Your immune system is what keeps your body healthy. It is a network of cells, tissue, and organs that keep out the pathogens. When the immune system fails to keep the diseases or viruses out, your immune system rushes into action to seek and destroy the tiny little organism.
When their is a foreign object that is harmful to the body, it is known as an antigen. Antigens cause an immune response which tells the white blood cells to start producing antibodies. Antibodies are little proteins that bind to the antigen. When the antibody binds to the antigen, it disables the chemical action in the antigen.
Immunology is a very cool science to study. It is all about how your immune system and how your body can become immune after having a certain disease or virus. When your body is immune to something, it means that your body has learned how to quickly fight off a disease through past experience with the disease.
There are diseases that cause the immune system to attack the healthy cells of the body. Autoimmune diseases do one of two things. It can either slow down the immune system which keeps it from protecting our bodies from dangerous pathogens. Or the autoimmune disease can cause the immune system to increase its activity and destroy the body's own healthy cells.