Question:
Which of the following is an example of Heterophile antigen?
Which of the following is an example of Heterophile antigen?
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The heterophile antibody test (Paul-Bunnell test) used to diagnose infectious mononucleosis in humans relies on the cross-reactivity of human serum antibodies with sheep red blood cells containing the Forssman antigen.
Updated On: Aug 24, 2026
- Forsmann antigen
- Isoantigen
- LPS
- Hapten
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
A heterophile antigen is an antigen that is shared by completely unrelated species of animals, plants, and microorganisms.
Due to this structural similarity, antibodies produced against a heterophile antigen in one species can cross-react with cells or tissues of another species.
Step 2: Detailed Explanation:
The classic and most well-studied example of a heterophile antigen is the Forssman antigen.
It is lipopolysaccharide-protein complex widely distributed across many species, including sheep red blood cells, guinea pig tissues, horse tissues, and various bacteria (such as Pneumococci).
However, it is absent in rabbits, pigs, humans, and cattle.
The other options represent different immunological components:
- Isoantigen: Antigens present in some but not all members of the same species (e.g., blood group antigens).
- LPS (Lipopolysaccharide): A major structural component of the outer membrane of Gram-negative bacteria.
- Hapten: A small molecule that can elicit an immune response only when conjugated to a larger carrier protein.
Therefore, the Forssman antigen is a prime example of a heterophile antigen.
Step 3: Final Answer
The correct option is (A).
A heterophile antigen is an antigen that is shared by completely unrelated species of animals, plants, and microorganisms.
Due to this structural similarity, antibodies produced against a heterophile antigen in one species can cross-react with cells or tissues of another species.
Step 2: Detailed Explanation:
The classic and most well-studied example of a heterophile antigen is the Forssman antigen.
It is lipopolysaccharide-protein complex widely distributed across many species, including sheep red blood cells, guinea pig tissues, horse tissues, and various bacteria (such as Pneumococci).
However, it is absent in rabbits, pigs, humans, and cattle.
The other options represent different immunological components:
- Isoantigen: Antigens present in some but not all members of the same species (e.g., blood group antigens).
- LPS (Lipopolysaccharide): A major structural component of the outer membrane of Gram-negative bacteria.
- Hapten: A small molecule that can elicit an immune response only when conjugated to a larger carrier protein.
Therefore, the Forssman antigen is a prime example of a heterophile antigen.
Step 3: Final Answer
The correct option is (A).
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