Match List - I with List - II.

Choose the correct answer from the options given below:

A-II, B-III, C-IV, D-I

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. It studies the effects of stress on the immune system. How does the immune system work? The white blood cells (leucocytes) within the immune (antigens) such as viruses. It also leads to the production of antibodies. There are several kinds of white blood cells or leucocytes within the immune system, including T cells, B cells and natural killer cells.

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