So let's begin with gene mutations. So earlier we discussed these self antigens and the fact that our immune cells, white blood cells can distinguish between our healthy cells and non healthy cells by these self antigens. And we said the self antigens must be displayed on special protein complexes on the membrane of the healthy cells. And these protein complexes are known as major histocompatibility complexes or simply MHC. Now, these protein complexes must be coded by some type of section within our DNA. But what happens if there is a mutation within that section of our genetic code?