Appendix 02. Four major groups


Four major groups of A, B, AB, and O are defined by the presence or absence of 2 antigens (A and B) on RBCs, and of the antibodies against these antigens in sera. Blood group A individuals have A antigens on RBCs and anti-B antibodies in serum. Similarly, blood group B individuals have B antigens on RBCs and anti-A antibodies in serum. Blood group AB individuals have both A and B antigens on RBCs and neither anti-A nor anti-B antibodies in serum. On the contrary, blood group O individuals have neither A antigens nor B antigens, but possess both anti-A and anti-B antibodies in serum. The observed rule that individuals have the antibodies against A or B antigens if they do not express A or B antigens on RBCs, respectively, has been named the Landsteiner’s Law. The presence or absence of A or B antigens can be detected by the RBC agglutination reaction, using the anti-A or anti-B reagents (the forward test). The presence or absence of anti-A or anti-B antibodies in serum can be detected by the RBC agglutination reaction, using the reference A1 and B RBCs (the reverse test).  These tests are routinely used to determine ABO blood type at any hospital.

Appendix 03. Genetic basis of ABO blood grouping

Appendix 01.Discovery of the ABO blood group system 

01. ABO Blood Group System


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