So virtually all cells in our body, all white blood cells, require these major histocompatibility complexes to actually interact with one another and to detect these abnormal cells. But the very unique thing about natural killer cells which, by the way, are part of the innate immunity of our immune system, the very unique thing about these natural killer cells is that they don't actually need the major histocompatibility complex to actually find what our abnormal cell actually is. Unlike most other cells of our body, including cytotoxic T cells, the other white blood cell that destroys cancer cells. And this is a good thing because sometimes the cancer cells or infected cells lose the ability to create the MHC class One or the MHC class two complex. And that means it no longer contains these complexes on their membrane. And that makes it virtually invisible to all the cells of our body, all the white blood cells that require the MHC class One or class Two to actually detect those cells.