However, natural killer cells are the exception. They are unique because they do not require the presence of the major histocompatibility complex on the membrane of that particular abnormal cell. Interestingly, some infected or cancer cells sometimes are missing the MHC entirely from their membrane which makes them virtually invisible to all the other white blood cells of our body except these natural killer cells. So let's take a look at the following diagram and examine exactly what the mechanism is by which the natural killer cell detects as well as destroys our cancer cells. So when cells display little or no MHC proteins on their membrane, then that triggers the natural killer cell to basically approach and bind onto that cancer cell. So in this particular case, we have a normal cell, a normal cell and a normal cell that contains a normal antigen, a normal cell antigen shown in green, as well as the MHC class one complex shown in brown.