Now the immune system, because these are self antigens, that means the immune system will not produce any antibodies against the antigen A glycoprotein. But because the red blood cells of blood type A individual do not have antigen B proteins, what that means our immune system will begin producing antibodies against that particular antigen B. And so if that individual with blood type A ever receives blood type B, for example, the red blood cells of the blood type B individual will be destroyed as a result of the presence of those antibodies against antigen B. And we'll see exactly what that means in just a moment. So this is our red blood cell of a person that has blood type A. So blood type A individual contains red blood cells that contain a membrane protein we call antigen A.