The Immune system - Stress Related Illness Flashcards
What is the immune system?
network of cells and chemicals throughout the body that functions to seek out and destroy invading particles
What are antibodies?
– (produced by lymphocytes) attach themselves to foreign bodies to slow them down, making it easier for phagocytes to engulf them
What are white blood cells?
[A.K.A Leucocytes]
there are two types of White blood cell = PHAGOCYTES (surround and engulf foreign particles) and LYMPHOCYTES (produce antibodies)
What is an antigen?
Anything that stimulates an immune response, e.g. bacteria, fungi, viruses, toxins and parasites
Information on hormones:
> Hormones are believed to be responsible for the negative effects of stressful situations
• Hormone supplies are rarely exhausted – even under the most severe pressure
• We know far more about the widespread effects of these hormones
White Blood Cells = key players in immune system – Lymphocytes + Phagocytes = 3 different mechanisms of immunity
What are the 3 mechanisms of immunity?
non-specific immunity, Cell-based immunity and Antibody based immunity
Elaboration of the 3 mechanisms of immunity…
- Non-specific immunity – phagocytes surround and ingest foreign particles – e.g. macrophages to destroy invading cells and activating helper T cells
- Cell-based immunity – Lymphocytes, called T cells (mature in Thymus Gland) seek out and destroy any cells recognised as foreign (e.g. in transplanted tissue) and cells infected with antigens such as viruses and bacteria. Helper T cells activate cytotoxic T cells (e.g. natural killer cells) which destroy infected body cells and also activate another class of lymphocyte, the B cell
- Antibody based immunity – B cells (mature in Bone Marrow) destroy invading agents whilst they’re still in the blood stream and before they enter the body’s tissues.
They do this by forming plasma cells which produce antibodies that attach themselves to virus or bacteria, slowing them down to make it easier for them to be destroyed by other immune cells, such as phagocytes and cytotoxic cells
‘Stress response hormones can affect the immune systems directly’ give an example of this
high levels of corticosteroids can shrink the thymus gland, preventing the growth of T cells
What is the immune system differences of short lasting life events and chronic stress?
> Short lasting life events = immunosuppression
>Chronic stress = parallel long term reductions on immune function (Willis et al 1987)
What 3 factors can help to self-regulate immune function, other then resolving the stressful situation?
Exercise, diet and social support
The affects off chronic stress on the immune system mean what?
body = more vulnerable to infection and disease
Give three examples of the effects of stress on the Immune system
- Infection and disease – stress causes physiological changes that weaken our immune system = negative effect on health, infections and illnesses occur more often and recovery takes longer
- Indirect effects – stress causes release of ACTH from the Pituitary Gland in the brain which signals the adrenal glands to release anti-inflammatory hormones. These inhibit immune cell functioning
- Psoriasis and Eczema – Symptoms of inflammatory skin disorders worsen with stress stress interferes with the immune system’s ability to deal with the inflammation associated with these disorders
How the Immune system works
- Virus infects body
- Macrophage engulf and destroy virus
- Macrophage activates helper T cells
- Helper T cells activate Cytotoxic T cells and B cells
5a. Cytotoxic T Cell destroy infected body cells
5b. B cells form plasma cells
6a. Antibodies attach to infected body cells which acts as a signal for their destruction
6b. Plasma cell makes antibodies which attach to antigens
Who did the key study into the effects of stress on the immune system and when?
Kiecolt-Glaser et al 1984
Describe the Kiecolt-Glaser 1984 key study into the effects of stress on the immune system - what was the procedure?
- natural experiment using 75 medical students
- Blood samples were taken
a. one month before their final exams (relatively low stress)
b. during the final exams (high stress) - Immune function was assessed by measuring T cell lymphocyte activity in the blood stream
- The students were also given questionnaires to asses psychological variables such as life events and loneliness
What were the findings and conclusions of the Kiecolt-Glaser (1984) study into the effects of stress on the immune system - involving the blood samples of 75 medical students ?
Findings
• T cell activity was significantly reduced in the second sample (higher stress)
• T cell activity was most reduced in participants who also reported high levels of life events and loneliness
Conclusion
Examination stress reduces immune functions, potentially leaving the individual vulnerable to illness and infection. Psychological variables also affect immune function
How could you evaluate the Kiecolt-Glaser (1984) study into the effects of stress on the immune system - involving the blood samples of 75 medical students ?
This study used medical student who might be considered a non-representative group. This limits the extent in which these results can be generalised to groups in society
What three examples of chronic stressors do you have research support for the effect of chronic stress on the immune system?
Conflict in interpersonal relationships
Death of a spouse
Caregiving
Who did the research into the effects of chronic stress: ‘Conflict in interpersonal relationships’ on the immune system?
Cohen (2005)
Who did the research into the effects of chronic stress: ‘Death of a spouse’ on the immune system?
Gerra et al (2003)
Who did the research into the effects of chronic stress: ‘Caregiving’ on the immune system?
Kiecolt and Glaser (2000)
Describe the effects of chronic stress: ‘Conflict in interpersonal relationships’ on the immune system using research as support
> Couples whose interactions are negative and hostile show less adaptive immunological responses after those interactions
- E.g. individuals who report relationship conflict lasting more than one month have been found to be particularly at risk of developing illness when exposed to an infectious agent (Cohen 2005)
Describe the effects of chronic stress: ‘Death of a Spouse’ on the immune system using research as support
> Associated with immune system dysfunction
Individuals who recently experienced an unexpected bereavement showed lower natural lymphocyte activity compared to matched, non-bereaved controls: (Gerra et al 2003) - observed 40 days after death
> However, caution when interpreting results as it is unclear whether the consequences of bereavement, e.g. lack of sleep and depression, could cause stress and change immune system functioning
> Research also uncovered gender differences; unlike the findings about effects of marital conflict, it is men who appear at greater risk of mortality following the death of their spouse
Describe the effects of chronic stress: ‘Caregiving’ on the immune system using research as support
Kiecolt and Glaser (2000)
>Another form of chronic stressor = caring for a spouse with dementia
>Caregivers are frequently socially isolated; experience overwhelming demands on their resources, both physical and psychological and show higher levels of depression and anxiety
> Compared to control match groups, spousal caregivers show poorer immune function
Contradictory to some research - The effects of stress on the immune system:
Immune system can still work within range
Stress does not necessarily = illness
Explain Cohen’s key study into the effects of stress on the immune system, concerning daily uplifts and hassles, and life changes
Method – Participants filled in a questionnaire on the:
1. Negative life events
2. How stressed they are
3. Degree of negative emotion felt
• Scores were combined to make stress index
• Participants were then exposed to low doses of the common cold virus (ethics!)
Results – 82% of 394 participants became infected with the cold virus and infection was highly correlated with their stress index score.
- the higher the score on stress index the more likely they were to become infected
Evaluation – It was correlational, however it strongly suggests that high levels of stress will reduce immune function and make a person more vulnerable to viral infection
- It ignores individual differences
- No specific causation, just correlational relationship
