Question

How do antigens enter the body?

Answer 1

Before discussing the fact that antigens enter our body, we should know what antigens actually are. In a simple definition, antigens are the recognition proteins present in a cell. Almost each and every cell has antigens on its surface. These antigens help the immune system to distinguish between the self-cells, i.e., the cells which are produced by our own body, and the non-self-cells, i.e., the cells that enter the body from outside.

Complete answer:
From the above discussion, it should have been clear to us that antigens are always present within the body. What enters from the outside are foreign cells like bacteria, viruses, and other pathogens which bear their particular and characteristic antigen on their cell surface.
The foreign cells can enter the body through the opening of body cavities like nose, mouth, genital apertures, and through cuts and wounds.
Whenever any foreign cell enters the body, the body’s immune system gets activated and produces antibodies against these antigens, which eventually kills these cells via a series of chemical reactions and processes. The body’s immune system recognizes these cells by the antigens.

Note:
A serious disorder may occur if the immune system fails to recognize between the self and non-self antigens. If the immune system fails to recognize the body’s own antigens, then it starts killing the body’s own cells. This type of disease is known as AutoImmune Diseases. The reason behind these disorders are still a matter of research and genetic factors are believed to be involved in it.
A few autoimmune disorders are:
1. Chronic Anemia: Auto antigens are the RBC.
2. Chronic Hepatitis: Auto antigens are hepatocytes.
3. Myasthenia gravis: Auto antigens are the muscle cells.
4. Type-I diabetes mellitus: IDDM: Insulin Dependent Diabetes Mellitus; either the insulin receptors of the beta-cells of pancreas producing insulin are destroyed.