Blood Group

Blood group : is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells. These antigens may be proteins or carbohydrates or glycoproteins depending on the blood group system . Blood antigens controlled by genes that located on the some chromosomes . A total of 30 human blood group systems are now recognized . ( table 1 and figure 1 and 2 )

ISBT Human Blood Group Systems

Number/Name Abbreviation 001 ABO ABO 002 MNS MNS 003 P1 P1 004 Rh RH 005 Lutheran LU 006 Kell KEL 007 Lewis LE 008 Duffy FY 009 Kidd JK 010 Diego DI 011 Cartwright YT 012 XG XG 013 Scianna SC 014 Dombrock DO 015 Colton CO 016 Landsteiner-Wiener LW 017 Chido/Rodgers CH/RG 018 Hh H 019 Kx XK 020 Gerbich GE 021 Cromer CROM 022 Knops KN 023 Indian IN 024 Ok OK 025 Raph RAPH 026 JMH JMH 027 I I 028 P P GIL GIL 30 RhAG RHAG
30 blood group systems 308 blood group antigens 1140 blood group alleles
RBC

ABO – System : Discovery of the ABO system by the Austrian Karl Landsteiner in 1901 marked the beginning of safe blood transfusion . There are 4 major ABO- blood types designated by the antigens present on RBCs : 1- Blood group A : Individuals have the A antigen on the surface of their RBCs , and blood serum containing Anti-B antibodies . Therefore , a group A individual can only receive blood from individuals of groups A or O ( with A being preferable ) and can donate blood to individuals of groups A or AB .

2- Blood group B : Individuals have the B antigen on their surface of their RBCs , and blood serum containing Anti-A antibodies . Therefore , a group B individual can only receive blood from individuals of groups B or O ( with B being preferable ) and can donate blood to individuals of groups B or AB . 3- Blood group AB : Individuals have both A and B antigens on the surface of their RBCs , and their blood serum does not contain any antibodies against either A or B antigen . Therefore , an individual with type AB blood can receive blood from any group ( with AB being preferable ) , but can only donate blood to another group AB individual . (Universal recipient)


4- Blood group O : Individuals do not have either A or B antigens on the surface of their RBCs , but their blood serum contains Anti- A and Anti-B antibodies . Therefore , a group O individual can only receive blood from a group O individual , but they can donate blood to individuals of any ABO blood group ( A , B , O , or AB ) . ( Universal donor ) . ( Table 2 ) .

Table 2 : Blood Transfusion Compatibilities for the ABO Blood Groups

Transfusion can be given to
Transfusion can be accepted from
Antibodies present in serum
Antigens present on RBCs
Blood Group
A , AB
A , O
Anti- B
A galactosamine
A
B , AB
B , O
Anti- A
(B (galactose
B
AB Universal recipient
A , B , AB , O
None
A galactosamine Plus B galactose
AB
O , A , B , AB Universal donor
O
Anti-A plus Anti- B
None
O

Genetics of ABO system

The ABO blood type is controlled by the ABO gene that located on chromosome 9 . This gene responsible for the producing of the A and B antigens and the gene is donated by the letter I . It has 3 alleles IA , IB , IO . The gene encodes a glycosyltransferase enzyme .

People with blood type A have A antigen on the surfaces of their red blood cells and may be of genotype IAIA or IAIO. People with blood type B have B antigen on their red blood cell surfaces and may be of genotype IBIB or IBIO. People with the rare blood type AB have both antigens A and B on their cell surfaces and are genotype IAIB . People with blood type O have neither antigen and are genotype IOIO . ( Table 3 ) Each person has 2 copies of genes coding for their ABO blood group ( one maternal and one paternal in origin ) ( Table 4 )


Table 3 : Genotypes and the Corresponding Phenotypes ( Blood Group Types ) for the ABO Locus in Humans .
Frequency in Population
Phenotype
Activity
Genotype
42%
A
α-3-N-acetyI-D-galactosaminyltransferase IA IA, IA IO
8%
B
α-3-D-galactocyltransferase IB IB, IB IO
3%
AB
Both enzymes
IA IB
47%
O
None
IO IO


Inheritance of Blood Types
These charts show the possible blood type results for offspring.
Mothers's Type
Blood Type
AB
B
A
O
A, B
O, B
O, A
O
O
Fathers' Type
A, B, AB
O, A, B, AB
O, A
O, A
A
A, B, AB
O, B
O, A, B, AB
O, B
B
A, B, AB
A, B, AB
A, B, AB
A, B
AB
Mother's Type
Rh Factor
Rh -
Rh +
Rh +, Rh -
Rh +, Rh +
Rh +
Father's Type
Rh -
Rh +, Rh -
Rh -


Codominance :

The Origin of ABO Antigens :

Figure (2)
The Origin of ABO Antigens :

The Origin of ABO Antigens

The Origin of ABO Antigens

ABO antibodies : Almost all normal healthy individuals about 3-6 months of age have naturally occurring antibodies to the ABO antigens that they lack . Antibodies produced to non self . anti- A and anti- B antibodies are mostly IgM class .( figure 7 )

Blood Transfusions :

The differences in human blood are due to the presence or absence of certain antigens and antibodies , therefore a number of laboratory tests must be completed before blood can be transfused : 1- Blood Typing : The individual blood types of donor and recipient must be determined Using a standard technique , drops of blood are mixed with antisera that contain antibodies against the A and B and RH (D) antigens , and are then observed for the evidence of agglutination . ( Figure 8 and 9 ) . 2- Screening for possible infectious agents that could be transmitted by blood transfusion such as : Human Immunodeficiency Virus ( HIV ) , Hepatitis B Virus (HBV) , Hepatitis C Virus (HCV) and some bacteria and parasites .

Blood Typing Test

This blood is B+


3- Crossmatch ( Compatibility Test ) : The aim of cross matching is to ensure that the blood of a recipient does not contain antibodies that will be able to react with and destroy transfused ( donor ) RBCs .For example : If the donor is A type and the recipient is B type .The RBCs of the type A donor contain antigen A , while the serum of the type B recipient contains anti-A antibodies that can agglutinate donor RBCs ( agglutination : clumping of RBCs when attached to an antibody) Agglutinated RBCs can clog blood vessels and stop circulation in vital organs . (Transfusion reaction :occurs When incompatible blood is transfused , specifically if antibodies in the recipient’s serum cause rapid RBC destruction in the proposed donor ). ( Figure 10 ) .


The primary purpose of the major cross match or compatibility test , is to prevent a possible transfusion reaction . To begin the crossmatch , blood from a donor with the same ABO and Rh type as the recipient is selected . In a test tube , serum from the patient is mixed with RBCs from the donor . If clumping occurs , the blood is not compatible . If clumping does not occur the blood is compatible . ( Figure 11 and 12 ) .
Compatible
Not compatible

Table (4)

Blood Transfusions :

RH- System

RH blood types ( Rhesus factor ) were discovered in 1940 by Karl Landsteiner and Alexander Wiener . Like the ABO system , the RH system is defined on the basis of antigens that are present on erythrocyte surfaces . Rh factor is a protein found on most peoples RBCs .

Genetics of RH- System : The RH locus is located on the chromosome 1 . It contains two closely linked genes RHD and RHCE . RH D gene encodes D antigen( transmembrane proteins ) RHCE gene encodes CE antigens . Figure 14 RH antigens are transmembrane proteins with loops exposed at the surface of red blood cells .

Person with the DD or Dd genotype have the RH antigen ( D antigen ) on their erythrocytes and are termed RH-Positive . person with genotype dd are RH-Negative and do not have the RH antigen . ( Figure 15 ) Frequency in population RH- Positive 85% , RH- Negative 15% .



Importance of RH system :
RH D antigen is the most immunogenic red cell antigen after A and B antigen . RH D antibody can cause hemolytic transfusion reactions and hemolytic disease of newborn or erythroblastosis fetalis .
Anti- RH antibodies : Anti RH antibodies of the system are not normaly present in the system but can be produced if an individual with RH- is exposed to RH+ antigen usually through pregnancy or incompatible blood transfusion .


In the First Pregnancy with RH Positive fetus : RH+ antigens from the developing fetus can enter the mothers blood during delivery . ( Figure 16 ) After birth or abortion : The mother will produce anti RH antibodies In next Pregnancy with RH Positive baby : Mother anti RH antibodies IgG will cross the placenta and damage fetal red blood cells and cause disease called Hemolytic Disease of Newborn .

RH Hemolytic Disease of Newborn :

Preventing Hemolytic Disease of Newborn (HDN): RH negative mother is givin injections of anti-RH D antibodies D gamma globulin called ( Rhogam ) around the 28 th week of pregnancy and again with in 72 hours after the delivery of the RH Positive baby . This must be done for the first and all subsequent pregnancies . The injected antibodies quickly agglutinate any fetal red blood cells as they enter the mother’s blood before they stimulate production of anti- RH antibodies .

Inheritance of ABO and RH blood groups :