Immune Mechanisms Are Important to the Emergence of Defeat Stress–Induced Depressive Behaviors
At a recent scientific meeting, researcher Georgia E. Hodes presented evidence that in mice, the immune system may play a role in behaviors that resemble human depression. Repeated social defeat stress (when an intruder mouse is threatened by a larger mouse defending its territory) is often used as a model to study human depression. Animals repeatedly exposed to social defeat stress start to exhibit social avoidance and lose interest in sucrose. Hodes et al. determined that interleukin 6 (IL-6), an inflammatory cytokine, or signaling molecule, secreted into the blood was crucial to these behaviors. When the researchers injected mice with antibodies that block the effects of IL-6, or when they irradiated the mice’s peripheral immune system to prevent the formation of IL-6, the depressive behaviors did not emerge following defeat stress.
Editor’s Note: There are increasing data that immunological and inflammatory mechanisms play a role in human affective disorders, and these preliminary data raise the possibility that blocking some immune mechanisms more directly in humans could be a novel therapeutic approach to explore in the future.
