It has been suggested that osteoarthritis (OA) is induced by mechanical stress followed by cartilage destruction, and it is generally accepted that there is little involvement of an immune response in OA compared with that in rheumatoid arthritis (RA). We have previously found clonally expanded transcripts of Vbeta chain of the T cell receptor (TCR) in the synovium of patients with OA. To test the hypothesis that an immune response is involved in OA, we determined: (a) whether CD3+, CD4+, and CD8+ T-cells were infiltrating the synovial membrane of patients with OA; (b) the Th1/Th2-type cytokines produced at the protein level in the synovium of patients with OA.
Immunohistochemical analysis was performed to identify T-cells that infiltrated the synovium of patients with OA using specific antibodies against CD3+, CD4+, and CD8+ T-cell differential antigens, interferon-gamma (IFN-gamma as a marker for Th1 cells, and interleukin-4 (IL-4) as a marker for Th2 cells.
CD4+ T-cells were strongly detected in the sublining layer of the synovium of patients with OA compared with the number detected in the same synovial layer of normal subjects. The number of IFN-gamma+ cells was significantly higher than that of IL-4+ cells in the synovium of patients with OA (P< 0.05).
These observations suggest that Th1 cells predominate in the synovium of patients with OA, which clearly indicates that immune regulation occurs and may play critical roles in inflammation and cartilage destruction in patients with OA.