is characterized by a reduction in macrophage content of synovial biopsies

Objectives. To document the change in synovial membrane macrophage and T-ly mphocyte content in rheumatoid arthritis (RA) patients who achieve remissio n induced by disease-modifying anti-rheumatic drugs (DMARDs). Methods. Arthroscopic synovial biopsies were taken from four to seven sites around a knee joint in 13 patients with RA before and at regular intervals after commencing treatment with a DMARD. The cellular content of synovial membrane biopsies taken at regular intervals for a period of Lip to 3 yr af ter commencing treatment was quantitated by routine histopathology and immu nohistochemical labelling with anti-macrophage (CD68) and anti-T lymphocyte (UCHL-1) antibodies. Synovial biopsies were quantitated with a validated s emiquantitative scoring system and video image analysis. Results. Nine patients obtained clinical remission. as defined by American College of Rheumatology (ACR) criteria. The changes that occurred in the sy novial biopsies included a reduction in lining layer thickness, reduced vas cularity and cellular infiltrate. The most significant reduction in cellula r infiltrate was in the: lining layer macrophages, with less dramatic chang e in the subintimal macrophage infiltrate. Although there was a reduction i n CD45 Re-positive T lymphocytes in the synovial membranes of patients who attained ACR-defined disease remission, it was less significant than the re duction in macrophage content of the synovial membranes and tended to plate au at a reduced level of T-cell infiltration. Conclusions. Remission in RA patients is characterized by a predominant red uction in macrophage content of the synovial membrane, suggesting that curr ent DMARDs may target this cell and its inflammatory mediators.