So their red blood cells will contain that antigen D. On the other hand, an individual that is essentially RH negative does not have the gene on their DNA and so will not code and create that protein and will not have antigen D on the membrane of their red blood cells. So in this particular diagram, we're describing a person that is blood type A and which is RH negative. Now, unlike the Abo blood group, an RH negative individual will not normally produce the antibody against antigen D. However, if they are actually ever exposed to that antigen D, only then will their immune system begin producing the antibody against antigen D. And to see what we mean, let's once again look at the following diagram. Let's suppose we have an RH negative individual that is that has the blood group A, blood type A. What that means is they will have antigen A on their membrane and will not have antigen B. And it also means that because they don't have antigen B, their immune system will or readily produce antibodies against antigen B and those antibodies will circulate in the blood.