About Immunity
The immune system is what protects your body from diseases and infections. It's the bodily system that produces the immune response to defend your body from foreign substances, cells, and tissues. The immune system includes various parts of the body including the thymus, spleen, lymph nodes, special deposits of lymphoid tissue (such as those in the gastrointestinal tract and bone marrow), macrophages, lymphocytes including the B cells and T cells, and antibodies.
Many cells and organs work together to protect the body. White blood cells, also called leukocytes, play an important role in the immune system.
Some types of white blood cells, called phagocytes, chew up invading organisms. Others, called lymphocytes, help the body remember the invaders and destroy them.
One type of phagocyte is the neutrophil, which fights bacteria. When someone might have bacterial infection, doctors can order a blood test to see if it caused the body to have lots of neutrophils. Other types of phagocytes do their own jobs to make sure that the body responds to invaders..........