See article on page215 Cytokines are small glycoprotein mediators involved in communication between cells. Immunological responses are, to a high degree, regulated and directed by specific cytokines. The simultaneous action of different cytokines, as well as their sequential interaction with target cells, seems to be of pivotal importance for an efficient host defence reaction. In inflammation, pro-inflammatory cytokines (that is, tumour necrosis factor-α (TNF-α), interleukin (IL)-1, IL-8, and IL-12) which initiate and perpetuate the activation of immune and non-immune cells are counterbalanced by contra-inflammatory mediators. According to this scheme, human T helper cells have also been functionally divided into those producing cytokines which augment immune activation (IL-2 and interferon-γ, which are attributed to type 1 T helper cells) and those secreting immunoregulatory interleukins (IL-4, IL-5, IL-10, and IL-13 by type 2 T helper cells). Interleukin 10, previously named cytokine synthesis inhibitory factor (CSIF), has, like many other cytokines, multiple biological effects. Its main immunoregulatory function seems to be the inhibition of effector functions of activated phagocytes (monocytes, macrophages, granulocytes), T cells and non-immune cells. Human IL-10 down regulates transcription and secretion of IL-1β, IL-6, IL-8, TNF-α, and G-CSF by activated monocytes and macro- phages.1 …