Modulation of host defense by the neuropeptide alpha-MSH.

alpha-melanocyte stimulating hormone (alpha-MSH), a peptide that occurs within the brain, the circulation, and other body sites, is a potent antipyretic agent when given centrally or peripherally. The peptide likewise inhibits inflammation and aspects of the acute-phase response. The combined evidence suggests that alpha-MSH molecules act as natural modulators of host reactions by antagonizing the central and peripheral actions of cytokines.