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Questions and Answers
What are natural antibodies?
Which type of antibodies react against heterophile antigens?
What is the primary function of complement-fixing antibodies?
Which type of antibodies are produced in response to an immunogen?
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What is the primary function of opsonins?
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Which class of immunoglobulin is considered the best opsonin?
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What is the primary function of neutralizing antibodies?
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Which type of antibodies are responsible for agglutination reactions?
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What is the primary function of precipitins?
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Which type of antibodies are responsible for allergic reactions?
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Which type of antibody is primarily responsible for neutralizing toxins and viruses?
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Which antibody class is considered the most powerful agglutinator of particulate antigens?
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Which antibody class is primarily responsible for opsonization and phagocytosis?
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Which of the following antibody classes is primarily involved in immediate hypersensitivity reactions?
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Which antibody class is considered the first line of defense in mucosal immunity?
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Which antibody class is primarily responsible for complement fixation during the primary immune response?
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Which antibody class is capable of crossing the placenta and providing passive immunity to the newborn?
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Which antibody class is primarily involved in the selection and activation of naive B cells?
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Which antibody class is considered the most effective in complement fixation?
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Which antibody class is primarily associated with immunity against polysaccharide antigens?
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Study Notes
Antibody Structure and Function
- Antibodies are specific glycoproteins referred to as immunoglobulins, found in blood plasma and many body fluids.
- Primary function is to combine with antigens, leading to bacterial or viral neutralization.
- Main humoral element of the adaptive immune response.
Immunoglobulin (Ig) Classes
- Divided into 5 major classes based on heavy chain: IgG, IgM, IgA, IgD, and IgE.
Antibody Binding Sites
- Each antibody has at least 2 identical sites that bind antigen (valence).
- Most antibodies are bivalent.
Properties of Antibodies
- Protein in nature with high molecular weight.
- Present in serum/plasma, saliva, semen, CSF, and other body fluids.
General Functions of Immunoglobulins
- Neutralize toxic substances.
- Facilitate phagocytosis and kill microbes.
- Combine with antigens on cellular surfaces, causing destruction of cells.
Classification of Antibodies
- According to sedimentation constant: IgG, IgA, IgM, IgD, and IgE.
- According to temperature: cold antibodies (IgM) and warm antibodies (IgG).
- According to occurrence: natural antibodies and immune antibodies.
- According to reaction with antigen: agglutinins, hemagglutinins, precipitins, and lysins.
Structure of Immunoglobulin
- Basic structural unit of an antibody: monomer.
- Consists of 2 heavy chains and 2 light chains.
- Heavy chain: gamma, alpha, mu, delta, and epsilon.
- Light chain: kappa and lambda.
3-Dimensional Structure of Antibodies
- Folded into compact globular subunits based on the formation of balloon-shaped loops at each domain.
Enzyme Digestion
- Papain digestion: breaks the immunoglobulin molecule in the hinge region, producing Fab and Fc fragments.
- Pepsin digestion: cleaves the heavy chain after the H-H interchain disulfide bonds, resulting in an F(ab')2 fragment.
Immunoglobulin G (IgG)
- Most predominant immunoglobulin.
- Only antibody that can pass through the placenta, providing immunity to the newborn.
- Equally distributed in different fluid compartments.
- Mediates complement fixation and opsonization.
Immunoglobulin A (IgA)
- Found in serum in small amounts but predominant in sero-mucous secretions.
- Provides immunity to the infant digestive tract.
- Acts as a first line of defense for natural immunity.
Immunoglobulin M (IgM)
- Powerful agglutinator of particulate antigen.
- Does not cross the placenta.
- First antibodies produced during an infection.
- Has 10 binding sites (pentamer).
Immunoglobulin D (IgD)
- Heat-labile immunoglobulin.
- Detected by highly sensitive assays requiring radio-labeled antisera.
- Precise biological action is not known, but may play a role in antigen-triggered lymphocyte differentiation.
Immunoglobulin E (IgE)
- Most heat-labile immunoglobulin.
- Bound to mast cells and basophils throughout the body.
- Synthesized locally by plasma cells present in the mucous membrane of the GI and respiratory tracts.
- Associated with immediate hypersensitivity reactions and immunity to certain helminthic parasites.
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Description
This quiz covers the topic outline of Antibody Structure and Function, including the Classification of Antibodies, Structure of Immunoglobulin, 3-Dimensional Structure of Antibodies, Enzyme Digestion, Immunoglobulin Classes, and Theories of Antibody Production. Explore the concepts related to antibody structure, function, and binding to various cell types.
