Blue = clinical significance | Red = tips for your test

Previously on Blood Antigens…. We talked about a person with blood type A specifically and how the immune system plays a role in making sure to attack foreign antigens if they do enter the body.

Well why is it so important that the immune system make sure that no other blood types are able to enter? It all goes back to the immune system setting up a line of defense to make sure that nothing that is not part of the “self” can enter. Because if there was no line of defense set up, then bad things like bacteria could enter and wreak havoc all the time. Granted, bacteria still enter but most of the time our immune system is robust enough to handle the bacteria. Let’s take a look at a disease where the immune system is not robust enough like HIV. In HIV, the virus itself attacks the immune system and so people with HIV are always battling different types of infections. The immune system pretty much gets beat up by HIV and is not able do its job properly so this is why people with the disease have overwhelming amounts of infections and need to be on antibiotics prophylactically (prophylaxis means to prevent disease so prophylactic antibiotics are antibiotics given to patients even without any symptoms because it will prevent future infections).

Going back to the blood antigens let’s think about someone with blood type O. Now take a second to think about what kinds of antigens and antibodies are present in these patients. Blood type O has no antigens on it so what kind of antibodies does a person with blood type O have? A person with blood type O will have antibodies against A and B. What about blood type AB? These folks have both A and B antigens on the surface of red blood cells. So what kind of antibodies are present in the blood? None! Now lets apply this to real life. If I come into the hospital and I needed a blood transfusion immediately and no one knew what blood type I was, which blood could they transfuse me with and not have to worry about my immune system trying to attack the blood? Before you answer, it is important to know that a blood transfusion just has the red blood cells in it and does not contain all of the antibodies that are in the serum. So a person with blood type O which means a red blood cell with NO antigen on it can be given to anyone as a blood transfusion. This makes sense because a person with blood type A has A antibodies already made but if blood type O was introduced, those antibodies would not be able to attack the O red blood cells because there is no antigen present on the O red blood cell.

Make sure you are able to understand why blood type O is considered the universal donor and blood type AB is the universal recipient.