Now, the immune cells can recognize and gobble up the antigens at a faster rate. The next time you are exposed to that particular germ, you will not get sick. The reason you may get a cold every winter is that there are 100 or more different viruses that cause the common cold . Because the white blood cells can remember a germ once they have seen it, vaccines can be developed to prevent infections from developing in the future. When you are vaccinated against a disease, the immune system is given an opportunity to become familiar with a disease organism, such as polio virus, that has been rendered harmless.
Memory cells allow the immune system to destroy an antigen quickly .
The existence of AIDS and cancer illustrates the fact that the immune system can be outsmarted. In the case of AIDS, the HIV virus can hide inside the body's immune cells, thereby rendering useless the body's normal defenses. In the case of cancer, scientists have shown that tumor cells can produce factors that actually coax certain immune cells into helping the tumor grow. By studying AIDS and cancer, scientists have uncovered a great deal of knowledge about how the immune system works. Many of these principles have been used to develop experimental therapies not only for Cancer and AIDS but other diseases as well.