Paper I — 2022 October (Supplementary) (2010 Scheme) — Q6
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Paper I
2022 October (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Hapten
Q62 marksShort Notes
Answer
A hapten is a small molecule that is antigenic (can react specifically with pre-formed antibody) but not immunogenic by itself — it cannot provoke an antibody response on its own because it is too small to be recognized by helper T cells. It becomes immunogenic only after conjugating to a larger carrier protein, which supplies the T-cell epitopes needed for a full response; the hapten itself then behaves as the antigenic determinant (epitope) that the resulting antibody recognizes.
Examples: Penicillin — its breakdown product (penicilloyl group) binds host protein, forming the hapten-carrier complex responsible for penicillin allergy; urushiol (poison ivy, contact dermatitis); some drug-induced immune hemolytic anemias.
