So even though the immune system as a whole functions to detect and destroy these cancer cells two particularly important types of white blood cells involved in the process of destroying infected and cancer cells are natural killer cells as well as cytotoxic T cells also known as killer T cells. And these are two different types of white blood cells. So let's begin with natural killer cells. So natural killer cells are specialized lymphocytes and they have granules that carry digestive enzymes as we'll see in just a moment. And these granules, these vesicles play an important role in destroying those cancer cells. Now let's recall the important points.