This recognition and destruction is performed by cells in the circulatory and the lymphatic systems. These cells are so featureless that there is no way to determine what type of blood cell they will ultimately become. These cells are then released into the blood stream and are carried to all parts of the body. Memory cells, as the name implies, remember specific foreign cells or chemicals to which they have been exposed, and react immediately when they are next exposed to those compounds. Drugs which effect the memory cells stimulate immunity only to one disease or antigen.
Vaccines are an example of drugs which effect memory cells.
Remarkably, since the discovery of penicillin, our scientists, in search of drugs against infectious disease, have looked only for chemicals which kill bacteria or viruses. Finally, they are coming to realize that it is possible to boost the immune system, which can then fight naturally against infectious agents, without the drawbacks of antibiotic therapy. While immune stimulants cannot replace antibiotics in some cases, they have proven far superior in others. In Asia, this plant is sold as dried slices of root, six to twelve inch long. Research has shown that this root and its extracts are powerful stimulators of the immune system.