Rh Blood Group System

 

Rh Blood Group System

PREPARED BY MR. ABHIJIT DAS

 

Historical Background

• Discovered in 1940 by Karl Landsteiner and Alexander S. Wiener.
• Experiment: Injected Rhesus monkey RBCs into rabbits → rabbit serum agglutinated.
• This led to the identification of the Rh factor (Rh antigen).
• The factor was later named D antigen, the most immunogenic Rh antigen.
• Although the name "Rh" came from the Rhesus monkey, human Rh system is genetically different.

 

Genetic Mapping

• Rh genes are located on chromosome 1.
• Two genes involved:
• RHD gene: Codes for D antigen.
• RHCE gene: Codes for C, c, E, and e antigens.

 

Antigens of the Rh Blood Group System

• Over 50 antigens identified, but 5 are most clinically significant:
• D, C, c, E, e
• D antigen: Most immunogenic → responsible for Rh incompatibility and hemolytic disease of the newborn (HDN).
• Individuals with D antigen: Rh positive
• Individuals without D antigen: Rh negative

 

Variants of Rh Antigen

1. Normal D

• Fully expressed D antigen (all epitopes present).
• Strong agglutination with anti-D.

 

2. Weak D

• D antigen weakly expressed.
• No agglutination on immediate spin.
• Detected by Indirect Antiglobulin Test (IAT).
• Usually does not form anti-D antibodies.

 

3. Partial D

• Some epitopes missing on D antigen.
• May test Rh-positive.
• Important in pregnancy and transfusion.

 

4. Del

·       Extremely low levels of D antigen.

·       Cannot be detected by routine methods (slide/tube/gel).

·       Detected only by adsorption-elution test.

 

Rhesus Antibodies

• Anti-D, anti-C, anti-c, anti-E, anti-e
• Type: IgG
• Formed after exposure (transfusion or pregnancy).
• Can cross the placenta and cause Hemolytic Disease of the Fetus and Newborn (HDFN).