Antigens

• Antigens are typically substances foreign to the body such as bacteria, viruses, or other harmful invaders.

• Their primary role is to provoke an immune response in the body.

• An immune response involves the production of antibodies by white blood cells known as lymphocytes.

• When an antigen enters the body, it is identified and bound by a specific antibody, marking it for destruction.

• Each antigen has a unique shape that is recognised by a specific antibody, this is known as the lock and key model.

• The antigen-antibody complex helps to neutralise the harmful effects of the antigen.

• Some antigens can change or mutate their shape, making it harder for the antibodies to identify and bind to them. This is why certain diseases, such as the flu, require new vaccinations each year.

• Some vaccinations work by injecting a harmless version of the antigen into the body. This stimulates the immune system to produce antibodies, providing immunity without causing the disease.

• Self-antigens are antigens that are produced by the body itself. They are usually ignored by the immune system, preventing an attack on the body’s own tissues.

• Autoimmune diseases occur when the immune system mistakenly targets self-antigens.