In the ABO blood group system, the Bombay phenotype (Oh) lacks both A and B antigens as well as H antigen. Which of the following statements correctly describes the serological consequence of this phenotype?
- A The serum contains anti-A and anti-B antibodies only
- B The serum contains anti-H, anti-A, and anti-B antibodies and is incompatible with all common ABO blood groups ✓
- C The serum contains anti-H antibodies only and is compatible with Group O blood
- D The phenotype is compatible with all blood groups due to absence of surface antigens
Correct answer: B. The serum contains anti-H, anti-A, and anti-B antibodies and is incompatible with all common ABO blood groups
Explanation
The Bombay phenotype lacks the H antigen due to homozygous mutations in the FUT1 gene (fucosyltransferase), so A and B antigens cannot be constructed on erythrocytes. These individuals develop anti-H, anti-A, and anti-B antibodies in their serum. Group O blood still carries the H antigen, making it incompatible with the Bombay phenotype — patients can only safely receive blood from other Bombay phenotype donors. This is a life-threatening situation during emergency transfusion and requires careful documentation.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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