Transforming growth factor‐β1 in rheumatoid synovial membrane and cartilage pannus junction

Transforming growth factor (TGF)‐β has been shown to promote tissue repair and have immunosuppressivc actions, and has been proposed to have a role in rheumatoid arthritis (RA). Using immunohistochemical techniques with rabbit F(ab′)₂ antibodies raised against recombinant human TGF‐β1, we have detected TGF‐β1 in the synovial tissue and cartilagc/pannus junction (CPJ) from 18/18 patients with RA. TGF‐β1 was found predominantly in the thickened synovial lining layer in RA. but also detected in a peri vascular pattern in the synovial interstitium as well as in occasional cells in the lymphoid aggregates. At the CPJ it was found both in cells at the distinct junction as well as in the transitional region of the diffuse fibroblastic zone. The cells staining for TGF‐β1 were identified by double immunofluorcsccnce staining as being from the monocy te/macrophage scries as well as the type B synovial lining cells. TGF‐β1 was also detected in the synovial membrane sections from 4/4 patients with systemic lupus erythematosus/mixed connective tissue disease and 5/8 patients with osteoarthri‐tis, in a similar distribution to that seen in RA, and in the lining layer of 1/7 normal synovial membranes. These results add to histological evidence confirming that TGF‐/β1 is present in RA synovial cells and those from otherarthritides. The distributions of TGF‐/β1 in RA synovial membrane reflects its known actions, as it can be detected at the CPJ, where it could induce repair, and close to activated cells upon which it may exert an immunosuppressivc action.