Mimi

IMMUNE TROOPS! MOVE IN!
by Shauna Hutton
Your body has a very special system that protects you from illness and disease. It’s called the immune system and it knows when there is something insideyour body that should not be there. All the cells in your body have a way to tell the immune system, “I belong here. I’m not going to do any harm.” And so the immune system leaves those cells alone.Think about the cells in your body wearing name tags that say “self”. Anything with a “self” name tag is a good guy. But things like bacteria, viruses, and parasites wear name tags that say “nonself”.When the immune system sees a “nonself” name tag, it jumps into action and attacks those foreign invaders. Any foreign substance in your body that makes the immune system attack it, is called anantigen. These antigen invaders can be pollen from the air, a virus, or certain types of bacteria.

There are many different kinds of immune cells helping to keep you from getting sick. They can be groupedinto phagocytes (pronounced fag-uh-sahyt) and lymphocytes (pronounced lim-fuh-sahyt). Phagocytes are a type of white blood cell, and one of their jobs is to gobble up and digest antigens. They arealways swimming around in your blood stream, always on the lookout for antigens. And when they see one, GULP! Lymphocytes are also white blood cells and the main types are B cells, T helper cells, and Tkiller cells. Many antigens can be very sneaky (like viruses) and can hide from phagocytes, so it’s the job of the lymphocytes to find them and get rid of them.

B cells secrete (produce)substances, called antibodies, which stick to the antigen. When that happens, it alerts the T helper cells to come over and either: 1. help the B cells destroy the antigen, or 2. call the phagocytes or Tkiller cells to move in for the kill T killer cells are really good at finding and killing cells that have been infected by a virus. Once a B cell or T cell attacks an antigen, they create cells to...