Describe the structure of antibody

Guide to the structural components that make up an antibody - heavy chains, light chains, F(ab)/Fc regions - and antibody isotypes. Updated May 9, 2022. Antibody structure Antibodies, also known as immunoglobulins (Ig), are large, Y-shaped glycoproteins produced by B-cells as a primary immune defense. Antibodies specifically bind unique pathogen moleculescalled Antibodies exist as one or more copies of a Y-shaped unit composed of four polypeptide chains (Fig. 1). Each Y unit contains two identical copies of a heavy chain (H) and two identical copies of a light chain (L); heavy and light chains differ in their sequence and length. The top of the Y shape contains the variable region (V), also known as the fragment antigen-binding (F(ab)) region. This region binds tightly to a specific part of an antigen called an epitope. The antibody base consists of constant domains (C) and forms the fragment crystallizable region (Fc). This region is essential for the function of the antibody during an immune response. Antibodies exist as one or more copies of a Y-shaped unit composed of four polypeptide chains (Fig. 1). Each Y unit contains two identical copies of a heavy chain (H) and two identical copies of a light chain (L); heavy and light chains differ in their sequence and length. The top of the Y shape contains the variable region (V), also known as the fragment antigen-binding (F(ab)) region. This region binds tightly to a specific part of an antigen called an epitope. Figure 1.A...

\( \newcommand\) • • • • • • A region at the tip of the antibody protein is very variable, allowing millions of antibodies with different antigen-binding sites to exist. Key Points • An antibody (Ab), also known as an immunoglobulin (Ig), is a large protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen. • Each tip of the “Y” of an antibody contains a paratope that is specific for one particular epitope (analogous to a lock and key) on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell. • The general structure of all antibodies is very similar: The Ig monomer is a Y-shaped molecule that consists of four polypeptide chains: two identical heavy chains and two identical light chains connected by disulphide bonds. • Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B-cell and is referred to as the B-cell receptor (BCR). Key Terms • Hypervariable region: In antibodies, hypervariable regions form the antigen-binding site and are found on both light and heavy chains. They also contribute to the specificity of each antibody. In a variable region, the 3 HV segments of each heavy or light chain fold together at the N-term...

Immunoglobulin A (IgA) Immunoglobulin A (IgA) is primarily found in mucosal tissues, such as those in the mouth, vagina, and intestines, as well as in saliva, tears, and breast milk. It accounts for 15% of all antibodies in the human body and is produced by B cells and secreted from the lamina propria, a thin layer within mucosal tissues. Immunoglobulin M (IgM) Immunoglobulin M (IgM) is also one of the first antibodies recruited by the immune system to fight infection. IgM populations rise very quickly when the body is first confronted with an infectious organism, and then they plummet as IgG antibodies take over. IgM is also produced by B cells and, when bound to a pathogen, will spur other antibodies and immune cells into action. IgE also helps to protect the body from parasitic infections, including helminths (parasitic worms). Immunoglobulin D (IgD) Immunoglobulin D (IgD) is important in the early stages of the immune response. Unlike other antibodies, it does not actively circulate but instead binds to B cells to instigate the immune response. As a signaling antibody, IgD helps incite the release of front-line IgM to fight disease and infection. Antibody tests do not detect the actual pathogens that cause an infection—they detect the antibodies that are produced in response to the infection. A positive result means "yes," the test has detected the antibody or antigen. A negative result means "no," while borderline results are considered inconclusive. An antibody test ...

By Grace Plahe, BSc Reviewed by Vertebrates with a defined immune system, such as humans, have an immune response consisting of an innate and adaptive response, also known as a specific response. The specific response is tailored to the pathogen infecting the body and targets it specifically. The innate, or nonspecific, response combats any pathogen it encounters. Antibodies, also known as Immunoglobulins, are incredibly specific molecules that bind to their target antigen and neutralize it in the most common cases. They achieve this by promoting a change in structure, blocking binding sites needed to complete a function, or marking out the cell they are bound to for phagocytosis. They can also aid the precipitation of When detected, the body generally produces them in response to toxins or other pathogenic items. They are part of the specific immune response and are generated to combat known threats. Antibodies can also play a therapeutic role and are used to influence specific metabolic pathways. Image Credit:periyanayagam/Shutterstock.com Immunoglobulin (Ig) molecules are "Y" shaped glycoproteins that consist of two heavy and two light chains. The light chains are made up of two domains, and the heavy ones are made up of four. These domains all have constant and variable regions accounting for the wide variations in structure seen between molecules. The arms of the "Y" form are made up of light chains, and the N-terminal of the heavy chains tightly bound together. The b...

1 An Introduction to the Human Body • Introduction • 1.1 Overview of Anatomy and Physiology • 1.2 Structural Organization of the Human Body • 1.3 Functions of Human Life • 1.4 Requirements for Human Life • 1.5 Homeostasis • 1.6 Anatomical Terminology • 1.7 Medical Imaging • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 2 The Chemical Level of Organization • Introduction • 2.1 Elements and Atoms: The Building Blocks of Matter • 2.2 Chemical Bonds • 2.3 Chemical Reactions • 2.4 Inorganic Compounds Essential to Human Functioning • 2.5 Organic Compounds Essential to Human Functioning • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 3 The Cellular Level of Organization • Introduction • 3.1 The Cell Membrane • 3.2 The Cytoplasm and Cellular Organelles • 3.3 The Nucleus and DNA Replication • 3.4 Protein Synthesis • 3.5 Cell Growth and Division • 3.6 Cellular Differentiation • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 4 The Tissue Level of Organization • Introduction • 4.1 Types of Tissues • 4.2 Epithelial Tissue • 4.3 Connective Tissue Supports and Protects • 4.4 Muscle Tissue and Motion • 4.5 Nervous Tissue Mediates Perception and Response • 4.6 Tissue Injury and Aging • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 5 The Integumentary ...

\( \newcommand\) • • Learning Objectives • Describe an antibody molecule. • Draw the "stick figure" structure of IgG, indicating the Fab portion (variable region) and the Fc portion (constant region). • State the functions of the Fab and the Fc portions of an antibody. • State what is meant by the biological activity of an antibody. • Compare the structure of IgM and secretory IgA with that of IgG. In this section we will look at the structure of antibodies. There are five classes or isotypes of human antibodies : • immunoglobulin G (IgG), • immunoglobulin M (IgM), • immunoglobulin A (IgA), • immunoglobulin D (IgD), and • immunoglobulin E (IgE). The simplest antibodies, such as IgG, IgD, and IgE, are "Y"-shaped macromolecules called monomers. A monomer is composed of four glycoprotein chains: two identical heavy chains and two identical light chains. The two heavy chains have a high molecular weight that varies with the class of antibody. The light chains come in two varieties: kappa or lambda and have a lower molecular weight than the heavy chains. The four glycoprotein chains are connected to one another by disulfide (S-S) bonds and non-covalent bonds (Figure \(\PageIndex\)) is a dimer consisting of 2 "Y"-like molecules connected at their Fc portions by a "J" chain and stabilized to resist enzymatic digestion in body secretions by means of a secretory component. Summary • There are 5 classes or isotypes of human antibodies or immunoglobulins: IgG, IgM, IgA, IgD, and IgE....

By Grace Plahe, BSc Reviewed by Vertebrates with a defined immune system, such as humans, have an immune response consisting of an innate and adaptive response, also known as a specific response. The specific response is tailored to the pathogen infecting the body and targets it specifically. The innate, or nonspecific, response combats any pathogen it encounters. Antibodies, also known as Immunoglobulins, are incredibly specific molecules that bind to their target antigen and neutralize it in the most common cases. They achieve this by promoting a change in structure, blocking binding sites needed to complete a function, or marking out the cell they are bound to for phagocytosis. They can also aid the precipitation of When detected, the body generally produces them in response to toxins or other pathogenic items. They are part of the specific immune response and are generated to combat known threats. Antibodies can also play a therapeutic role and are used to influence specific metabolic pathways. Image Credit:periyanayagam/Shutterstock.com Immunoglobulin (Ig) molecules are "Y" shaped glycoproteins that consist of two heavy and two light chains. The light chains are made up of two domains, and the heavy ones are made up of four. These domains all have constant and variable regions accounting for the wide variations in structure seen between molecules. The arms of the "Y" form are made up of light chains, and the N-terminal of the heavy chains tightly bound together. The b...

Term Meaning Pathogen A disease-causing organism, including bacteria, Antigen Molecule that stimulates an immune response Innate immune system Non-specific immune system Adaptive immune system Antigen-specific immune system Antibody Specialized Y-shaped protein that tags antigens for destruction B cells White blood cells that produce antibodies and aid in immunological memory T cells White blood cells specialized to assist B cells (helper T) and others directly kills infected cells (killer T) Humoral immunity Adaptive immune defense depending on the action of antibodies Cell-mediated Immunity Adaptive immune defense in which foreign cells are destroyed by T cells Virus Nonliving particle containing protein and DNA/RNA that can infect a living cell Vaccine A killed or weakened form of a pathogen that produces immunity when injected into the body An inflammatory response begins when a pathogen stimulates an increase in blood flow to the infected area. Blood vessels in that area expand, and white blood cells leak from the vessels to invade the infected tissue. These white blood cells, called phagocytes engulf and destroy bacteria. The area often becomes red, swollen, and painful during an inflammatory response. Specific immune responses are triggered by antigens. Antigens are usually found on the surface of pathogens and are unique to that particular pathogen. The immune system responds to antigens by producing cells that directly attack the pathogen, or by producing special ...

1 An Introduction to the Human Body • Introduction • 1.1 Overview of Anatomy and Physiology • 1.2 Structural Organization of the Human Body • 1.3 Functions of Human Life • 1.4 Requirements for Human Life • 1.5 Homeostasis • 1.6 Anatomical Terminology • 1.7 Medical Imaging • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 2 The Chemical Level of Organization • Introduction • 2.1 Elements and Atoms: The Building Blocks of Matter • 2.2 Chemical Bonds • 2.3 Chemical Reactions • 2.4 Inorganic Compounds Essential to Human Functioning • 2.5 Organic Compounds Essential to Human Functioning • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 3 The Cellular Level of Organization • Introduction • 3.1 The Cell Membrane • 3.2 The Cytoplasm and Cellular Organelles • 3.3 The Nucleus and DNA Replication • 3.4 Protein Synthesis • 3.5 Cell Growth and Division • 3.6 Cellular Differentiation • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 4 The Tissue Level of Organization • Introduction • 4.1 Types of Tissues • 4.2 Epithelial Tissue • 4.3 Connective Tissue Supports and Protects • 4.4 Muscle Tissue and Motion • 4.5 Nervous Tissue Mediates Perception and Response • 4.6 Tissue Injury and Aging • Key Terms • Chapter Review • Interactive Link Questions • Review Questions • Critical Thinking Questions • 5 The Integumentary ...

\( \newcommand\) • • • • • • A region at the tip of the antibody protein is very variable, allowing millions of antibodies with different antigen-binding sites to exist. Key Points • An antibody (Ab), also known as an immunoglobulin (Ig), is a large protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen. • Each tip of the “Y” of an antibody contains a paratope that is specific for one particular epitope (analogous to a lock and key) on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell. • The general structure of all antibodies is very similar: The Ig monomer is a Y-shaped molecule that consists of four polypeptide chains: two identical heavy chains and two identical light chains connected by disulphide bonds. • Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B-cell and is referred to as the B-cell receptor (BCR). Key Terms • Hypervariable region: In antibodies, hypervariable regions form the antigen-binding site and are found on both light and heavy chains. They also contribute to the specificity of each antibody. In a variable region, the 3 HV segments of each heavy or light chain fold together at the N-term...