The role of the immune system in synchronizing physiological processes.

To maintain homeostasis of the human organism, intercellular interactions must occur with a high degree of synchrony and coordination. Traditionally, the nervous and endocrine systems have been considered the primary controllers of internal organ function. Only recently, substantial evidence has emerged indicating that the immune system-beyond preserving the body's structural and functional integrity through defense against external and internal threats-is also capable of regulating, coordinating, and synchronizing the activity of tissues, organs, and systems of organs. This review examines noncanonical functions of the immune system that support its consideration as a key coordinator of internal organ physiology. We describe the characteristics of immune-mediated communication and the multiple signaling pathways that enable effective synchronization in the absence of a pronounced hierarchical structure. Examples illustrating how immune cells and biochemical factors coordinate physiological processes are highlighted.