28th May 2023

For most red cell antigens, patients require previous exposure to foreign red cells to develop a haemolytic reaction

For most red cell antigens, patients require previous exposure to foreign red cells to develop a haemolytic reaction. However, for A and B antigens, transfusion of ABO incompatible blood is almost universally fatal, even at first exposure.

Why does ABO mismatched blood cause a haemolytic reaction without prior blood product exposure?

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