Interleukin 10 (IL-10) is a homodimeric cytokine, produced by activated monocytes and T cells, that is deeply involved in the regulation of inflammatory responses and immune reactions. Its main overall function is best described as dampener of immune responses, but IL-10 possesses stimulatory activities as well. Clearly, IL-10 is pleiotropic and research into its many functions and mechanisms of action is still very active. It affects not only the immune system, but through its modulation of growth factors, cytokines and other mediators, it can influence many physiological processes, including for example angiogenesis. lumorigenesis and infection. It is a key molecule that is able to ameliorate potential pathological autoimmune processes through the inhibition of many facets of the inflammatory response. In addition, the induction of regulatory T cells by IL-10 points towards a crucial role in the establishment of peripheral tolerance. All these qualities make IL-10 a desirable candidate to use in clinical intervention and studies examining the efficacy of IL-10 in several chronic inflammatory or autoimmune diseases are well underway.