MACROPHAGE INFLAMMATORY PROTEIN-1-BETA - A C-C CHEMOKINE IN OSTEOARTHRITIS

The aim of this study was to determine whether the cytokine macrophage inflammatory protein-1 beta (MIP-1 beta) is present and functionally active in the arthritic joint. We used immunoassays and bioassays to a ssess the presence and function of MIP-1 beta using samples obtained f rom 62 arthritic patients. MIP-1 beta levels were increased in synovia l fluids (SFs) from patients with osteoarthritis (OA) (18.0 +/- 8.9 ng /ml) (SD) compared to patients with rheumatoid arthritis (RA) (6.1 +/- 2.9 ng/ml) or other forms of arthritis (10.4 +/- 7.0 ng/ml) (P < 0.05 ). Levels of OA SF MIP-1 beta were significantly greater than OA or no rmal serum levels of MIP-1 beta. Anti-MIP-1 beta neutralized 28% of th e chemotactic activity for monocytes found in OA SFs. Isolated OA syno vial tissue fibroblasts did not constitutively produce MIP-1 beta but could be induced to express this chemokine upon exposure to tumor necr osis factor-alpha, interleukin-1 beta, or lipopolysaccharide. Synovial tissue immunohistochemical staining revealed that the main immunoposi tive cells in OA were the lining cells as well as vascular smooth musc le and endothelial cells. A minority of macrophages were immunopositiv e as well. In this study, we identify MIP-1 beta as a unique cytokine increased in OA compared to RA SF. We conclude that MIP-1 beta may pla y a role in the ingress of monocytes into the OA joint. (C) 1995 Acade mic Press, Inc.