Figure 2. Mechanisms by which mast cells may promote fibroblast proliferation and collagen deposition. FGF, fibroblast growth factor; IL-4, interleukin-4; PAR-2, proteinase-activated receptor 2; TGF-1, transforming growth factor 1; TNF, tumour necrosis factor ; tPA, tissue-type plasminogen activator; uPA, urokinase plasminogen activator.