Activated macrophages upregulate surface expression of common cytokine receptor gamma chains (gammac, CD132), triggering of which induces secretion of proinflammatory cytokines. Rheumatoid synovial tissues contain a number of macrophages that play a pathogenic role by secreting proinflammatory cytokines. We studied the expression of gammac in the rheumatoid synovial tissues.
Cryosections of synovial tissues from patients with active rheumatoid arthritis (RA) or with osteoarthritis (OA) were stained with an anti-gammac Mab. Single-cell suspensions from the rheumatoid synovial tissues were stained with the same antibody and an anti-CD14 monoclonal antibody (Mab) for 2-color flow cytometric analysis. A soluble form of gammac in synovial fluids collected from rheumatoid or OA joints was quantitated by ELISA.
Rheumatoid synovial tissues, but not the OA tissues, expressed gammac at a high level. Flow cytometric analysis showed that gammac were expressed by virtually all CD 14 positive synovial cells in RA. Synovial fluid derived from the rheumatoid joints contained a high concentration of soluble gammac.
Membrane bound and soluble forms of gammac are abundant in rheumatoid joints. They might play a complex role in the pathology of RA.