Antibody Subtypes Quiz
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Questions and Answers

Which site on the immunoglobulin is responsible for binding with the complement?

  • CH2 (correct)
  • Fc Receptor
  • Heavy chain
  • CH3

    • What is the primary biological function mediated by the IgG subclass?

  • Phagocytosis
  • Cytokine production
  • Opsonization (correct)
  • Antigen presentation

    • Which Fc receptor type is characterized by high affinity binding to the Fc portion of Ig?

  • High affinity Fc receptor (correct)
  • Glycosylated Fc receptor
  • Low affinity Fc receptor
  • Multimeric Fc receptor

    • What is the half-life of IgG in circulation?

    <p>20 days</p> Signup and view all the answers

    How many sub-classes of IgG are there?

    <p>4</p> Signup and view all the answers

    Which part of the IgG is primarily responsible for interactions with Fcγ receptors?

    <p>Fcγ fragment</p> Signup and view all the answers

    Which of the following activities is NOT associated with immunoglobulins?

    <p>Producing antibodies</p> Signup and view all the answers

    What characteristic of the IgG subclasses allows for their flexibility?

    <p>Hinge region</p> Signup and view all the answers

    What determines the different isotypes of immunoglobulin (Ig) molecules?

    <p>Differences in the constant regions of both light and heavy chains</p> Signup and view all the answers

    When using a mouse polyclonal Ig as an immunogen in a rabbit, what type of antibodies are produced?

    <p>Rabbit anti-mouse isotypic antibodies</p> Signup and view all the answers

    Which type of immunoglobulin is present in external fluids like tears and saliva?

    <p>Secretory Ig</p> Signup and view all the answers

    What does the presence of a transmembrane domain indicate about an immunoglobulin?

    <p>It is a membrane Ig</p> Signup and view all the answers

    Which immunoglobulin allotype is produced when a mouse strain A Ig is injected into a mouse strain B?

    <p>Mouse B anti-mouse A</p> Signup and view all the answers

    What role does the lysosome play in the processing of an antigen by a B cell?

    <p>It degrades the antigen and BCR.</p> Signup and view all the answers

    What facilitates the joining of two monomers in secretory immunoglobulin to form a dimer?

    <p>A J chain</p> Signup and view all the answers

    How are MHC class II molecules relevant to T follicular cell activation?

    <p>They present processed antigens to T follicular cells.</p> Signup and view all the answers

    What happens to the B cell after it presents the antigen to a T follicular cell?

    <p>It receives signals to proliferate and differentiate.</p> Signup and view all the answers

    What is the main role of the intracytoplasmic domain in membrane immunoglobulin?

    <p>Anchoring the Ig to the B cell membrane</p> Signup and view all the answers

    What is the consequence of T follicular cells recognizing the antigen presented by B cells?

    <p>The T cells will release cytokines to assist B cell activation.</p> Signup and view all the answers

    Which of the following heavy chain isotypes is not found among the five mentioned?

    <p>β (beta)</p> Signup and view all the answers

    What is the final outcome for activated B cells?

    <p>They proliferate to form a clone and differentiate into plasma cells.</p> Signup and view all the answers

    What is the role of antibodies produced by plasma cells?

    <p>They neutralize pathogens and facilitate their elimination.</p> Signup and view all the answers

    Why is the interaction between the B cell and T follicular cell considered crucial?

    <p>It ensures a strong and lasting immune response.</p> Signup and view all the answers

    What specificity does the T cell receptor (TCR) possess in relation to the antigen presented by B cells?

    <p>It recognizes antigen in conjunction with MHC class II molecules.</p> Signup and view all the answers

    What is the primary function of maternal IgG in the context of infant health?

    <p>To protect the infant from infections for about 3 months after delivery</p> Signup and view all the answers

    What condition may arise in an infant due to a deficiency in IgG production after maternal IgG is depleted?

    <p>X-linked Bruton immunodeficiency</p> Signup and view all the answers

    How does maternal Graves' disease affect the newborn?

    <p>Newborn inherits antibodies against TSH receptors from the mother</p> Signup and view all the answers

    What major risk does an Rh– mother face when delivering an Rh+ baby?

    <p>Sensitization leading to severe anaemia in subsequent pregnancies</p> Signup and view all the answers

    What role does FcγRn play in relation to maternal antibodies and the fetus?

    <p>It allows the transfer of certain antibodies from mother to infant</p> Signup and view all the answers

    What is the consequence of the immune-complexed IgG binding to FcγRIIB?

    <p>It inhibits cell functions and can induce apoptosis</p> Signup and view all the answers

    Which pathology can be prevented by administering anti-Rh Ig after delivery?

    <p>Erythroblastosis fetalis</p> Signup and view all the answers

    What happens to a baby with erythroblastosis fetalis due to Rh incompatibility?

    <p>The baby experiences increased bilirubin levels and potential anaemia</p> Signup and view all the answers

    Which blood group represents individuals who inherited both enzymes for adding α-N-acetyl-galactosamine and α-D-galactose?

    <p>AB group</p> Signup and view all the answers

    What is the primary function of anti-A and anti-B antibodies?

    <p>React against sugars present in bacterial cell walls</p> Signup and view all the answers

    What is true about IgE in serum?

    <p>It can persist for years when bound to FcεRI</p> Signup and view all the answers

    Which statement best describes the interaction between IgE and tetrameric FcεRI?

    <p>Activation of ITAM sequences occurs after antigen crosslinking</p> Signup and view all the answers

    Which blood group is characterized by the absence of both enzymes for adding sugars to substance H?

    <p>O group</p> Signup and view all the answers

    What type of antibodies are primarily involved in the response against carbohydrate antigens?

    <p>IgM antibodies</p> Signup and view all the answers

    Where are tetrameric FcεRI receptors primarily located in the body?

    <p>On basophils and mast cells beneath the skin and mucosa</p> Signup and view all the answers

    What can be inferred about T cells from the information provided?

    <p>They do not deliver isotype switching signals</p> Signup and view all the answers

    Where does affinity maturation occur within the germinal centre?

    <p>In the light area with centrocytes</p> Signup and view all the answers

    What is the role of the enzyme AID in the germinal centre?

    <p>To deaminate cytosine to uracil</p> Signup and view all the answers

    What happens to B cells during isotype switching?

    <p>They change the class of antibodies produced</p> Signup and view all the answers

    Which process allows only B cells producing high-affinity antibodies to survive?

    <p>Affinity maturation</p> Signup and view all the answers

    What distinguishes centroblasts from centrocytes in terms of their cellular state?

    <p>Centroblasts are actively proliferating; centrocytes have exited the cell cycle</p> Signup and view all the answers

    Which DNA repair process can occur when uridine is detected during mismatch repair?

    <p>Base excision repair</p> Signup and view all the answers

    What is the characteristic histological appearance of centroblasts during proliferation?

    <p>Dark staining due to abundant nuclear content</p> Signup and view all the answers

    Which statement best describes the outcome of hypermutation in centroblasts?

    <p>It enhances the affinity of antibodies for the specific antigen</p> Signup and view all the answers

    Study Notes

    Antibody Subtypes

    • Antibodies (immunoglobulins) are crucial for immunity and come in various subtypes (isotypes), each with distinct properties and roles. These five main subtypes are IgG, IgM, IgA, IgE, and IgD.
    • IgG is the most abundant antibody, comprising about 80% of serum immunoglobulins. It's monomeric, long-lived (about 20 days), and can cross the placenta. It's involved in various immune responses.
    • IgM is the first antibody produced in response to an infection. It's a large pentameric structure and is relatively short-lived (5-10 days). It's crucial for complement activation and is found in blood and mucous membranes. It cannot cross the placenta.
    • IgA is the most abundant antibody in secretions (tears, saliva, milk). It's typically a dimeric structure (but can also be monomeric) that's important for mucosal immunity to prevent pathogenic invasion. It is particularly significant in protecting external surfaces such as the gut and respiratory tract. It's also short-lived.
    • IgE is involved in allergic reactions and parasitic infections. It's monomeric and is found in very low concentrations in serum. When IgE attaches to specialized Fc receptors on mast cells and basophils, it triggers the release of inflammatory mediators.
    • IgD is predominantly a membrane-bound antibody, acting as a B cell receptor (BCR). It's monomeric and is found in low levels in the serum. Its exact function in vivo is less well understood than other antibody types.

    Antibody Structures

    • Antibodies are composed of two heavy chains and two light chains, forming a Y-shaped structure.
    • The tips of the Y (variable regions) are responsible for binding to specific antigens.
    • The remaining portions (constant regions) of the antibody dictates which other cellular components of the immune system the antibody will activate.
    • The hinge region provides flexibility within the antibody structure. This allows it to bind antigens that are spaced far apart.
    • The constant region (Fc) of the antibody determines the antibody class and mediates interactions with components of the immune system (e.g., complement).
    • Some enzymes (papain and pepsin) can cut the antibody into fragments.
    • These fragmented pieces can be used to study antibody fragments.

    Antibody Activation and Affinity

    • Different kinds of antigens activate antibodies in different ways.
    • T-dependent antigen response requires T-helper cells, which allows for somatic mutation and class switching resulting in a high-affinity antibody response. Memory B cells are generated.
    • T-independent antigen response does not require T cells and generates antibodies with lower affinity and short-lived plasma cells.
    • Affinity is the strength of the binding between an antibody and an antigen.
    • A higher affinity results in a greater antibody response.
    • Avidity is the overall strength of binding in an antibody with multiple binding sites. A higher avidity results in stronger overall responses. The number of antigens bound strongly increases with a higher avidity.

    Antibody Functions

    • Antibodies can directly neutralize pathogens (toxins and viruses).
    • Antibodies can act as opsonins, enhancing phagocytosis by immune cells.
    • Antibodies can trigger complement activation, leading to pathogen destruction.
    • Antibody-dependent cell-mediated cytotoxicity (ADCC) in which cytotoxin-armed immune cells kill pathogens coated in antibodies.
    • Antibodies can opsonize pathogens, making them more readily ingested by phagocytic immune cells.

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    Related Documents

    Immunology Lesson 13, 14 PDF

    Description

    Test your knowledge on different antibody subtypes, including their structures, functions, and roles in immune responses. Dive into the details of IgG, IgM, IgA, IgE, and IgD to understand their significance in immunity.

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