Immune Cells and Their Products
The immune system stockpiles a huge arsenal of cells, not only lymphocytes but also cell-devouring phagocytes and their relatives. Some immune cells take on all intruders, whereas others are trained on highly specific targets. To work effectively, most immune cells need the cooperation of their comrades. Sometimes immune cells communicate by direct physical contact, and sometimes they communicate releasing chemical messengers.
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| An antibody is made up of two heavy chains and two light chains. The variable region, which differs from one antibody to the next, allows an antibody to recognize its matching antigen. Credit: NIAID. |
The immune system stores just a few of each kind of the different cells needed to recognize millions of possible enemies. When an antigen first appears, the few immune cells that can respond to it multiply into a full-scale army of cells. After their job is done, the immune cells fade away, leaving sentries behind to watch for future attacks.
All immune cells begin as immature stem cells in the bone marrow. They respond to different cytokines and other chemical signals to grow into specific immune cell types, such as T cells, B cells, or phagocytes. Because stem cells have not yet committed to a particular future, their use presents an interesting possibility for treating some immune system disorders. Researchers currently are investigating if a person’s own stem cells can be used to regenerate damaged immune responses in autoimmune diseases and in immune deficiency disorders, such as HIV infection.
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