Q.How does stress affect the immune system?

Stress can cause illness by impairing the immune system, which guards the body against attackers inside and outside. Psychoneuroimmunology studies these links between mind, brain and immune system. The white blood cells (leucocytes), T cells, B cells and natural killer cells, identify and destroy antigens and produce antibodies. Stress reduces natural killer cell cytotoxicity, important in defence against infections and cancer; low levels are found in highly stressed people such as students facing exams and bereaved persons. Negative emotions trigger stress hormones that weaken im …

How stress reaches the immune system

Stress can cause illness by impairing the workings of the immune system. The immune system guards the body against attackers, both from within and outside. Psychoneuroimmunology focuses on the links between the mind, the brain and the immune system, and studies the effects of stress on immunity.

How the immune system works

The white blood cells (leucocytes) within the immune system identify and destroy foreign bodies (antigens) such as viruses, and lead to the production of antibodies. There are several kinds of leucocytes:

• T cells destroy invaders, and T-helper cells increase immunological activity. It is these T-helper cells that are attacked by HIV, the virus causing AIDS.
• B cells produce antibodies.
• Natural killer cells are involved in the fight against both viruses and tumours.

Effect of stress on immunity

Stress can affect natural killer cell cytotoxicity, which is of major importance in the defence against various infections and cancer. Reduced levels of natural killer cell cytotoxicity have been found in people who are highly stressed, including students facing important examinations, bereaved persons, and those who are severely depressed. Studies also reveal that immune functioning is better in individuals receiving social support, and that changes in the immune system have more effect on health among those whose immune systems are already weakened.

The negative-emotion pathway …