Haptens

Haptens (also partial , incomplete or incomplete antigen ; from Greek ἅπτειν haptein : 'to grasp something, to grasp') are molecules or ions, such as B. atrazine , digoxigenin or nickel ions, which do not represent full-fledged antigens in isolation; d. that is, they are unable to provoke an immune response on their own . This is possible with these substances when they bind to an endogenous carrier protein (hapten carrier principle) . Only the complex of protein and bound hapten is then the full-fledged antigen: A hapten becomes an antigen by “grabbing” a carrier protein.

One theory is that the hapten changes the tertiary structure of the protein so that its immune-relevant epitopes are reconfigured, and that the body no longer perceives the modified protein as endogenous but as foreign - an immune reaction is initiated.

Haptens played an important role in studying the body's immune responses. With their help, the immunologist Karl Landsteiner was able to prove that antibodies can be highly selective.

The dangerousness of haptens stems from the fact that by binding to specific cell structures they can trigger an immune reaction that leads to the destruction of a certain cell population. Normally the immune system recognizes the body's own structures, but these are changed by the haptens in such a way that they have an alien effect - in this way an autoimmune disease can be set in motion.

swell

• Werner Müller Esterl: Biochemistry. Spectrum Academic Publishing House, Munich / Heidelberg 2004, ISBN 978-3-8274-0534-0 .