Brain and immune system: A one-way conversation or a genuine dialogue?

The immune system and the nervous system not only share certain characteristics, they also are functionally interconnected. The stressful environmental conditions can modulate immune functions. This implies that the brain can influence the immune system. The responses of both physiological systems have several characteristics in common: (1) communication at a distance, (2) capability to develop memory, and (3) the use of chemical messengers (neurotransmitters, neuroendocrine peptides, and lymphokines) to transmit messages. Two major subsets of lymphocytes can be distinguished that develop from a stem cell localized in the bone marrow. One subset comprises lymphocytes that come to full maturation in the bone marrow itself and hence are called B lymphocytes. Another subset of lymphocytes leaves the bone marrow at an immature stage to spend a period of their life in the thymus. Activation of the immune system by antigenic stimulation induces changes in brain function and in neuroendocrine profiles. Some aspects of the bilateral interaction of central nervous system (CNS) and immune system are discussed in the chapter.