The immune system is an incredibly important part of any organism. As soon as our immune system fails us, we die.

Since the immune system is so complicated we will break it up into different categories.

In every organism (even in those of the same species), the immune system is unique. However what makes the immune system fascinating is the ability to identify self from non-self amongst all organisms. Even simple multi-cellular organisms such as sponges have the ability to recognise their own cells from foreign cells.

On all cells and viruses have specific antigens. If one of these binds to an antibody or T cell receptor they are called an antigen. These antigens are carbohydrate molecules attached to proteins (glyco-proteins) or lipids (glyco-lipids). Click here for more information on plasma membranes. Antibodies bind to these antigens (click for more info).  

The animation to the right shows a red blood cell. Click the zoom button to see the different antigen markers embedded within the plasma membrane.

Human red blood cells contain a number of antigens. The most commonly know are the A, B and Rh antigen. Cells in your own body contain self-antigens, while foreign cells and materials are called non-self antigens.