MAJOR BLOOD GROUPS, ABO(ISBT001) and RH(ISBT004)

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ABO & RH
BLOOD
GROUP

ABO SYSTEM
 Discovered by Karl Landsteiner in 1901
 The ABO system is the most important of all blood groups in transfusion medicine.
 ABO gene is located in “chromosome 9”

 Found on RBCs, lymphocytes, platelets, tissue cells, bone marrow and other
organs.
 Developed in utero 5-6 weeks gestation; full expression occurs between 2-4 years
of age.
Formation of ABO antigens:
ABO Antigen
Gene Glucosyltransferases Immunodominant
Sugar
Antigen
H a-2-L-fucosyltransferase L-fucose H
A a-3-N- acetylgalactosaminyltransferase N-acetyl-D-
galactosamine
A
B A-3-D-galactosyltransferase D-galactose B

ABO Antibodies
Naturally occurring; predominantly IgM
Production initiated at birth
Detectable titers: 3-6 months, peaks at 5-10 years
Blood Group Antibody produced Characteristics
A Anti-B IgM
• Naturally occurring
• React at room
temperature
• Cannot cross placenta
B Anti-A
AB --- ---
O Anti-A
Anti-B
Mostly IgM (some IgG)

Forward Grouping
-Using known sources of commercial anti-sera to detect antigens on an individual’s
RBC
Blood Group Antigen Reaction with Interpretation
Anti-A Anti-B Anti-A,B
A A + - + A
B B - + + B
AB AB + + + AB
O NONE - - - O

Reverse Grouping
-Using reagent cells with known A and B antigens and testing the serum of the patient
for ABO group antibodies
Blood Group Antibody Reaction with Interpretation
A cells B cells
A Anti-B - + A
B Anti-A + - B
AB NONE - - AB
O Anti A & Anti B + + O

ABO Discrepancies
1. Group I Discrepancies
2. Group II Discrepancies
3. Group III Discrepancies
4. Group IV Discrepancies

Group I Discrepancies
-Associated with unexpected reaction in reverse grouping due to weakly reacting or
missing antibodies.
• Newborns
• Patients with Leukemia
• Patients with congenital or acquired agammagloblulinemia or immunodeficiency
disease
• Elderly patients
• Patients with bone marrow or stem cell transplantations

Group II
-Associated with unexpected reactions in the forward grouping due to weakly reacting
or missing antigens.
• Subgroups of A and/or B
• Leukemia
• Hodgkin’s disease
• Acquired B

Group III
-These discrepancies between forward and reverse groupings are caused by protein or
plasma abnormalities and result in rouleaux formation or pseudoagglutination,
attributable to:
• Elevated levels of globin
• Elevated levels of fibrinogen
• Plasma expanders
• Wharton’s Jelly

Group IV
-These discrepancies between forward and reverse groupings are due to
miscellaneous problems and have the following causes:
• Presence of cold reactive autoantibodies
• Unexpected ABO isoagglutinins
• Unexpected non-ABO alloantibodies
• Cis-AB phenomenon

Rh SYSTEM
 Rhesus Blood Group System
 It is the primary cause of HDFN and significant cause of HTR
 RH gene located on short arm of chromosome 1

Rh Antigens
• Rh antigens are highly immunogenic, the D antigen is most potent
• Well developed at birth
• Exposure to 1ml of Rh positive red cells can stimulate Ab production in an Rh
negative person

Rh Antibody
• Most Rh antibodies are IgG, produced through pregnancy and incompatible
transfusions
• Causes HTR and HDFN
Rh Typing
1. Slide typing
• Rapid method; reagent: anti-D antiserum
• Positive test: Agglutination visible within 2 minutes
2. Tube typing
• For differentiating Rh negative (absence of D antigen) from weak D
• Method: INDIRECT ANTIGLOBULIN TEST
Patient RBC + anti-D -> wash RBC -> add AHG

Nomenclature of Rh System
1. Fisher-Race (DCE)
2. Wiener (Rh-Hr)
3. Rosenfield (Alpha-Numeric)
4. International Society of Blood Transfusion (ISBT): Numeric Terminology

Fisher-Race (DCE)
• Most commonly used (i.e. WHO)
• They theorized that Rh antigens are controlled by a complex of 3 sets of genes with
closely linked loci

Wiener (Rh-Hr)
• Rh-Hr Terminology
• Rarely used, but good for describing phenotype
• A single gene at the Rh locus leads at the expression of Rh antigens
• Each gene controls production of an agglutinogen composed of three factors
(antigens)

Rosenfield (Alpha-Numeric)
• Antigens are designated by number

ISBT: NUMERICAL TERMINOLOGY
• To establish a uniform nomenclature that is both a eye and machine-readable
• Adaptation of six-digit number of each identical antigen belonging to a blood group

WEAK D
• Occurs when D is weakly expressed; more common in blacks
4 Mechanisms of weakened expression of D antigen
1. Genetic cause
2. Position effect or C in Trans
3. Partial D or D mosaic
4. Del

MAJOR BLOOD GROUPS, ABO(ISBT001) and RH(ISBT004)

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