Questions and Answers
What is an immunoglobulin?
An antibody produced by plasma cells that identifies and neutralizes pathogens.
Describe the structure of an immunoglobulin.
Two heavy chains and two light chains with variable and constant regions.
Which of the following are isotypes of immunoglobulins?
What are idiotypes?
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Which immunoglobulins can be transferred through the placenta?
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What is the primary antibody produced during the initial immune response?
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What type of immunoglobulin is involved in opsonization?
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Which immunoglobulin is involved in triggering allergic reactions?
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IgA can be either ___ or ___ connected by a J-chain.
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Match the following immunoglobulins with their characteristics:
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What immunoglobulins are involved in neutralization?
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Which immunoglobulin is primarily present on the surface of naïve B-cells?
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Study Notes
Immunoglobulins Overview
- Immunoglobulins, or antibodies (Ab), are Y-shaped proteins produced by B-lymphocytes, crucial for the immune response against pathogens like bacteria and viruses.
Structure of Immunoglobulins
- Composed of two heavy chains (450 amino acids each) containing one variable and three constant domains, and two light chains (212 amino acids each) with one variable and one constant domain.
- The variable region binds to antigens with high specificity, while the constant region determines the antibody's functional response to the bound antigen.
- The hinge region allows antibodies flexibility for binding multiple antigens.
Isotypes of Immunoglobulins
- Five major classes: IgM, IgG, IgD, IgA, IgE.
- Differences among isotypes are found in the constant part of the immunoglobulin, which provides distinct antigenic determinants.
Idiotypes
- Idiotypes refer to shared characteristics among groups of immunoglobulins or T cell receptors based on their variable region's structure and antigen-binding specificity.
- Unique sequences in the variable region determine the antigen specificity.
Types of Immunoglobulins
- IgG: Major immunoglobulin produced after IgM; involved in opsonization, complement activation, neutralization, and can cross the placenta.
- IgM: First antibody produced; pentameric structure with five potential binding sites; activates complement and present on naive B-cells; cannot cross placenta.
- IgA: Exists as monomeric or dimeric (linked by J-chain); found in secretions; inhibits mucosal binding without activating the complement.
- IgD: Primarily located on naive B-cells; role in immune response initiation.
- IgE: Protects against parasites; binds to mast cells and basophils; associated with type I hypersensitivity reactions.
Forms of Immunoglobulins
- Immunoglobulins exist in various forms:
- Monomers: IgD, IgE, IgG
- Dimers: IgA
- Pentamers: IgM
Functions and Mechanisms
- Activation of Complement: Primarily through IgG and IgM.
- Opsonization: Mediated by IgG, enhancing phagocytosis.
- Neutralization: Achieved by IgG, IgA, and IgM, preventing pathogen activation.
- Adherence Interfering: Involves IgA and IgG, preventing binding to surfaces.
- Antibody-Dependent Cell-Mediated Cytotoxicity: Carried out by IgG, recruiting immune cells to destroy infected cells.
- Agglutination: Occurs with IgG and IgM, clumping pathogens together for elimination.
- Mast Cell Degranulation: Triggered by IgE, leading to histamine release during allergic reactions.
Unique Characteristics
- IgG is the only immunoglobulin that can cross the placenta, providing passive immunity to the fetus.
- IgG also plays a significant role in immunoregulation within the immune system.
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Description
This quiz covers the essential aspects of immunoglobulins, including their structure, types, and functions in the immune response. Understand the Y-shaped proteins produced by B-lymphocytes and their significance in combating pathogens. Test your knowledge on the isotypes and idiotypes of antibodies.
