First 257 words of the document:
Negative effects of stress on the immune system.
One negative effect of stress on the immune system is the reduced NK cell activity. NK cells protect
against cancer cells as well as viruses. A study done by Kiecolt Glaser researched into NK activity in
students one month before exams and during exam period. She found that NK activity was
significantly reduced in the blood samples taken during exam period. This suggests that stressors will
reduce the immune system functioning, increasing vulnerability to illness.
A second negative effect of stress on the immune system is how it influences the balance between
Th1 (an aggressive response to antigens) and Th2 a less aggressive response. When one is active the
other isn't, Th2 works throughout the day whilst th1 through the night, stress can influence this
balance. Stress can cause Th2 to become more dominant, this would mean our immune system would
be less aggressive and therefore vulnerable to illness.
Another negative effect of stress on the immune system is the hormone cortisol being released in
the HPAC response to stress. High levels of cortisol change the activity of lymphocytes (a type of
white blood cell). Arnetz et al studied unemployment in Sweden and found a significant decrease in
lymphocyte response to antigens. This suggests that stress such as being unemployed impairs the
immune system being able to produce lymphocytes and their response to antigens meaning more
susceptible to become ill.