What is an antibody?
The correct answer and explanation is :
An antibody, also known as an immunoglobulin, is a protein produced by the immune system to help defend the body against foreign invaders, such as bacteria, viruses, fungi, or toxins. Antibodies are produced primarily by B cells, a type of white blood cell, in response to the presence of antigens—specific molecules found on the surface of pathogens or other harmful substances.
Each antibody is highly specific, meaning it is designed to recognize and bind to a particular antigen. The structure of an antibody consists of two main regions: the variable region and the constant region. The variable region is responsible for recognizing and binding to the antigen, while the constant region is involved in triggering immune responses, such as activating other immune cells or proteins to eliminate the threat.
Antibodies work by neutralizing the threat in several ways:
- Neutralization: Antibodies can directly block the pathogen’s ability to infect cells by binding to the pathogen’s surface or the toxins it produces.
- Opsonization: They coat the pathogen, marking it for destruction by other immune cells like macrophages and neutrophils.
- Complement Activation: The binding of antibodies to an antigen can activate the complement system, a group of proteins that assists in destroying pathogens.
There are five main classes of antibodies: IgG, IgA, IgM, IgE, and IgD. Each class plays a different role in immune defense, with IgG being the most abundant and effective in neutralizing infections, and IgE being involved in allergic reactions.
Antibodies are also the basis for various medical applications, such as diagnostic tests, vaccines, and antibody therapies, where they are used to treat diseases or enhance the immune response against specific pathogens.
In summary, antibodies are crucial components of the immune system, playing a vital role in identifying and neutralizing foreign invaders to protect the body from infections and diseases.