Our immune systems are the principal line of defense against infections and some cancerous growths.
Antigens are any of a variety of substances that the body 'sees' as foreign.
In response to the presentation of an antigen, the immune system kicks into gear. When special receptors on the surface of immune cells called T cells bind to antigens, the cells are activated to both multiply and differentiate into several types of more specialized T cells. These cells then carry out a variety of defensive functions. There are advantages to using these artificial cells, Sadelain points out. The experimental cells are very stable and relatively easy to handle.