I. Introduction

Antigens are molecules that are capable of inducing a specific immune response. They are typically proteins or polysaccharides, but can also include lipids and nucleic acids. Antigen is recognized by the immune system as foreign and trigger the production of antibodies or the activation of T cells.

II. Types of Antigen

• There are two main types of antigens: endogenous and exogenous.
• Endogenous antigens are molecules that are naturally present in the body, such as self-antigens.
• Exogenous antigens are foreign molecules that enter the body, such as bacteria, viruses, and toxins.

III. Structure and Characteristics of Antigen

• Antigens can be divided into two main categories based on their structure: haptens and complete antigens.
• Haptens are small molecules that are unable to elicit an immune response on their own, but can do so when bound to a larger carrier molecule.
• Complete antigens, also known as immunogens, are able to elicit an immune response on their own.
• Antigens can also be characterized by their molecular weight, chemical properties, and stability.

IV. Antigen Processing and Presentation

Antigens must be processed and presented to the immune system in order to elicit a response.

Antigens that enter the body are first taken up by antigen-presenting cells (APCs), such as dendritic cells and macrophages.

These cells then process the antigens and present them on their surface, along with major histocompatibility complex (MHC) molecules, to T cells.

V. Immune Recognition

Antigens are recognized by the immune system through the binding of antibodies or T cell receptors (TCRs) to the antigen-MHC complex.

Antibodies are produced by B cells and are specific to a particular antigen.

TCRs are expressed on the surface of T cells and can bind to a wide range of antigens.

VI. Conclusion

Antigens are molecules that are capable of inducing a specific immune response.

They are typically proteins or polysaccharides, but can also include lipids and nucleic acids.

Antigens are recognized by the immune system as foreign and trigger the production of antibodies or the activation of T cells.

Antigens must be processed and presented to the immune system in order to elicit a response.

Antigens are recognized by the immune system through the binding of antibodies or T cell receptors (TCRs) to the antigen-MHC complex.