What are Antibodies and How Do They Work?
Antibodies, also known as immunoglobulins, are Y-shaped proteins produced mainly by plasma cells that are part of the body's immune system. Antibodies recognize and help eliminate pathogens such as bacteria and viruses. Each antibody recognizes a specific antigen unique to its target. Our bodies produce millions of antibodies, each with a unique shape that allows it to bind to its matching antigen.
Antibody Structure
Antibodies are made up of basic structural units called immunoglobulin. Each immunoglobulin contains a variable region that recognizes antigens and a constant region that interacts with other parts of the immune system. The variable region contains antigen-binding sites that give antibodies their specificity. There are two light chains and two heavy chains linked together to form a symmetric Y shape. The fragment antigen-binding (Fab) region at the two tips of antibody binds to the antigen, while the fragment crystallizable (Fc) region interacts with effector cells of the immune system.
How Antibodies Recognize Antigens
The antigen-binding region of an antibody contains a patchwork of amino acids that give it flexibility to recognize the unique shape and chemical features of its target antigen. When an antibody encounters its matching antigen, this region strongly binds to complementary sites on the antigen surface in a "lock and key" mechanism. Only antibodies with amino acids arranged in the proper order and conformation can precisely fit and bind the antigen. Factors like hydrogen bonds, salt bridges and hydrophobic interactions all contribute to this tight binding between antigen and antibody.
Classes and Subclasses of Antibodies
There are five major classes of antibodies in mammals: IgA, IgD, IgE, IgG, and IgM. They differ in structure and function depending on the region of the body where they act. IgG is the most abundant type in blood and tissues, comprising about 75% of serum antibodies. It plays a major role in complement activation and defense against bacteria and viruses. IgA is predominantly found in external secretions such as tears, saliva and intestine where it helps prevent colonization by pathogens. IgM is the first antibody produced during infection and has a pentameric structure that allows it to activate complement rapidly. IgE is involved in allergic reactions and defense against parasites, while IgD functions are still not fully understood.
How Antibodies Mediate Defense
Antibodies use several methods to recognize, neutralize and help eliminate pathogens from the body:
- Agglutination - Cross-linking of antibodies on a pathogen surface can cause clumping or agglutination thatrestricts mobility. This process promotes phagocytosis.
- Neutralization - Antibodies may block cellular receptors on viruses or neutralize soluble toxins by binding and preventing them from binding target cells.
- Opsonization - Antibodies bound to pathogens promote their recognition and ingestion by phagocytes through Fc receptors.
- Activation of Complement System - Antibody Fc regions trigger complement activation cascades that directly lyse or induce chemotaxis for pathogens.
- Activation of NK Cells - Antibody-coated pathogens activate Natural Killer cells that can directly kill infected cells.
Together these immune mechanisms allow antibodies to orchestrate both innate and adaptive immune defenses against a wide range of microbes. Antibody levels are also monitored clinically through serology to diagnose acute and past infectious diseases. Overall, the incredible diversity and mechanisms of antibodies make them crucial sentinels of our immune health and protection from pathogens.
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About Author:
Alice Mutum is a seasoned senior content editor at Coherent Market Insights, leveraging extensive expertise gained from her previous role as a content writer. With seven years in content development, Alice masterfully employs SEO best practices and cutting-edge digital marketing strategies to craft high-ranking, impactful content. As an editor, she meticulously ensures flawless grammar and punctuation, precise data accuracy, and perfect alignment with audience needs in every research report. Alice's dedication to excellence and her strategic approach to content make her an invaluable asset in the world of market insights.
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