The aim of this study was to determine whether the cytokine macrophage inflammatory protein-1β (MIP1β) is present and functionally active in the arthritic joint. We used immunoassays and bioassays to assess the presence and function of MIP-1β using samples obtained from 62 arthritic patients. MIP-1β levels were increased in synovial 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-1β were significantly greater than OA or normal serum levels of MIP-1β. Anti-MIP-1β neutralized 28% of the chemotactic activity for monocytes found in OA SFs. Isolated OA synovial tissue fibroblasts did not constitutively produce MIP-1β but could be induced to express this chemokine upon exposure to tumor necrosis factor-α, interleukin-1β, or lipopolysaccharide. Synovial tissue immunohistochemical staining revealed that the main immunopositive cells in OA were the lining cells as well as vascular smooth muscle and endothelial cells. A minority of macrophages were immunopositive as well. In this study, we identify MIP-1β as a unique cytokine increased in OA compared to RA SF. We conclude that MIP-1β may play a role in the ingress of monocytes into the OA joint.
ASJC Scopus subject areas
- Immunology and Allergy
- Pathology and Forensic Medicine