- Structure Of Antigens: Acquired immunity, a remarkable defense mechanism, is only triggered when the body encounters foreign organisms or toxins.
- In general, these are proteins or large polysaccharides and these compounds initiate acquired immunity. These are called antigens. The response of the body to the presence of any foreign agent (antigen) is called immune response. Antigens, the architects of our immune response, are defined as substances that provoke an immune reaction within the body. They come in various forms, including proteins, carbohydrates, and lipids.
- Notably, these compounds tend to have a substantial molecular weight, typically exceeding 8000.
- Also, antigenicity depends on the presence of regularly recurring molecular groups called epitopes or antigenic determinants on the surface of the large molecule.
- Epitopes serve as the building blocks of antigens, acting as the smallest unit to which antibodies or immune cells can bind.
- In the case of proteins, antibodies attach to epitopes that are approximately three to six amino acids in length, while carbohydrates exhibit epitopes comprising about five to six sugar residues.
- Consequently, a single large antigen can feature multiple antigenic determinants, which may either be identical or distinct from one another within the same molecule.
Variability in Antigenic Responses
- Acknowledging that not all antigenic determinants within an antigen wield equal influence is essential.
- Some may elicit strong and others weak responses. This variability is influenced by factors such as an individual’s health, age, and genetic makeup.
- Consequently, the same antigen may provoke diverse responses in different people based on their unique physiological characteristics.
- While antigens predominantly comprise large molecules, there exists a peculiar category of low molecular weight compounds known as haptens. T
- hese substances, which include certain drugs, components found in dust, and industrial chemicals, possess the potential to incite an immune response. However, haptens cannot achieve this feat on their own. Instead, they must form a complex with another antigenic compound to trigger a reaction.
- This collaboration between haptens and other antigens showcases the intricacies of our immune system’s responses to a wide range of foreign substances.
- When a specific antigen encounters T and B-cells within the lymphoid tissues, a remarkable transformation takes place.
- Certain T-cells become activated, evolving into activated T-cells, while specific B-cells are stimulated to produce antibodies.
- These activated cells then embark on a journey of replication, generating numerous copies of themselves. This process results in the formation of a unique group of lymphocytes: the clone of B lymphocytes and a particular type of T-cells with a single specificity.
- The clone of B cells secrete a specific type of antibody, which circulate through the body, while the clone of T-cells are released into the lymph, carried to the blood and circulated through all the tissue fluid and back into the lymph. They can circulate around and around in this circuit for months or years.
Antibody: Structure, classes and functions