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Explain the basis of ABO and Rh incompatibilities?

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Kyle L. | Science & pre-health tutor. Prior university teaching experienceScience & pre-health tutor. Prior univer...
5.0 5.0 (3 lesson ratings) (3)
In an attempt to expand on Naina's answer the A,B,O blood time is determined by the presence or absence of specific carbohydrates (referred to above as surface antigens) on the erythrocytes, or red blood cells that are recognized by the individuals immune system. For instance, let us say that Type A is characterized by circle carbohydrates and Type B is represented by triangles. The immune system of a type A patient would recognize the triangle antigens as foreign and therefore elicit an immune/inflammatory response. For this reason Type B blood is incompatible for a Type A patient. 
Furthermore, AB blood has the presence of both surface antigens so there is no immune response upon transfusion of Type A, B, AB or O blood. O in turn is completely devoid of these surface antigens and is therefore the universal donor. The Rh factor is an additional category represented by + or -. O- is truly the universal donor when you take into account Rh factor
Naina B. | Naina, a versatile tutorNaina, a versatile tutor
4.8 4.8 (155 lesson ratings) (155)
Hi Ryan,
Rh is cell surface antigen on RBCs. A, B, and O are different blood types based on presence of these small molecules. Incompatibility occurs when the blood containing one group gets exposed to blood with different group, as is the case with blood transfusion. For Rh factor, sometimes a fetus in uterus can be Rh positive but mother may not be or vice versa. This causes Rh incompatibility.
Hope this helps.