In a patient with a bacterial GI infection, ABO grouping shows a discrepancy. Which finding would explain an acquired B antigen?

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Multiple Choice

In a patient with a bacterial GI infection, ABO grouping shows a discrepancy. Which finding would explain an acquired B antigen?

A bacterial GI infection can modify the A antigen on red cells to a B‑like structure, creating an acquired B antigen. This is detected by using anti-B reagents (anti-B lectin) that bind the B‑like antigen on the patient’s A-type red cells, producing a positive B reaction even though the person is clinically A. To confirm the discrepancy is acquired rather than a true B, secretor studies are done: if the patient is a secretor, ABH antigens appear in secretions according to their genotype, and in an acquired B case the secretions should not show a B antigen. Thus, demonstrating a B antigen on red cells with anti-B lectin and then showing no B antigen in secretions supports an acquired B phenomenon.

A bacterial GI infection can modify the A antigen on red cells to a B‑like structure, creating an acquired B antigen. This is detected by using anti-B reagents (anti-B lectin) that bind the B‑like antigen on the patient’s A-type red cells, producing a positive B reaction even though the person is clinically A. To confirm the discrepancy is acquired rather than a true B, secretor studies are done: if the patient is a secretor, ABH antigens appear in secretions according to their genotype, and in an acquired B case the secretions should not show a B antigen. Thus, demonstrating a B antigen on red cells with anti-B lectin and then showing no B antigen in secretions supports an acquired B phenomenon.

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