reasing the number of CD8 cells and suppressing immune function. Individuals fall into categories..those who are "high reactors", and those who are "low reactors". High reactors are significantly affected by stress, as shown by a significant increase in heart rate, blood pressure, catecholamines, and CD8 cells. Low reactors show little or no change in those areas (p. 111). Catecholamines are chemicals produced by the body that work in nerve transmission. The three main catecholamines include dopamine, epinephrine and norepinephrine. Dopamine raises the heart rate and blood pressure, epinephrine raises heart rate and opens blood vessels (thereby lowering blood pressure); and norepinephrine closes blood vessels (thereby raising blood pressure) (Glaser, 1996). Epinephrine and norepinephrine are the catecholamines most commonly measured in stress experiments, and both increase under stress. Increases such as these can suppress aspects of immune function, including natural killer cells (cells that attack antigens without having recognised them first) activity. Increases in catacholemines may also rapidly alter cell numbers via redistribution. Changes in epinephrine levels are also thought to reflect lymphocyte migration from bone marrow, the extremities, and the thymus to other parts of the body (Gallagher et als., 1995; Naliboff, Benton, Solomon, Morley, Fahey, Bloom, Makinodan and Gilmore, 1991). All of the above supports the argument that there is an inter-relationship between stress and immune system functioning, and that this interaction can be measured. Or to word it another way, there is a clear causal relationship between the cognitive (stress in this case being the manipulated independent variable), and the physiological (the immune system which is being manipulated). Any variable which affects the normal immunocompetence of the immune system (wellness), thus impacts on health outcomes (illness/low wellness). Much anecdotal evid...
