Can interleukin-10 be used as a true immunoregulatory cytokine?

Interleukin-10 (IL-10) is a cytokine that is currently regarded as a potential therapy for inflammatory diseases involving T helper 1-type responses because of its ability to downregulate several major functions of Th1 cells and macrophages. There are also evidence that IL-10 could be useful in controlling Th2-mediated inflammatory processes. However IL-10 has also immunostimulatory properties especially on B-cells and activated CD8+ T cells. These pleiotropic effects may explain the discrepancy observed after IL-10 treatment in different in vivo experimental models. We have recently shown that IL-10 induces the differentiation of a subset of regulatory CD4+ T cells (Tr1). In different in vivo models, these cells were shown to inhibit Th1 and Th2-type inflammatory responses through the secretion of IL-10. These Tr1 cells may thus be used in specific cellular therapy in order to deliver IL-10 precisely at the site of inflammation.