The Anti-G Antibody Explains Apparent Anti-C and Anti-D in a dce/dce Individual
The most likely explanation for an individual with dce/dce genotype given dCe/dce blood who develops an antibody response that appears to be both anti-C and anti-D is that the antibody is anti-G.
Understanding the G Antigen and Anti-G Antibody
The G antigen is a composite antigen associated with both C and D antigens of the Rh blood group system. When a person with dce/dce phenotype (lacking both C and D antigens) is exposed to blood containing either C or D antigens, they may produce antibodies against these foreign antigens.
In this specific case:
- The patient has dce/dce genotype (lacking C and D antigens)
- They received dCe/dce blood (containing C antigen but not D)
- They developed antibodies that appear to react with both C and D antigens
Why Anti-G is the Most Likely Explanation
Serological Mimicry: Anti-G antibodies react with both C and D antigens, mimicking the presence of separate anti-C and anti-D antibodies in serological testing.
Genetic Linkage: The G antigen is genetically linked to both C and D antigens, explaining why exposure to blood containing the C antigen could trigger an antibody that appears to react with both C and D.
Impossible Scenario: Since the transfused blood was dCe/dce (containing C but not D), the development of true anti-D would be impossible as there was no exposure to the D antigen.
Ruling Out Other Possibilities
Incorrect reading of agglutination reactions (Option A): While laboratory error is always possible, the consistent pattern of reactivity with both C and D antigens is more likely explained by anti-G than by technical error.
Anti-Cw (Option B): Anti-Cw would not explain reactivity with D-positive cells, and Cw is a low-frequency antigen not typically involved in this pattern of reactivity.
Anti-partial D (Option C): This is not plausible because the patient has dce/dce genotype and therefore has never been exposed to any D antigen variant that could trigger anti-partial D.
Clinical Implications
The distinction between anti-G alone versus separate anti-C and anti-D antibodies has important clinical implications:
- For transfusion: Patients with anti-G require blood that is negative for both C and D antigens
- For pregnant women: Anti-G can cause hemolytic disease of the fetus and newborn (HDFN) if the fetus carries either C or D antigens
Diagnostic Confirmation
To confirm that the antibody is anti-G rather than separate anti-C and anti-D antibodies, specialized adsorption-elution studies would be required:
- Adsorb the patient's serum with D+C- cells to remove anti-D and anti-G
- Elute the antibodies from these cells
- Test the eluate against D-C+ cells
- If the eluate reacts with D-C+ cells, this confirms the presence of anti-G
This case highlights the importance of understanding composite antigens in the Rh system when interpreting antibody identification results in transfusion medicine.