Analysis of mast cells in rheumatoid arthritis and osteoarthritis by an avidin-peroxidase staining.

As demonstrated by labeling with peroxidase, avidin was found to bind selectively and distinctly to mast cell granules. Inhibition studies suggested that avidin is bound by heparin. Based on this new mast cell staining procedure, mast cell distribution in the inflamed synovium of rheumatoid arthritis (RA) and osteoarthritis (OA) has been investigated. In the subsynovial layer, a significant decrease in mast cell numbers was observed in RA-synovium when compared with OA-synovium. This decrease correlated with the presence of lining cell ulcers and granulation tissue and can be interpreted as the result of mast cell degranuation induced by complement-mediated or immune complex-triggered mechanisms.