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ABO Blood Grouping: Principle and Biochemistry

ABO blood grouping is critically linked to several important determinants, which are considered precursors to the formation of detectable, testable antigen. The main precursor is the H antigen. Creation of specific A and B antigens is determined by the addition of specific glycosyltransferases (enzymes) that add specific sugars to the H antigen.
These added sugars result in the precursor conversion to a detectable RBC antigen.
H Gene (Hh or HH)
The antigenic precursor on which A and B antigens are made. Without the H antigen, individuals cannot demonstrate the expression of A or B antigenic determinants on the RBC membrane surface.
GeneGlycosyltransferaseImmunodominant Sugar
Resulting Antigen
Hα-2-L-fucosyltransferase L-fucose
Aα-3-N-acetylgalactosaminyltransferaseN-acetyl-D-galactosamine A