Interleukin-10 is a pleiotropic cytokine playing a critical role as a regulator of myeloid and lymphoid cell function. Due to the ability of IL-10 to blocking cytokine synthesis and many accessory cell functions of antigen-presenting cells such as macrophages this cytokine is a potent suppressor of the effector functions of macrophages, T-cells and NK cells. IL-10 also participates in regulating proliferation and differentiation of B-lymphocytes, mast cells and thymocytes [1].