Definition of antigen

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Definition of Antigen

Introduction to Antigens

An antigen is a substance that can trigger an immune response in the body. This response is typically characterized by the production of specific antibodies or the activation of immune cells that target the antigen 124. Antigens are crucial in the body's defense mechanism against pathogens such as bacteria, viruses, fungi, and parasites .

Types of Antigens

Complete Antigens

Complete antigens, also known as immunogens, are substances that can both induce an immune response and react with the products of that response, such as antibodies or T-cell receptors 46. These antigens are typically large molecules, such as proteins or polysaccharides, that are recognized as foreign by the immune system 57.

Incomplete Antigens (Haptens)

Incomplete antigens, or haptens, are small molecules that cannot induce an immune response on their own. However, when they are attached to a larger carrier molecule, they can become immunogenic and elicit an immune response 468. Examples of haptens include small peptides, pesticides, antibiotics, and hormones .

Molecular Nature of Antigens

Antigens can be composed of various types of molecules, including proteins, polysaccharides, lipids, and nucleic acids 57. The specific part of the antigen that is recognized by the immune system is called an epitope. Epitopes can be linear, consisting of a sequence of amino acids, or conformational, formed by the three-dimensional structure of the antigen .

Role in Immune Response

When an antigen enters the body, it is recognized as foreign by the immune system, which then mounts a response to eliminate it. This response can involve the production of antibodies by B cells, the activation of T cells, or both 46. The immune system's ability to distinguish between self and non-self is crucial in preventing autoimmune reactions, where the body attacks its own tissues .

Applications in Medicine

Antigens play a vital role in the development of vaccines and diagnostic tests. Vaccines often contain antigens that stimulate the immune system to produce a protective response without causing disease . In diagnostic tests, such as immunoassays, antigens are used to detect the presence of specific antibodies in a sample, indicating exposure to a particular pathogen .

Conclusion

In summary, antigens are substances that can trigger an immune response, leading to the production of antibodies or the activation of immune cells. They can be complete antigens, capable of inducing an immune response on their own, or incomplete antigens, which require a carrier molecule to become immunogenic. Understanding the nature and function of antigens is essential in immunology, vaccine development, and diagnostic testing.

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Most relevant research papers on this topic

Antigenic: An improved prediction model of protective antigens

Our novel computational model, Antigenic, effectively predicts protective antigens from protein sequences, improving vaccine preparation and drug design.

2019·

26citations

·M. Rahman et al.

Chapter 3 – Antigens

Antigens are substances perceived as foreign to the body, provoking specific immune responses, with antibody production directed against specific structures on their surface.

1985·

0citations

·S. Hammarström et al.

An Analysis of Bacterial Antigens on the Basis of Chemistry and Function

Bacterial antigens are proteins that cause changes in the animal body, such as precipitation, agglutination, or lysis, depending on their nature and the circumstances in which they are introduced into the body.

1931·

0citations

·Alston Jm

Antigens, Immunogens, Vaccines, and Immunization

Immunogens and antigens play a crucial role in inducing immune responses against infectious agents, and vaccines are effective tools for preventing disease.

1999·

3citations

·J. Cruse et al.

The nature of the antigen.

Antigens are any substance that provokes the production of specific antibodies or immunocytes, and can be proteins, polysaccharides, or nucleic acids, with superantigens being a subgroup of microbial antigens.

1996·

16citations

·M. Sela et al.

Basic principles of Antigen-Antibody Reactions.

Antigen-antibody reactions involve the formation of antibodies against specific substances, with various antigenic determinants on macromolecules and complex glycoproteins playing a role in these interactions.

1980·

53citations

·E. Kabat

Antigens and Immunogens

Antigens and immunogens are both substances capable of stimulating specific immune responses, but their definitions depend on the host's response to them rather than intrinsic molecular properties of the substance itself.

1981·

1citation

·F. Mcduffie

Antigen and antibody.jpg

Immunoassays identify and quantify unknown analytes using specific antibody-antigen reactions, enabling the identification of immune system responses.

2016·

0citations

·Yudong Lu

REVIEW OF ANTIGEN AND ANTIBODY INTERACTION

Antigen-antibody interaction plays a crucial role in protecting the body from complex foreign molecules, such as pathogens and their chemical toxins, by specifically binding and transporting them to cellular systems for destruction or deactivation.

2019·

0citations

·Gurpreet Singh

Antigen processing and presentation.

Dendritic cells play a crucial role in presenting complex antigens to T cells, triggering immune responses against pathogens.

2019·

67citations

·Fiorella Kotsias et al.

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