CYTOKINES FOR PSYCHOLOGISTS - IMPLICATIONS OF BIDIRECTIONAL IMMUNE-TO-BRAIN COMMUNICATION FOR UNDERSTANDING BEHAVIOR, MOOD, AND COGNITION

The brain and immune system form a bidirectional communication network in which the immune system operates as a diffuse sense organ, informi ng the brain about events in the body. This allows the activation of i mmune cells to produce physiological, behavioral, affective, and cogni tive changes that are collectively called sickness, which function to promote recuperation. Fight-flight evolved later and coopted this immu ne-brain circuitry both because many of the needs of fight-flight were met by this circuitry and this cooptation allowed the immune system t o respond to potential injury in anticipatory fashion. A?any sequelae of exposure to stressors can be understood from this view and can take on the role of adaptive responses rather than pathological manifestat ions. Finally, it is argued that activation of immune-brain pathways i s important for understanding diverse phenomena related to stress such as depression and suppression of specific immunity.