Question

question 20

a patient has anti-f antibody. which of the following units should be safe to transfuse?

• r
• r1r
• r0ry
• r1r2

Explanation:

Define the f antigen and anti-f antibody

Using the Rh Blood Group System knowledge point
The f antigen (\(ce\)) is a compound antigen in the Rh blood group system. It is expressed only when both the \(c\) and \(e\) genes are inherited on the same chromosome (in the cis position). A patient with anti-f antibody will react with any red blood cell unit that carries the f antigen. Therefore, a safe transfusion unit must be f-antigen negative, meaning it does not possess both \(c\) and \(e\) on the same haplotype (cis).

Translate Wiener genotypes to Fisher-Race haplotypes

Using the Wiener Nomenclature knowledge point
To evaluate the options, we translate each Wiener genotype into its corresponding Fisher-Race haplotypes:

• \(r''r\): \(dC^we / dce\) or \(dcE / dce\). Since \(r\) represents \(dce\), this genotype contains the \(dce\) haplotype, which carries both \(c\) and \(e\) in cis. Thus, it is f-positive.
• \(R_1r\): \(DCe / dce\). This genotype contains the \(r\) (\(dce\)) haplotype, which carries both \(c\) and \(e\) in cis. Thus, it is f-positive.
• \(R_0r_y\): \(Dce / dCE\). This genotype contains the \(R_0\) (\(Dce\)) haplotype, which carries both \(c\) and \(e\) in cis. Thus, it is f-positive.
• \(R_1R_2\): \(DCe / DcE\). Neither haplotype (\(DCe\) or \(DcE\)) contains both \(c\) and \(e\) on the same chromosome. Therefore, this genotype is f-negative.

Determine the safe unit for transfusion

Using the Rh Blood Group System and Wiener Nomenclature knowledge points
Since the patient has anti-f, they require f-antigen negative blood. Among the choices, only \(R_1R_2\) (\(DCe/DcE\)) lacks the \(ce\) (cis) combination on both chromosomes, making it f-negative and safe to transfuse.

Answer:

• (A) r"r
• (B) R1r
• (C) R0ry
• (D) R1R2 (Correct answer)