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. So this involves not T lymphocytes but B lymphocytes or B cells. And we also have different types of B cells. We have plasma B cells and we have memory B cells and we'll discuss their unique individual function in the next several lectures.