The Immune System and the Nervous System
Evidence is mounting that the immune system and the nervous system are linked in several ways. One well-known connection involves the adrenal glands. In response to stress messages from the brain, the adrenal glands release hormones into the blood. In addition to helping a person respond to emergencies by mobilizing the body’s energy reserves, these “stress hormones” can stifle the protective effects of antibodies and lymphocytes.
Another link between the immune system and the nervous system is that the hormones and other chemicals that convey messages among nerve cells also “speak” to cells of the immune system. Indeed, some immune cells are able to manufacture typical nerve cell products, and some lymphokines can transmit information to the nervous system. Moreover, the brain may send messages directly down nerve cells to the immune system. Networks of nerve fibers have been found connecting to the lymphoid organs.