Stress has therefore been linked to a range of illnesses and research highlight the role
of both a behavioural and physiological pathway. One area of research which
emphasizes the physiological pathway and has received much interest over recent years
is psychoneuroimmunology (PNI).PSYCHONEUROIMMUNOLOGY (PNI)
PNI is based on the prediction that an individual’s psychological state can influence their
immune system via the nervous system. This perspective provides a scientific basis for the
‘mind over matter’, ‘think yourself well’ and ‘positive thinking, positive health’
approaches to life. PNI can be understood in terms of (i) what is the immune system;
(ii) conditioning the immune system; (iii) measuring immune changes; and (iv)
psychological state and immunity.The immune system
The role of the immune system is to distinguish between the body and its invaders and
to attack and protect the body from anything that is considered foreign. These
invaders are called ‘antigens’. When the immune system works well the body is pro-
tected and infections and illnesses are kept at bay. If the immune system overreacts
then this can lead to allergies. If the immune system mistakes the body itself for an
invader then this can form the basis of autoimmune disorders. The main organs of the
immune system are the lymphoid organs which are distributed throughout the body
and include the bone marrow, lymph nodes and vessels, the spleen and thymus. These
organs produce a range of ‘soldiers’ which are involved in identifying foreign bodies
and disabling them. There are three levels of immune system activity. The first two are
called specific immune processes and are ‘cell mediated immunity’ and ‘humoral
mediated immunity’. Cell mediated immunity involves a set of lymphocytes called T
cells (Killer T cells, Memory T cells, delayed hypersensitivity T cells, Helper T cells and
Supressor T cells). These operate within the cells of the body and are made within the
Thymus (hence ‘T’). Humoral mediated immunity involves B cells and antibodies and
takes place in the body’s fluids before the antigens have entered any cells. Thirdly,
there is non specific immunity which involves phagocytes which are involved in non
specifically attacking any kind of antigen. Immunocompetence is when the immune
system is working well. Immunocompromise is when the immune system is failing in
some way.Conditioning the immune system
Originally it was believed that the immune system was autonomous and did not interact
with any other bodily systems. However, research indicates that this is not the case and
that not only does the immune system interact with other systems, but it can be con-
ditioned to respond in a particular way using the basic rules of classical and operant
conditioning. The early work in this area was carried out by Ader and Cohen (1975,260 HEALTH PSYCHOLOGY