1. Blood Typing

2. I. ABO System
Each person’s blood is unique from others’ due to marker proteins on the surface of their RBCs

3. In the ABO system, there are 2 possible RBC markers, A and B
If you have type A blood, you produce anti-B antibodies and have type A markers on your RBCs
If you have type B blood, you produce anti-A antibodies and have type B markers on your RBCs
Type O blood means you have no A or B markers and contain both anti-A and anti-B antibodies-because of this they are considered to be a universal donor
If both markers are present, the blood is type AB and is considered to be the universal reciepient because they don’t have any antibodies

5. II. Rh Factor
If you have the Rh factor on your RBCs, then you have Rh-positive(+) blood, and will not make anti-Rh antibodies
If you are Rh-negative (-) blood, you will produce anti-Rh antibodies
Therefore an Rh+ may get blood from either an + or -, but an Rh- can only get Rh- blood.