Human blood group systems

Human blood group systems

The International Society of Blood Transfusion (ISBT) currently recognises 30 major blood group systems (including the ABO and Rh systems). Thus, in addition to the ABO antigens and Rhesus antigens, many other antigens are expressed on the red blood cell surface membrane. For example, an individual can be AB RhD positive, and at the same time M and N positive (MNS system), K positive (Kell system), and Lea or Leb positive (Lewis system). Many of the blood group systems were named after the patients in whom the corresponding antibodies were initially encountered.

The ISBT definition of a major blood group system is where one or more antigens are "controlled at a single gene locus or by two or more very closely linked homologous genes with little or no observable recombination between them".

Blood Grouping Procedure

Blood is composed of cells suspended in a liquid. The liquid portion is the plasma, from which therapeutic fractions and derivatives are made.

Suspended in the plasma are three types of cells:

  • Red cells carry oxygen
  • White cells fight infection
  • Platelets stop bleeding in injuries

The most common type of grouping is the ABO grouping. Red Blood Cells have a protein coat on their surface which distinguishes them. According to this blood is divided into four groups:

  • A (A oligosaccharide is present)
  • B (B oligosaccharide is present)
  • AB (A and B oligosaccharides are present)
  • O (neither A nor B, only their precursor H oligosaccharide is present)

There are subtypes under this grouping (listed as A1, A2, A1B or A2B…) some of which are quite rare. Apart from this there is a protein which plays an important part in the grouping of blood. This is called the Rh factor. If this is present, the particular blood type is called positive. If it is absent, it is called negative. Thus we have the following broad categories:

  • A1 Negative (A1 -ve)
  • A1 Positive (A1 +ve)
  • A1B Negative (A1B -ve)
  • A1B Positive (A1B +ve)
  • A2 Negative (A2 -ve)
  • A2 Positive (A2 +ve)
  • A2B Negative (A2B -ve)
  • A2B Positive (A2B +ve)
  • B Negative (B -ve)
  • B Positive (B +ve)
  • O Negative (O -ve)
  • O Positive (O +ve)

How is a blood group categorized as rare?

A rare blood type is any blood type that is difficult to find. A blood type is classified as rare when more than 200 donors have to be screened to find one compatible donor with blood of that type. In the "ABO" system, all Blood belongs to one of four major group: A, B, AB, or O. But there are more than two hundred minor blood groups that can complicate Blood transfusions. These are known as rare blood Types. About one person in 1,000 will inherit a rare blood type. Whereas common blood types are expressed in a letter or two, with maybe a plus or a minus, a fewer number of people express their blood type in an extensive series of letters in addition to their 'ABO' type designation. For example, AB +ve, O -ve, and A1 -ve are rare types)


ISBT Common name abbreviation Epitope or carrier, notes Locus
001 ABO ABO Carbohydrate (N-Acetylgalactosamine, galactose). A, B and H antigens mainly elicit IgM antibody reactions, although anti-H is very rare, see the Hh antigen system (Bombay phenotype, ISBT #18). 9
002 MNS MNS GPA / GPB (glycophorins A and B). Main antigens M, N, S, s. 4
003 P P1 Glycolipid. 22
004 Rhesus RH Protein. C, c, D, E, e antigens (there is no "d" antigen; lowercase "d" indicates the absence of D). 1
005 Lutheran LU Protein (member of the immunoglobulin superfamily). Set of 21 antigens. 19
006 Kell KEL Glycoprotein. K1 can cause hemolytic disease of the newborn (anti-Kell), which can be severe. 7
007 Lewis LE Carbohydrate (fucose residue). Main antigens Lea and Leb - associated with tissue ABH antigen secretion. 19
008 Duffy FY Protein (chemokine receptor). Main antigens Fya and Fyb. Individuals lacking Duffy antigens altogether are immune to malaria caused by Plasmodium vivax and Plasmodium knowlesi. 1
009 Kidd JK Protein (urea transporter). Main antigens Jka and Jkb. 1
010 Diego DI Glycoprotein (band 3, AE 1, or anion exchange). Positive blood is found only among East Asians and Native Americans. 17
011 Yt or Cartwright YT Protein (AChE, acetylcholinesterase). 7
012 XG XG Glycoprotein. X
013 Scianna SC Glycoprotein. 1
014 Dombrock DO Glycoprotein (fixed to cell membrane by GPI, or glycosyl-phosphatidyl-inositol). 12
015 Colton CO Aquaporin 1. Main antigens Co(a) and Co(b). 7
016 Landsteiner-Wiener LW Protein (member of the immunoglobulin superfamily). 19
017 Chido/Rodgers CH/RG C4A C4B (complement fractions). 6
018 Hh/Bombay H Carbohydrate (fucose residue). 19
019 Kx XK Glycoprotein. X
020 Gerbich GE GPC / GPD (Glycophorins C and D). 2
021 Cromer CROM Glycoprotein (DAF or CD55, regulates complement fractions C3 and C5, attached to the membrane by GPI). 1
022 Knops KN Glycoprotein (CR1 or CD35, immune complex receptor). 1
023 Indian IN Glycoprotein (CD44 adhesion function?). 11
024 Ok OK Glycoprotein (CD147). 19
025 Raph MER2 Transmembrane glycoprotein. 11
026 JMH JMH Protein (fixed to cell membrane by GPI). 6
027 Ii I Branched (I) / unbranched (i) polysaccharide. 6
028 Globoside P Glycolipid. 3
029 GIL GIL Aquaporin 3. 9


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