Figure 1.

Mast cell (MC) interactions within the transplant during tolerance. FcϵRI activity is inhibited by TGF-β, IL-10 and OX40 ligation. Tregs also inhibit degranulation by lowering intracellular Ca²⁺ levels through increased cAMP. IL-10 suppresses alloreactivity within CD4+ and CD8+ T cells and promote anergy and regulatory functions of CD4+ T cells. IL-10 mediated inhibition of fibroblasts also inhibit subsequent formation of myofibroblasts. IL-10 with co-stimulation of IL-4 decrease MC proliferation, while IL-9 increases proliferation. GM-CSF, granulocyte-macrophage colony-stimulating factor; IL, interleukin; MCP6, mat cell protease 6; SCF, stem cell factor; tDC, tolerogenic dendritic cell; TGF-β, tissue growth factor beta; TNF-α, tissue necrotic factor alpha; Tr1, regulatory T cell type 1 (induced); Treg, regulatory T cell (natural); Blue lines symbolize activating pathways, red lines inhibitory pathways, gray lines symbolize subsequent events. Lighting icons are used in the most profound activation patterns, which are inhibited in tolerogenic environments.