Question

Briefly explain the various types of disorders arising from improper function of the immune system.

Answer 1

Improper functioning of the immune system gives rise to three groups of disorders:

1. Allergies or hypersensitivity: The exaggerated response of the immune system to certain harmless antigens (allergens) such as pollen, dust, feathers and fungal spores. The antigen-antibody reaction on mast cells causes them to burst and release histamine, which causes dilation of capillaries, rashes, watery eyes, running nose, sneezing or breathing difficulty; in severe cases it may cause anaphylactic shock which can be fatal. Anti-histamine drugs and steroids relieve the symptoms.
2. Autoimmune diseases: The self-recognition system fails and the body starts making antibodies against its own antigens, destroying its own cells. Examples: myasthenia gravis (muscles destroyed), multiple sclerosis (myelin sheath of nerve cells attacked), rheumatoid arthritis, insulin-dependent diabetes, chronic hepatitis.
3. Immunodeficiency diseases including SCID: The immune system is deficient, so the person is highly prone to infections. In SCID (severe combined immunodeficiency), both T cells and B cells are absent or negligible at birth, so even a small infection can be fatal; children are kept in isolation suits. AIDS is another important immunodeficiency disease caused by HIV, which destroys T-helper cells.

Thus allergies, autoimmune diseases and immunodeficiency diseases are the three broad categories of immune system disorders.