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Chapter 4

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Department
Psychology
Course
Psychology 2036A/B
Professor
Doug Hazlewood
Semester
Fall

Description
Chapter 4- Psychoneuroimmunology Immunocompetence- the extent to which an immune system is functioning properly to ward off micro-organisms - Glaser and colleagues- found significant declines in immunocompetence (first measured one month before exams, then on their last day of that exam period) Psychoneuroimmunology- the study of the relationship between psychological states and the functioning of the immune system - our psychology (psycho) affects nervous-system functioning (neuro), which in turn affects our immunity to disease (immunology). How Immune-System Function is Measured in Psychoneuroimmunological Research - note that two studies assessing the impact of the same psychological variable, such as exam stress, might come to different conclusions depending on which aspect of immune functioning is being assessed- that which fights off colds or that which kills tumour cells - immune system functioning is dependent on the systems ability to produce, or proliferate, cells to do its work. One simple way of measuring immunocompetence is to count these cells (typically white blood cells) as they exist in the bloodstream. This cell counting is called an enumerative assay and is common in PNI research. Enumerative assay- a lab test done to count cells (typically white blood cells) as they exist in the bloodstream - in studies using cell counts, you will see lymphocyte measures taken from blood samples, counting such white blood cells as NK, T, and B cells. Researchers look for two things in these counts- a minimum number of cells for adequate immune function, and a balance between various cell types, such as different types of T cells. - in general, the better the immune system functions, the higher these counts are. Functional tests of immunity- tests done to assess the immune system at work - functional tests performed on cells outside the body are called in vitro tests. Those performed inside the body are called in vivo tests. - in vitro tests of immunocompetence start with a blood sample that is combined with a substance called a mitogen. A mitogen is a relatively harmless substance that stimulus immune cell activity as though the immune cell were acting against an invading cell or antigen. Three of the most common mitogens used in PNI research are concanavalin A (Con A), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). - Natural Killer (NK) cell activity is also measured through in vitro techniques. Because NK cells perform a 'seek and destroy' function, we measure their activity by exposing NK cells to diseased cells, usually tumour cells. For this reason, PNI research linking psychological variables to cancer often measures NK activity. - After exposure, NK cells are measured in two ways. In one, proliferation is measured through cell counts taken after the introduction of tumour cells. In the other, NK cell effectiveness is assessed by measuring the destruction of tumour cells. In PNI, literature, this second method is often called an NK cell cytotoxic activity assay. This process of killing tumour cells is called NK cell lysis because to lyse a tumour cell means to destroy it. NK cell cytotoxic activity assay- a test in which the proliferation and effectiveness of NK cells is measured after they have been exposed to diseased cells NK cell lysis- destroying tumour cells by exposing them to NK cells - There are also many common types of in vivo functional tests of immunocompetence - In one of these tests on the herpes virus, Ab (antibody) levels are measured, whose job it is to flag herpesvirus for destruction. The more suppressed the immune system, the more herpes virus, and thus more Ab. This means that when herpesvirus-specific antibodies are measured, the higher the Ab count, the poorer the immune system functioning. - In other in vivo tests researchers can also introduce an antigen into the body and measure the specific Ab activity meant to deal with that intrusion. The skin is then observed- if the immune system is working properly, there should be swelling and redness. - We can also count antigen-specific Ab produced in response to the injection. This can be done through blood samples or mucous secretions (saliva). One antibody commonly measured in the saliva or mucous is called sIgA (secretory or salivary immunoglobulin). **Note- in herpesvirus studies, higher Ab counts indicate immunosuppression. In injection studies, more Ab indicates better immunocompetence. Acute stressor- a stressor that is immediate in its duration and proximity. - in labs, effects of an acute stressor are measured through blood samples taken just before, just after and then some time (i.e. hours) after the stressor has been introduced. - acute stressors can actually enhance immune function by stimulating non-specific, or innate, immunity while suppressing specific immunity. Chronic stress however suppresses both specific and non-specific immunity and is linked to premature aging. Research in Pyschoneuroimmunology: Providing Evidence for a Biological Link Between Psychology and Health - the general findings show that symptom complaint goes up at stressful times (i.e. exam period) and that cellular measures of immune response indicate immunosuppression. Exams are examples of acute stressors. - while it may take days for the immune system to react to an antigen, it takes as little as five minutes for a stressor to inhibit the ability of the immune system to engage that response. Lab studies have also shown that the effect of stressors on immune functioning is stable over time for a given individual, leading to the conclusion that there are dispositional or personality factors that influence the extent to which a stressor affects immunity. - Boscarino study- (veterans with PTSD and veterans without PTSD); those who had suffered from PTSD were more likely to suffer from a wide range of medical problems, including circulatory, digestive, musculoskeletal and metabolic ailments. The worst were nervous system disorders which PTSD veterans were 2.47 times more likely to suffer from and non sexually-transmitted infectious diseases, which they were 2.14 times more likely to contract. (good study as he controlled for other factors and since he followed up with them 20 years later, he demonstrated that severe stress exposure can have long-term effects) - survivors of hurricane Andrew in the US, showed disruption in their sIgA counts and those who lived through an earthquake in Northridge, Cali., showed a positive correlation between immunocompromise and the degree of distress experienced up to four months after the quake - Kiecolt-Glaser and colleagues; found that women who had gotten divorced or separated in the past year had significantly poorer functioning on five of the six immune-system measures compared to women who were neither divorced nor separated. In a subsequent study it was found that those who initiated the divorce reported better health than those whose partner had initiated it. Stress and upper respiratory infection Upper respiratory infection- one of a collection of illnesses, such as colds, coughs and bronchitis - URI might be the most common type of illnesses worsened by stress (possibly due to a low production of sIgA, which provides immune defence in the mucus and saliva). - people with generalized anxiety disorder experience greater impact from stressful event- their stress intrusion scores are high. Stress-intrusion scores- a measure of the impact a stressful event has on a persons life. - La Via and colleagues- took in vitro measures of lymphocyte activity and kept track of the number of URI-related sick days the subjects reported. People with generalized anxiety disorder had higher stress intrusion scores, less lymphocyte activity, and almost three more times sick days than the control group (this study showed that lymphocyte activity was correlated with URI sick days and with stress intrusion). Focus on Canadian Research 4-1; Have you had your flu shot? Using vaccinations to measure immune responses within the body - participants in a study were given a flu vaccine and then had to report four times per day (two days before vaccine, and 10 days after it) various mood and physical symptoms. Blood samples were also taken. Found that higher reports of stress were associated with lower levels of antibody production. It was also found that sleep reports were also correlated with stress reports. Also, the critical period for stress to effect immune response was between 8-10 days after the shot had been administered. Other research using this same methodology has shown that students who score higher on measures of loneliness had lower antibody responses to vaccination. Viral challenge studies- studies in which volunteer subjects are intentionally exposed to controlled dosages of upper respiratory infection viruses and environmental stressors to measure the clinical progression of the virus and the response of the immune system. - in one of these studies, participants were exposed to a safety-tested clinical dose of a virus via nasal drops. Immune cells called cytokines were assessed in those who developed infections. Those with lower positive emotional style had greater objective and subjective signs of illness and poorer production of particular interleukins. - Myazaki and colleagues; found that social support did help reduce the harmful effects of stress of the immune system. Social support was positively correlated with NK production. - Evans et. al; found that positive life events can also increase vulnerability to URI, independent of personality measures or health-related behaviours - Major life event stress often results in immunosuppression Stress and autoimmune disease - autoimmune diseases include rheumatoid arthritis, insulin dependent diabetes, and multiple sclerosis. - studies of children who have suffered abuse have found that the post-trauma
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