ABO blood group compatibility (universal donor/recipient)
Core concept
- ABO antigens are carbohydrate epitopes on RBC (and endothelial) surfaces, built by glycosyltransferases on the H antigen
- A = N-acetylgalactosamine; B = galactose; O = no transferase (H antigen only)
- *Antibodies are NATURALLY OCCURRING, IgM, and present without prior exposure* (Landsteiner's law)
- From environmental/gut bacterial carbohydrate cross-reactivity, appear ~3-6 months of age
- -> IgM, complement-fixing -> intravascular haemolysis on incompatible transfusion
- Rhesus (D) antibodies are the opposite: IgG, immune (require sensitisation), extravascular haemolysis, cross the placenta
3 more sections, plus exam facts
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