Cytokine signaling - regulation of the immune response in normal and critically ill states

Cytokines are produced during the activation of innate and acquired immunit y, and are the principal means for intercellular communication of a microbi al invasion. Cytokines serve to initiate the inflammatory response and to d efine the magnitude and the nature of the acquired immune response. The res ponse of critically ill patients to their injury and/or invading pathogens is dependent, in large part, on the pattern of cytokines which are produced . The immunologic response of critically ill patients can vary from a stron gly proinflammatory response, characterized by increased production of tumo r necrosis factor-alpha, interleukin (IL)-1, interferon (IFN)-gamma, and IL -12 to one predominantly of anergy, characterized by increased production o f T(H)2 cytokines, like IL-10 and to IL-4. Therapeutic efforts to modify th e host immune response in critical illness will require a more thorough und erstanding of the cytokine milieu and the factors that determine their prod uction.