We have killer T cells, we have suppressor T cells, we have helper T cells. We also have memory T cells. And we'll discuss these different types of T lymphocytes in the next several lectures. Now, the main function of these T lymphocytes is to actually recognize different types of pathogens, different types of bacterial cells and infected cells by using the antigens found on the surface of those infected and bacterial cells. So these cells have a special protein on their membrane that can recognize foreign antigens and kill off those pathogens. Now, let's move on to the antibody mediated immunity.