Rh System Flashcards
What genes are responsible for Rh antigen expression?
The RhD and RhCE genes on chromosome 1. RhD encodes the D antigen, and RhCE can produce C, c, E, or e antigens via alternative splicing.
What does it mean if someone is RhD negative?
They lack the RhD gene product entirely — no D protein is expressed.
Which Rh antigens are clinically significant?
D, C, c, E, and e.
What is “weak D”?
A quantitative variant with reduced D antigen density on RBCs.
Which is the most immunogenic Rh antigen?
The D antigen.
What is the most common Rh genotype in the population?
DCe/dce (R1r) — seen in about 33% of the population.
What does a phenotype of R1R2 indicate in Rh typing?
Presence of D, C, c, E, and e antigens.
Why are Rh antibodies considered clinically significant?
They can cause hemolytic disease of the fetus and newborn (HDFN) and transfusion reactions. They’re typically IgG and react at 37°C.
What is “partial D”?
A qualitative variant where part of the D antigen is missing, potentially causing alloanti-D formation after exposure.
Should weak D individuals receive RhD positive or negative blood?
Generally, they are considered RhD positive if donors, but may be treated as RhD negative when recipients to avoid alloimmunization.
What must be done if a clinically significant antibody is detected during screening?
Only antigen-negative blood units should be selected for transfusion.
What testing is done for patients with a history of antibodies that are now undetectable?
Manual crossmatch is required.
How do Rh antibodies usually develop (excluding ABO)?
Through alloimmunization — via transfusion or pregnancy exposure to Rh-positive blood in Rh-negative individuals.
What type of hemolysis do Rh antibodies cause?
Extravascular hemolysis, which may be immediate or delayed.
