The key difference between hapten and adjuvant is that hapten is a small molecule that elicits an immune response only when attached to a larger carrier such as an antibody, while adjuvant is a pharmacological or immunological agent that modifies the effect of other agents.
Hapten and adjuvant are two molecules that are extremely important for the immune system. Hapten can be described as an incomplete antigen. It binds with larger proteins such as antibodies. Adjuvant, on the other hand, binds to proteins such as antigens. Therefore, adjuvants are very important in vaccination therapy.
CONTENTS
1. Overview and Key Difference
2. What is a Hapten
3. What is an Adjuvant
4. Similarities – Hapten and Adjuvant
5. Hapten vs Adjuvant in Tabular Form
6. Summary – Hapten vs Adjuvant
What is a Hapten?
A hapten is a small molecule that elicits an immune response only when attached to a larger carrier, such as an antibody. A hapten is a lower molecular weight agent that reacts with specific antibodies, but it is not immunogenic by itself. It can only be made immunogenic by conjugation to a suitable carrier (antibody). Sometimes, the carrier or antibody also does not elicit an immune response itself due to various reasons, such as absent or insufficient co-stimulatory signals from antigen-presenting cells. The concept of hapten first came into use with Australian immunologist Karl Landsteiner. He used synthetic haptens to study the immunochemical phenomena.
Figure 01: Hapten
Haptens are usually used in the scientific field to study allergic contact dermatitis and the mechanism of inflammatory bowel disease (IBD) to induce autoimmune-like responses in the human gastrointestinal tract. Most drugs like penicillin are also haptens. The first researched haptens are aniline and its carboxyl derivatives. Furthermore, other commonly used haptens in molecular biology include fluorescein, biotin, digoxigenin, and dinitrophenol. However, some haptens can induce autoimmune diseases. An example of this is hydralazine, which is a blood pressure-lowering drug that can induce lupus erythematosus.
What is an Adjuvant?
An adjuvant is a pharmacological or immunological agent that modifies the effect of other agents. Immunizing antigens sometimes leads to a poor immune response. Sometimes, antigens are rapidly removed from the body. To prevent this, antigens are first combined with adjuvants. Adjuvant helps to stimulate and enhance the immune response against antigens. Adjuvants can function in various ways in presenting an antigen to the immune system. Therefore, adjuvants present antigens to the immune system over a long period of time, maximizing the immune response before the body clears antigens. Because of this, adjuvants are extremely important in vaccination therapy.
Figure 02: Adjuvant
The immunological functions of adjuvants include improving the immunogenicity of recombinant antigens, increasing the innate immune response to antigens by interacting with PRR receptors on accessory cells, providing protection to antigens physically, and helping in the translocation of antigens to the lymph nodes.
What are the Similarities Between Hapten and Adjuvant?
- Hapten and adjuvant are two molecules that are extremely important in immunogenicity and for the immune system.
- Both molecules have specific immunological functions.
- They are extremely important for human survival.
- Both molecules have side effects.
What is the Difference Between Hapten and Adjuvant?
A hapten is a small molecule that elicits an immune response only when attached to a larger carrier, such as an antibody. At the same time, an adjuvant is a pharmacological or immunological agent that modifies the effect of other agents. Thus, this is the key difference between hapten and adjuvant. Furthermore, hapten binds to proteins like antibodies, while adjuvant binds to proteins like antigens.
The below infographic presents the differences between hapten and adjuvant in tabular form for side-by-side comparison.
Summary – Hapten vs Adjuvant
Hapten and adjuvant are two molecules that are extremely important for the immune system. They have various immunological functions; thus, they help human survival. A hapten is a small molecule that elicits an immune response only when attached to a larger carrier such as an antibody. An adjuvant is a pharmacological or immunological agent that modifies the effect of other agents. So, this is the key difference between hapten and adjuvant.
Reference:
1.“Immunogen, Antigen, Hapten, Epitope, and Adjuvant.” Creative Diagnositcs.
2. “Adjuvants and Vaccines.” Centers for Disease Control and Prevention.
Image Courtesy:
1. “Hapten” By MantOs – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Fimmu-11-579250-g004” By Katie L. Flanagan, Emma Best, Nigel W. Crawford, Michelle Giles, Archana Koirala, Kristine Macartney, Fiona Russell, Benjamin W. Teh, and Sophie CH Wen, on behalf of the Australasian Society for Infectious Diseases (ASID) Vaccination Special Interest group (VACSIG) – Progress and Pitfalls in the Quest for Effective SARS-CoV-2 (COVID-19) Vaccines. Front. Immunol. 11:579250.https://doi.org/10.3389/fimmu.2020.579250 (CC BY 4.0) via Commons Wikimedia