B Cell & T Cell Receptors Quiz
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Questions and Answers

What is the principal function of cellular receptors in the immune system?

  • To facilitate antigen processing and presentation
  • To regulate lymphocyte maturation
  • To detect external stimuli and trigger responses (correct)
  • To produce antigens

    • What distinguishes B and T lymphocytes in terms of antigen recognition?

  • Response to different types of antigens
  • Location of maturation within the body
  • Expression of membrane-bound antibodies and T cell receptors (correct)
  • Expression of different cytokines

    • Why is it important for antigen receptors of lymphocytes to be able to distinguish between many closely related chemical structures?

  • To eliminate harmful pathogens
  • To preserve useful specificities (correct)
  • To regulate immune responses
  • To avoid self reactivity

    • What does clonally distributed mean in the context of antigen receptors of lymphocytes?

    <p>Each lymphocyte clone is specific for a distinct antigen and has a unique receptor</p> Signup and view all the answers

    Which portion of the antibody molecule is responsible for effector functions?

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

    What contributes most to antigen binding due to its great variability?

    <p>CDR3</p> Signup and view all the answers

    Which type of Ig heavy chain protein results in a membrane-bound antibody on naive B cells?

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

    What is the core structure of antibody molecules containing?

    <p>Two identical antigen-binding sites</p> Signup and view all the answers

    Which process allows B cells to change their heavy-chain production and secrete various isotypes?

    <p>Heavy-chain class switching</p> Signup and view all the answers

    What is the structure of antibodies, such as IgG and IgM, consisting of?

    <p>Heavy and light chains, and regions for antigen recognition and effector functions</p> Signup and view all the answers

    What are the functionally distinct portions of antibodies identified through proteolysis?

    <p>Fab regions and Fc regions</p> Signup and view all the answers

    Which portion of the antibody molecule contains antigen-binding sites?

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

    How many identical antigen-binding sites does the core structure of an antibody molecule contain?

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

    What is the process by which B cells can stimulate the production of various heavy-chain isotypes upon antigen exposure?

    <p>Class switching</p> Signup and view all the answers

    Which portion of the antibody molecule contains constant domains responsible for effector functions?

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

    What are the antigens receptors on naive B cells primarily composed of?

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

    What is the average half-life of IgG antibodies?

    <p>3-4 weeks</p> Signup and view all the answers

    What are the two types of light chains that contribute to forming the antigen-binding surface of antibodies?

    <p>κ and λ</p> Signup and view all the answers

    What are epitopes?

    <p>Parts of antigens recognized by antibodies</p> Signup and view all the answers

    How is antibody affinity measured?

    <p>By the strength of binding between an antibody and an epitope</p> Signup and view all the answers

    Which antibody isotype is primarily involved in defense against microbes?

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

    What is the typical number of antigen-binding sites for each antibody molecule?

    <p>8-10</p> Signup and view all the answers

    What type of epitopes are contiguous amino acid sequences?

    <p>Linear epitopes</p> Signup and view all the answers

    What is the phenomenon called when antibodies produced against one antigen can bind to structurally similar antigens?

    <p>Cross-reaction</p> Signup and view all the answers

    What contributes to forming the antigen-binding surface of antibodies?

    <p>Light chain</p> Signup and view all the answers

    What does antibody avidity refer to?

    <p>The combined binding strength of multiple antigen-antibody interactions</p> Signup and view all the answers

    What type of interactions do antibodies use to bind to antigens?

    <p>Ionic interactions</p> Signup and view all the answers

    What are the distinct features, shapes, and functions associated with different antibody isotypes called?

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

    What is the main function of the immune repertoire?

    <p>To transmit diverse signals despite recognizing similar antigens</p> Signup and view all the answers

    What is the specificity of B cell antigen receptors?

    <p>Recognition of diverse macromolecules and smaller chemical structures</p> Signup and view all the answers

    What ensures the specificity of T cell antigen receptors for infected or tumor cells?

    <p>Recognition of peptides bound to MHC molecules</p> Signup and view all the answers

    What is the function of complementarity-determining regions (CDRs) in antigen receptor polypeptides?

    <p>Antigen recognition</p> Signup and view all the answers

    What is the result of antigen binding to the extracellular portions of antigen receptors?

    <p>Signaling cascades and gene transcription</p> Signup and view all the answers

    What is the composition of the B cell receptor (BCR) complex?

    <p>Invariant membrane proteins associated with the receptors</p> Signup and view all the answers

    What is the function of T cell receptors (TCR) complex?

    <p>Recognition of peptides bound to MHC molecules</p> Signup and view all the answers

    What leads to lymphocyte division, differentiation, effector functions, or death following antigen recognition?

    <p>Intracellular signals associated with recognition</p> Signup and view all the answers

    What distinguishes B cell and T cell antigen receptors in terms of their antigen recognition properties?

    <p>Recognition of peptides bound to MHC molecules</p> Signup and view all the answers

    What is the role of variable regions in antigen receptor polypeptides?

    <p>To contribute to antigen recognition</p> Signup and view all the answers

    What do intracellular signals associated with recognition lead to?

    <p>Lymphocyte division</p> Signup and view all the answers

    What is the primary difference in the form of antibodies and TCRs?

    <p>Antibodies exist as both membrane-bound antigen receptors and secreted proteins, while TCRs only exist as membrane receptors on T cells.</p> Signup and view all the answers

    Which proteins are associated with the signaling functions of BCRs?

    <p>Ig alpha and Ig beta</p> Signup and view all the answers

    What is the primary function of secreted antibodies?

    <p>Performing effector functions like complement fixation and phagocyte binding</p> Signup and view all the answers

    How is antigen recognition mediated by antibodies' variable regions?

    <p>Through three CDRs from V sub H and three CDRs from V sub L</p> Signup and view all the answers

    What is the typical requirement for BCR signaling?

    <p>Binding of multiple receptors to adjacent antigen molecules</p> Signup and view all the answers

    What is the approximate potential for distinct specificities in BCRs?

    <p>$10^{11}$</p> Signup and view all the answers

    Which type of antigens are recognized by TCRs?

    <p>Mainly peptides displayed by MHC molecules on APCs</p> Signup and view all the answers

    What is the affinity range of antigen binding for TCRs?

    <p>$10^{-5}$ to $10^{-7}$ M</p> Signup and view all the answers

    What are the effector functions mediated by TCRs?

    <p>None</p> Signup and view all the answers

    What form do TCRs primarily exist in?

    <p>Membrane receptors on T cells</p> Signup and view all the answers

    Which region of antibodies recognizes microbial antigens?

    <p>Variable domains</p> Signup and view all the answers

    What is the primary function of membrane-bound BCRs on B cells?

    <p>Acting as antigen receptors and mediating signaling functions</p> Signup and view all the answers

    Study Notes

    • Antigen receptors and associated signaling proteins form BCR and TCR complexes.
    • BCR typically requires binding of multiple receptors to adjacent antigen molecules for signaling.
    • Antibodies:
      • Membrane form: Ig alpha, Ig beta, and antigen bound to plasma membrane leading to signal transduction.
      • Secreted form: Secreted antibodies performing effector functions like complement fixation and phagocyte binding.
      • Types of antigens recognized: macromolecules (proteins, polysaccharides, lipids, nucleic acids), small chemicals, conformational and linear epitopes.
      • Diversity: each clone has a unique specificity, potential for approximately 10^11 distinct specificities.
      • Antigen recognition is mediated by variable (V) regions of heavy and light chains.
      • Antigen binding site: made up of three CDRs from V sub H and three CDRs from V sub L.
      • Affinity of antigen binding: Kd 10^-7 to 10^-11 M, average affinity increases during immune responses.
      • Signaling functions are mediated by proteins (Ig alpha and Ig beta) associated with membrane Ig.
      • Effector functions are mediated by constant (C) regions of secreted Ig.
      • Changes in constant regions: heavy chain class switching, change from membrane to secretory Ig.
    • TCRs:
      • Membrane form: antigen bound to MHC above and TCR below, CDR3 and zeta receptors for signal transduction.
      • Secreted form: none.
      • Types of antigens recognized: mainly peptides displayed by MHC molecules on APCs, linear epitopes.
      • Diversity: each clone has a unique specificity, potential for approximately 10^16 distinct specificities.
      • Antigen recognition is mediated by variable (V) regions of alpha and beta chains.
      • Antigen binding site: made up of three CDRs from V alpha and three CDRs from V beta.
      • Affinity of antigen binding: Kd 10^-5 to 10^-7 M, no change during immune responses.
      • Signaling functions are mediated by proteins (CDR3 and zeta) associated with the TCR.
      • Effector functions are not mediated by TCRs.
    • Antibodies exist as membrane-bound antigen receptors on B cells and as secreted proteins (immunoglobulins), providing protection against microbes.
    • Antibodies recognize microbial antigens through their variable domains, and their constant regions bind to other molecules for effector functions.
    • TCRs exist only as membrane receptors on T cells, involved solely in antigen recognition and T cell activation.

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    Description

    Test your knowledge of B cell receptors (BCRs) and T cell receptors (TCRs) with this quiz. Explore the characteristics and signaling proteins associated with antigen-recognizing molecules.

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