B cells and antibodies are only one arm of the adaptive immune system, specialized in removing foreign material from blood and lymph. The second arm of the adaptive system consists of T cells, which detect and kill cells in the body — “self” cells — that have been invaded by microbes. All viruses invade cells, as do some bacteria. T cells are a major defense against viral infection. There are two types of T cells: CD4 helper cells and CD8 killer cells. Helper cells assist B cells in making antibody, and help CD8 cells mature to kill microbially infected cells. Killer cells are also involved in graft rejection, and in the body's response to cancer.
Keywords: T cells, CD4 cells, CD8 cells, antigen recognition, cancer,