Molecular basis for the bidirectional modulation of the neuroendocrine and the immune systems.

Experimental evidence in many fields point towards the existence of a bidirectional communication between the neuroendocrine and immune systems. The immune response unifies the endocrine, nervous and immune systems. This integrated microenvironment includes lymphoid cell, nonlymphoid cells, cholinergic and adrenergic neurons and their neurohumoral products, biologically active substances including the cytokines and lymphokines produced by lymphoid and nonlymphoid cells, hormones and neuropeptides released by endocrine glands and regulatory cells of the brain, membrane and intracellular receptors which make possible the immune connections, and ions which are involved in the transmission of information and the higher nervous system activity which influences the immune microenvironment. Neuroendocrine circuits constitute only one type of efferent link between the brain and the immune compartment. The autonomic nervous system, via its innervation of many peripheral target tissues throughout the body, might also prove to be an important link to the immune system. While the precise mechanism(s) of neuroendocrine-immune relationships may not as yet completely defined, it is apparent that such interrelationships exist.