A small molecule that can trigger an immune response when attached to a larger protein molecule in the body.
From Greek 'haptein' meaning 'to fasten' or 'to grasp,' coined in the early 20th century by immunologists to describe molecules that 'grasp' or bind to proteins. The term reflects how these molecules latch onto larger carriers.
Haptens are why some people are allergic to penicillin—the antibiotic is too small to trigger an immune response by itself, but it binds to body proteins and tricks your immune system into attacking it. This discovery revolutionized how we understand drug allergies!
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