ABO typing of red cells and plasma/serum

ABO typeGeneaRBC groupingb (forward or antigen type) Serum groupingc (back type)
A1 ++++000+0
A2 d +++0++/0+0
Oe +000++++0
Oh f (Bombay)0 (hh)+000+++
  • a Inheritance of at least one functional H gene (FUT1) and ABO gene.

  • b Testing for ABO antigens on red cells with monoclonal anti-A and anti-B. H antigen is detected with the Ulex europaeus lectin (UEA-1).

  • c Testing of plasma/serum against red cells of a known ABO type to detect anti-A, anti-B, or anti-H.

  • d A2 is the most common weak A phenotype, is characterized by increased H antigen levels, and may possess anti-A1. A2 and other weak A red cells do not agglutinate with the anti-A lectin of Dolichos biflorus.

  • e Group O is due to the homozygous inheritance of ABO amorph alleles.

  • f Bombay Oh is a rare autosomal-recessive phenotype due to amorph FUT1 (hh) and FUT2/Secretor (se/se). Bombay individuals lack H, A, and B antigens and possess hemolytic anti-A, anti-B, and anti-H.