And finally, blood type O means we have neither antigen A or antigen B on the red blood cell of the membrane of our red blood cell. Now, the next question is what exactly is the big deal? And what's the relationship between these groups and our immune system? Well, let's begin with blood type A. So, in an individual that has blood type A, what that means is on chromosome nine of that individual, they have a gene that codes for antigen A. And that means all the red blood cells will contain this particular glycoprotein antigen A.