Immunophysiology: the immune system as a multifunctional physiological unit.

In this review, the immune system is described as a physiological system in its functions and relations with other organs. Hence, communications are mediated by common receptors and cytokines. The immunophysiology is a bidirectional system where the immune system is influenced by endocrine apparatus and vice versa. At the cellular level, we have attempted to define this "cross-talk" by proposing one- or two-signal models, where the first signal is mediated via binding of hormones or neurohormones to the lymphocytes and the second signal is generated by binding of the antigen to the recognition sites or of cytokines to their lymphocyte receptors. The physiological reality of these interrelationships is discussed.