So remember, we have three different types of lymphocytes. We not only have B lymphocytes and T lymphocytes but we also have natural killer cells which basically looks something like this. Now, natural killer cells are those cells that essentially bind to antigens on other cells and they can either kill off infected cells or they can kill off cancer cells. So we see that natural killer cells seek out and destroy infected cells that have been infected by, let's say, some type of virus and they also kill off cancer cells. Now, what about B lymphocytes and T lymphocytes? Let's begin with B lymphocytes.