Rhesus System Flashcards
Who first described the Rh System?
Levine & Stetson in 1939
How was Rh antigens discovered?
A severe transfusion reaction - woman with post partum haemorrhage after a hydropic stillborn infant - transfused with her husband’s blood - sensitised to red cell antigen that the foetus inherited from the father
How many antigens are in the Rh system?
~40
What are the most common Rh antigens?
•D
•C
•c
•E
•e
Where is the Rh locus?
Chromosome 1
What genes are responsible for the Rh antigens?
•RHD & RHCE genes on chromosome 1
•RH AG gene on chromosome 6 produces the Rh associated glycoprotein - incorporation of the Rh antigen into red cell membrane
What are the relationships between C & c genes and D& d genes
They are antithetical
What does the letter d mean?
Rh D negative
When does erythropoiesis begin?
3 weeks in the embryo
When is the D antigen present in the embryo?
6 weeks
Rh D well developed at birth
What are the characters of the Rh D antigen?
Very antigenic - induce strong immune response (anti D) if introduced into Rh D negative patient
What percentage of Rh D negative in different populations?
•White 15%
•Black 8%
•Asian 1%
•Native American 1%
How should Rh D be tested before transfusion?
Patient’s blood sample is tested with duplicate IgM (saline reactive) monoclonal anti-D grouping reagent
What is used to test Rh D antigen?
2 commercial anti-D antisera - detect presence & absence of Rh D antigen - recheck & highlight anomalies
What stimulates Rh D antibodies?
Pregnancy & transfusion - Rh D negative mothers carrying RH D positive babies
What antibodies are produced after exposure to Rh D antigen?
Small amounts of IgM followed by large amounts of IgG
How do Rh antibodies work?
They don’t fix complement
What are the names of the test used to test for Rh antigens?
Indirect antiglobulin technique aka Indirect Combs Technique - has incomplete antibodies which don’t agglutinate in saline
What’s a disease causes by Rh antigen transfusion?
Haemolytic Disease of the Foetus/Newborn
