The immune system is a group of cells, tissues and organs that function to recognize and destroy pathogenic bacteria and viruses. It is the body's main defense against foreign antigens and works to keep humans healthy everyday.
The immune system is comprised of many different cells. One of the main immune cells in the human body is the white blood cell, or leukocyte. There are two basic forms of white blood cells. These include the phagocytes, which digest and destroy invading pathogens, and the lymphocytes, which tag and recognize invading pathogens. The lymphocytes also help the human body produce memory cells that quickly recognize and destroy pathogens that the body has previously encountered. The immune system is working at all times to destroy pathogens and keep the human body healthy.