Serotonin, cytokines, p11, and depression.

F or at least four decades, the field of psychoimmunology has attracted numerous investigators based on diverse hints linking the immune system to emotional behavior. The administration of cytokines for the treatment of various diseases is often associated with depression, which frequently accompanies autoimmune disease. Now, in PNAS, Greengard and colleagues (1) report a specific molecular pathway linking cytokines and the actions of antidepressant drugs. Their findings confound established wisdom, as they imply that brain cytokines exert antidepressant actions and mediate the influences of the principal serotonin-specific reuptake inhibitor (SSRI) antidepressant drugs. How the present discoveries fit into the context of our understanding of antidepressant actions can be summarized as follows.