Fig. 1.

Focusing the innate immune response. Insults to the body, from the outside or from the inside, activate cells of the innate immune system. The immune response transmits this information to the brain to cause physiological and behavioral responses. A mild inflammatory response – such as a low-grade infection, trauma (such as dropping a weight on one’s foot) or even strenuous exercise – results in reversible consequences as they are a result of altered cellular (neuron) function. A severe response induces often irreversible consequences as a result of cell death. In either case, the causal event is initiated by monocytic and dendritic cells with the initiation of an inflammatory response.