T Cells and Cancer
T cells, a type of white blood cell produced in the bone marrow, are the main soldiers of the immune system. Killer T cells (also known as CD8 cells) patrol the body looking for invaders such as viruses and abnormal cells that could turn into cancer. After mounting their attack, some T cells evolve into memory cells that can more quickly recognize and respond to the same problem in the future. But cancer cells are sneaky: They can sometimes hide from the immune system or turn off its defenses, allowing the cancer to grow out of control.