Human blood group systems

The International Society of Blood Transfusion (ISBT) currently recognises 29 major blood group systems (including the ABO and Rh systems).^[1] 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 Le^a or Le^b 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".^[2]

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.

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:

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:

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. Normally expressed in a letter or two, with maybe a plus or a minus, these few persons read their blood type in an extensive series of letters in addition to their 'ABO' type designation. (E.g.:AB +ve, O -ve, A1 -ve, etc. are the rare types)

Table

ISBT N°	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 Le^a and Le^b - associated with tissue ABH antigen secretion.	19
008	Duffy	FY	Protein (chemokine receptor). Main antigens Fy^a and Fy^b. 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 Jk^a and Jk^b.	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