A traditional view, still held by many scientists, is that the immune system is autonomous. That is to say, that it is self-regulatory and functions separate and independent from the rest of the body. With the increasing focus on the relatively new science of Psychoneuroimmunology (PNI), these old views are becoming less legitimate.

The name Psychoneuroimmunology was coined in 1975, by Dr. Robert Ader, director of the division of behavioral and psychosocial medicine at New York's University of Rochester. Dr. Ader believes that there is a link between what we think (our state of mind) and our health and our ability to heal ourselves. In particular, this was borne out in a study conducted by Dr. Ader and his colleagues, which showed that it is possible to classically condition the immune system. The experiment that caused this development consisted of feeding mice with saccharin while simultaneously injecting a drug that caused an upset stomach. It also suppressed the immune system. By association the saccharine with having an upset stomach and nausea, the mice learned to avoid the saccharin. When the experiment was repeated without the drug, Dr. Ader found a high proportion of the mice formally injected died when receiving saccharin alone.

Dr. Ader hypothesized that the conditioning had been so successful that saccharin alone suppressed the immune system enough to kill the mice. It is possible then, that when there is stress on the organism, mental or physical, that there is a corresponding link between the two. That is to say, if a person has a mental state of depression, this state can be interpreted by the body to produce lethargy and other corresponding ailments. Conversely, if the body is diagnosed as ailing from a serious disease, i.e. cancer, a negative mental state may ensue. By conditioning the immune system through mental processes, a connection in communication has been made. Providing the patient with some feeling of control over their circumstances may create a positive outlook and attitude. Some believe that this may, "Inoculate against disease and act as a valuable supplement to conventional medical care."

The Physiological Components in PNI

Psychoneuroimmunology then is the scientific field of study investigating the link between bi-directional communications among the nervous system, the endocrine (hormone) system, and the immune system and the implications of these linkages for physical health. PNI research is looking for the exact mechanisms by which specific brain immunity effects are achieved. Evidence for nervous system–immune system interactions exists at several biological levels.

The immune system and the brain talk to each other through signaling pathways. The brain and the immune system are the two major adaptive systems of the body. During an immune response, the brain and the immune system "talk to each other" and this process is essential for maintaining homeostasis. Two major pathway systems are involved in this cross-talk: the Hypothalamic-pituitary-adrenal axis (HPA axis) and the sympathetic nervous system (SNS).

Research continued in the area of molecular communication between the mind and the body, this however was often seen as unwelcome by the existing science community. Research over the past twenty years has seen the development of Psychoneuroimmunology, which is based primarily upon the neuro sciences of the central nervous systems, the neuroendocrine system and the immune system and their inter-relationships. The central nervous system is a huge array of connections throughout the body incorporating sympathetic and parasympathetic systems. It allows the brain to send information throughout the body via chemicals generally referred to as information substances (IS). It was once thought that the brain sent out these information substances to respond to the various problems in the body and that the communication was that of a one way direction. What has become clear is that the central nervous system virtually controls the body's defense mechanisms. This being said, "Every thought, emotion, idea or belief has a neurochemical consequence".

These natural chemical messengers, called Neuropeptides, were at one time thought to be found in the brain alone. Pioneering research by neuropharmacologist, Candice Pert, revealed that these neuropeptides are present on both the cell walls of the brain and in the immune system. These information substances affect our emotions as well as our physiology. These cells of the body have their own receptors on the surface that act like satellite dishes. These receptors receive the chemical information substances being released by the brain and sometimes return messages at the appropriate times. Pert believes that peptides probably provide solutions to every medical problem. As these complex messengers travel throughout the body, they provide vital information and sometimes almost instant physical feedback. For example, If you have ever encountered something unpleasant, possibly by surprise, you may have found yourself instantly shivering, and then literally shaking off the feeling produced. This is a simple example of how fast the information can be transmitted from thought to physiology. The emotions we create are just that, created. This requires input from the brain. The centre for the brain that deals with emotional issues is the limbic system--in particular the hypothalamus. The discovery by Candice Pert, that neuropeptides and neurotransmitters are also on cell walls of the immune system shows a close association with emotions and suggests that emotions and health are interdependent. Showing that the immune and endocrine systems are modulated not only by the brain but also by the central nervous system itself has had an impact on how we see disease and how it is created. For its part, the endocrine system is a series of hormone secreting glands that themselves moderate the function and balance of the body. Primarily the pituitary, thyroid and adrenal glands send these hormonal chemicals to regulate the function of other organs. Using this network of transmitters and receivers, the body is in constant adjustment to ensure balance.

The balance is kept as long as the immune system is functioning optimally. The immune system is literally on patrol throughout the body and is a complex surveillance system. The immune cells, called Lymphocytes (white blood cells) are the keys to the immune system. Produced initially in the bone marrow of long bones, some of these cells known as stem cells will migrate to the thymus where they multiply and are known as T cells. Those cells that remain in the bone marrow mature to become B cells. Each attacks the enemy in different ways. Circulating the body, when these antigens are discovered an army of appropriate cells (antibodies) is produced to attack the invader. To prevent this army of cells taking over, they in turn are suppressed and attacked. On this continuous patrol, natural killer (NK) cells attack and destroy cells that are produced by the organism which are mutated or abnormal. This action prevents most people contracting cancers or other immune deficient problems such as A.I.D.S.

Implications for PNI

Research has indicated that an inextricable chemical link exists between our emotions, which includes all stress in our lives, both good and bad, and the regulatory systems of the endocrine and immune systems through the central nervous system. This research emphasizes the importance of expressing our emotions both verbally and physically in an appropriate way. When strong emotions generate fear, anger or rage and these are not expressed in a healthy way then the body's natural response is that of the sympathetic nervous system as demonstrated in Cannon's research on homeostasis and the fight or flight syndrome. At this point, inappropriate storing of these stressful emotions produces an excess of epinephrine. This excess of epinephrine causes a chemical breakdown, resulting in internal weakening of the immune system and an increased potential for disease.