Stress-related illness and the immune system

the immune system
1. the immune system consists of a complex network of cells and chemicals and protects us against diseases and illnesses. The immune response is triggered by antigens- substances that the body recognises as foreign. Some antigens, such as pollen or house dust, can be harmless to some people but provoke allergic responses to others. Antigens can also be carried on the surface of harmful disease-causing pathogens, such as viruses, bacteria and fungi
2. white blood cells, known as lymphocytes and phagocytes, are particularly important in the immune response and protect us in 3 different ways
  1. 1. non-specific immunity
    1. phagocytes, such as macrophages, surround and ingest foreign particles. Macrophages scout for pathogens and alert other macrophages to an invasion when it detects them. They can also alert lymphocytes called helper T cells
  2. 2. cell-based immunity
    1. T cells, made in the thymus gland, find and destroy cells that they identify as foreign or infected. They activate killer cells known as cytotoxic T cells, which destroy infected cells and activate lymphocytes called B cells
  3. 3. antibody-based immunity
    1. B cells, made in the bone marrow, attack invading substances in the bloodstream before infections even reach cellular or tissue level. The B cells form plasma cells, which make antibodies that bind to viral antigens and slow them down so that they can be destroyed more easily
Stress-related illness
1. our bodies are designed to react to stress but not for long periods. Immune system functioning can be reduced by both acute and chronic stress, although chronic stress is more dangerous
2. acute stress and the immune
  1. as the acute stress response is designed to be short-term the immune system should not be dangerously weakened by short periods of stress. However, even short-term stress can cause some problems
  2. in a natural experiment Kiecolt-Glaser et al. (1984) monitored T cell activity in the blood of 75 medical students one month before, during, and one month after their final exams and found that it was reduced
    1. this means that immune responses could also be reduced, leaving the students more vulnerable to illness
    2. in evaluating these findings, there are several points to make
      1. medical students might be unlike other students, limiting the generalizability to other groups
      2. Kiecolt-Glaser et al. (1984, 1991), found further support for their conclusions in carers of people with Alzheimer's disease and in women going though divorce
      3. further evidence was provided by Marshall et al. (1998), who found that short-term stressors, such as exams, can slow recovery by reducing the production of cytokines, which promote wound healing
      4. acute stress alone may not explain the findings, as it was also found that the presence of co-existing long-term stressors, such as loneliness, could exacerbate the effects of acute stress
3. chronic stress and the immune system
  1. interpersonal conflict
    1. Cohen (2005) showed that couples in conflict that had lasted for more than a month were especially vulnerable to succumbing to infection when exposed to an infectious agent
    2. Kiecolt-Glaser (2005) supported the idea that immune responses are reduced by showing that blisters on the arms of couples healed more slowly after conflicting discussions compared to after supportive ones.
    3. others, such as Mayne et al. (1997), have suggested a gender difference in that women in conflicting couples show stronger immune suppression
  2. death of a close relative
    1. Gerra et al. (2003) showed lower natural killer cell and lymphocyte activity in bereaved people compared with matched controls. This difference was still present 40 days after the bereavement and persistent in some individuals for months
      1. Kiecolt-Glaser and Newton (2001) noted a greater effect for widowers
  3. Caregiving
    1. Kiecolt-Glaser et al. (2000) found that long-term care of a dependent relative was associated with lower levels of killer cell activity and poor resistance to viral infection in caregivers compared with matched non-caregivers
Evaluation of studies of the effect of stress on the immune system
1. good experimental suppot
  1. there are many good-quality, experimental studies (as outlined above) that give clear evidence for changes in immune system to both acute and chronic stress
2. reductionism
  1. to reduce the impact of stress to something that is purely physiological/ biological ignores the whole person and the sociocultural context in which they live. Many other factors that are difficult to control in research could be involved, such as depression, anxiety, level of social support and cultural tolerance of weakness
3. individual differences
  1. some of the studies described here have suggested that variables such as gender might mediate responses to stress. In addition, age or personality factors could make people vary in vulnerability and would need to be controlled if the effects of stress are to be clearly understood

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Stress-related illness and the immune system

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	Creado por Bethan Stevenson hace más de 10 años