The immune system constantly monitors all the substances normally found in the body. Any new substance that is not recognized by the immune system raises an alarm, causing the immune system to see it as “foreign or non-self” and attack it.1 The immune response can destroy anything containing the foreign substance, such as germs or cancer cells.1
The immune system can be activated by many “non-self” substances or antigens.3 For example, the proteins on the surfaces of bacteria, fungi and viruses are all antigens, and when the antigens bind to special receptors on the defense cells, a series of cell processes is started. Then the immune system can recall stored “memories” in order to more quickly be ready to defend against known pathogens.3
The body’s own cells also have surface proteins. However, the immune system does not attack them, because it has already learned at an earlier stage to identify specifically these cell proteins as “self.”3
The immune system can be activated by many “non-self” substances or antigens.3 For example, the proteins on the surfaces of bacteria, fungi and viruses are all antigens, and when the antigens bind to special receptors on the defense cells, a series of cell processes is started. Then the immune system can recall stored “memories” in order to more quickly be ready to defend against known pathogens.3
The body’s own cells also have surface proteins. However, the immune system does not attack them, because it has already learned at an earlier stage to identify specifically these cell proteins as “self.”3
