World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0000555023
Reproduction Date:

Title: Hapten  
Author: World Heritage Encyclopedia
Language: English
Subject: Immune system, Urushiol, Antigenicity, Pentafluorophenyl esters, Lymphocytic immune system
Collection: Immune System
Publisher: World Heritage Encyclopedia


Haptens are small molecules that elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself. (In general, only large molecules, infectious agents, or insoluble foreign matter can elicit an immune response in the body.) Once the body has generated antibodies to a hapten-carrier adduct, the small-molecule hapten may also be able to bind to the antibody, but it will usually not initiate an immune response; usually only the hapten-carrier adduct can do this. Sometimes the small-molecule hapten can even block immune response to the hapten-carrier adduct by preventing the adduct from binding to the antibody, a process called hapten inhibition.

The mechanisms of absence of immune response may vary and involve complex immunological mechanisms, but can include absent or insufficient co-stimulatory signals from antigen-presenting cells.

The concept of haptens emerged from the work of Karl Landsteiner[1] [2] who also pioneered the use of synthetic haptens to study immunochemical phenomena.[3]


  • Examples of haptens 1
  • Hapten inhibition 2
  • See also 3
  • References 4
  • External links 5

Examples of haptens

The first researched haptens were aniline and its carboxyl derivatives (o-, m-, and p-aminobenzoic acid).[4]

A well-known example of a hapten is urushiol, which is the toxin found in poison ivy. When absorbed through the skin from a poison ivy plant, urushiol undergoes oxidation in the skin cells to generate the actual hapten, a reactive molecule called a quinone, which then reacts with skin proteins to form hapten adducts. Usually, the first exposure causes only sensitization, in which there is a proliferation of effector T-cells. After a subsequent, second exposure, the proliferated T-cells can become activated, generating an immune reaction that produces typical blisters of a poison ivy exposure.

Some haptens can induce autoimmune disease. An example is hydralazine, a blood pressure-lowering drug that occasionally can produce drug-induced lupus erythematosus in certain individuals. This also appears to be the mechanism by which the anaesthetic gas halothane can cause a life-threatening hepatitis, as well as the mechanism by which penicillin-class drugs cause autoimmune hemolytic anemia.

Other haptens that are commonly used in molecular biology applications include fluorescein, biotin, digoxigenin, and dinitrophenol.

Hapten inhibition

Hapten inhibition or "semi-hapten" is the inhibition of a type III hypersensitivity response. In inhibition, free hapten molecules bind with antibodies toward that molecule without causing the immune response, leaving fewer antibodies left to bind to the immunogenic hapten-protein adduct. An example of a hapten inhibitor is dextran 1, which is a small fraction (1 kilodalton) of the entire dextran complex, which is enough to bind anti-dextran antibodies, but insufficient to result in the formation of immune complexes and resultant immune responses.[5]

See also


  1. ^ Landsteiner, Karl (1945). The Specificity of Serological Reactions. Cambridge: Harvard Univ. Press. 
  2. ^ Landsteiner, Karl (1990). The Specificity of Serological Reactions, 2nd Edition, revised. Courier Dover Publications.  
  3. ^ Shreder, Kevin (March 2000). "Synthetic Haptens as Probes of Antibody Response and Immunorecognition". Methods (Academic Press) 20 (3): 372–379.  
  4. ^ Based on K. Landsteiner, 1962, The Specificity of Serologic Reactions, Dover Press
  5. ^ Promiten, drug information from the Swedish official drug catalog Last updated: 2005-02-17

External links

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.