Learning Objectives :
 Describe function of agglutinogen and agglutinin in relation to blood group
 Describe antigen and antibody of ABO system
 Describe mechanism that inherit the ABO system
 List phenotype and genotype of possible ABO types.
 Describe antigen and antibody of Rh system.
 Explain universal donor and universal recipient
 Describe transfusion reaction related to ABO and Rh system
 Describe erythroblastosis fetalis.
Lecture outline:
Membrane of red blood cells contains blood group antigens- agglutinogens
Blood Types:
ABO – most important
Rh – Also important
Less important blood groups include MNSs , Lutheran , kell , kidd etc.
ABO blood group system:
4 types of blood groups in this system:
A – has antigen A
B – has antigen B
AB – has antigen AB
O – has no antigen
All these types contains H antigen on cell surface
A type – Acetylgalactosamine
B type - Galactose
AB type – Both
O type - Only H antigen
Anti bodies against RBC antigen are called as agglutinins
No antibodies development against antigen present in own cells
2 types:
IgM and IgG
Inheritance of ABO blood groups occurs via mendelian transmission
When the blood types of parents is known then the possible genotype of the offspring can
be predicted.
Most common blood type is O (47%) followed by A (41 %) , B (9%) AB ( 3%)
Rh blood group system:
Found only in RBC ( ABO also found in other tissues like kidneys etc)
Three types C , D , E – most important is D
Rh positive called when D antigen is present
99% Asians are Rh positive
Rh negative person can produce anti –D anti body when exposed to antigen D , this anti
body will not develop with exposure to antigen D
Transfusion reaction:
Calls from the donor react with recipient antibody
Incompatibility makes clumps / agglutinates
Antibodies have several sites for binding with the antigens
IgM has 10 sites ( pentamer)
IgG has 2 sites ( monomer) This is the reason why IgG can cross the placenta whereas
IgM cannot as it has got a large size
Antibodies from donors donot cause problem as they are diluted in the recipient’s blood
Transfusion reaction can be mild ranging from fever ,tachycardia to more severe forms
consisting of rash, shortness of breath ,jaundice, hemolysis, angioedema etc…
Ab type is regarded as universal recipients --- as they have no anti body against both A
or B antigens
O type is regarded as universal donors.
Both types do need a cross match
Erythroblastosis fetalis: Also called as HDN (hemolytic disease of
newborn)

A severe hemolytic disease of a fetus or newborn infant caused by the production
of maternal antibodies against the fetal red blood cells, usually involving Rh
incompatibility between the mother and fetus
Common causes for HDN
 Rh system antibodies
 ABO system antibodies
Uncommon causes
 Kell system antibodies
Rare causes
 Duffy system antibodies
 MNS and s system antibodies
No occurrence in HDN
 Lewis system antibodies
 P system antibodies
Rh incompatibility:
 Rh incompatibility is a condition which develops when there is a difference in Rh
blood type between that of the pregnant mother (Rh negative) and that of the fetus
(Rh positive).
 After the initial exposure to a foreign antigen, the maternal immune system
produces antibodies of the immunoglobulin M (IgM) isotype that do not cross the
placenta, and later it produces antibodies of the IgG isotype that traverse the
placental barrier.
Before birth, these antibodies causes destruction of RBC leading to:
 Anemia
 heart failure
 fetal death
After birth ,the destruction of RBC by the same antibodies leads to:
 Anemia
 Heart failure
 Build up of bilirubin
 Kernicterus
 Severe retardation
Problems occurring in the newborn:
 Anemia
 heart failure
 erythroblastosis
 General edema
Called hydrops fetalis and erythroblastosis fetalis
 Kernicterus
 severe retardation