And this is what we call a blood type O. So such an individual lacks both antigens and their red blood cells on their red blood cells. And so the immune system produces antibodies against antigen A as well as against antigen B. So now that we discuss the four different types of blood types, blood groups, let's discuss the process of blood transfusion. So it is actually possible to transfer blood from one individual to a different individual. However, one must keep in mind that certain blood types cannot be mixed and that's because if they are mixed they will agglutinate.