Objectives. To present the main functions of interleukin-6 (IL-6) - its role in the immunological response, inflammatory reaction, mood disturbances, and other disease processes.
Review. The advancement in psychoimmunology and psychoendocrinology in the late 20th century fostered a new understanding of IL-6 as one of the key cytokines regulating defense mechanisms. Numerous studies evidenced the important role of IL-6 in the pathophysiology of many disease processes and mood disorders.
Conclusions. Since IL-6 is involved in activation of the mechanisms that control the inflammatory reaction and immunological response, it constitutes an important link in their development. The IL-6 enhances the synthesis of specific antibodies by B lymphocytes, induces differentiation of cells towards cytotoxic lymphocytes, and suppresses proliferation of some neoplastic cells. An even hundredfold increment in the IL-6 level can be seen in inflammatory states and tumors. The IL-6 level is increased also in depressive disorders due to the enhanced activity of the hypothalamic-pituitary-adrenal axis. In consequence there is a rise in the concentration of glucocorticosteroids, leading to an exacerbation of symptoms typical of depressive disorders.