A 19-year-old presents with fever, posterior cervical lymphadenopathy, pharyngitis and splenomegaly. Peripheral smear shows atypical lymphocytes. The heterophile antibody detected in this illness is directed against which antigen?
- A Sheep red blood cell antigens ✓
- B EBV viral capsid antigen
- C CD21 receptor on B cells
- D EBV nuclear antigen core complex
Correct answer: A. Sheep red blood cell antigens
Explanation
In infectious mononucleosis, activated polyclonal A cells produce nonspecific IgM antibodies that agglutinate sheep and horse red blood cells; this forms the basis of the Paul-Bunnell monospot test. These heterophile antibodies are not directed against any Epstein-Barr virus protein. CD21 is the cellular receptor used by EBV to enter A cells, and anti-VCA and anti-EBNA antibodies are separate specific markers measured when the monospot test is negative.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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