Figure 2. Potential functions of mast-cell-derived IL-10.
If produced in appropriate settings and amounts, mast-cell-derived interleukin-10 (IL-10) has the potential to promote the development of IL-10-secreting regulatory T cells (e.g., Tr1 cells and CD4+CD25+FOXP3+ T cells) and reduce DC migration, maturation and activation. It can also enhance the ability of DCs to reduce T-cell proliferation and cytokine production through the downregulation of costimulatory molecule expression by the DC. By directly inhibiting tumour-necrosis factor (TNF) and IL-6 production by keratinocytes, IL-10 can indirectly reduce the expression of adhesion molecules on vascular endothelial cells and thereby diminish the recruitment of circulating effector cells. IL-10 can directly inhibit the production of prostanoids by neutrophils and pro-inflammatory cytokines by macrophages. Although many of the specific functions indicated are based on evidence from in vitro studies of IL-10, mast-cell-derived IL-10 has been shown to mediate negative immunomodulatory functions in vivo.