Immunology: The study of the immune system, the bodies response to infection and other foreign substances.
In response to foreign substances, the body makes antibodies, special proteins, which attack these substances (such as bacteria) and prepare them for attachment to other cells in the body which destroy the foreign substance.
This is the main system that the body has for fighting infections.
Antibodies are very elegant and precise in their formation and specificity. That is, in general, an antibody is made specifically for one antigen. An antibody made to attach a Staph bacteria will not attack a Strep bacteria.
This specificity can be very useful in medicine. For example, scientists have made an antibody to one of the cell surface proteins on special types of breast cancer. This antibody only attacks this particular breast cancer cell and helps the body destroy it.
Scientists have created antibodies to perform a wide range of functions both in the body, as well as in the test tube, to help identify diseases. Imagine an antiboy that is linked to a red dye, which attaches to prostate cancer cells. On a slide of a piece of prostate, if there are cancer cells, the antibody will attach to them, and the red dye will light up. This makes detection of the cancer cells much easier.