Human mast cell subsets--distinct functions in inflammation?

That mast cells participate in inflammatory reactions is beyond argument. A major question posed by mast cell biologists is whether specific functions in inflammation are subserved by different subsets of the mast cell population. We have investigated the two major subsets of human mast cells (MC(T) and MC(TC)), in the chronic inflammatory processes associated with rheumatoid arthritis (RA). Whereas normal synovium contains mainly MC(TC) mast cells, the MC(T) subset is selectively expanded in early RA, in numbers that correlate with synoviocyte hyperplasia and T-lymphocyte infiltration. In contrast, in RA of long duration, MC(TC) mast cells predominate in numbers that correlate with clinical indices of rapidity of disease progression. We suggest that MC(T) mast cells participate in active inflammatory events, whereas MC(TC) mast cells may be more relevant in repair or damage to connective tissues.