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

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

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

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

<p>CDR3 (C)</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 (D)</p> Signup and view all the answers

What is the core structure of antibody molecules containing?

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

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

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

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

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

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

<p>Two (A)</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 (C)</p> Signup and view all the answers

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

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

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

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

What is the average half-life of IgG antibodies?

<p>3-4 weeks (A)</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 (C)</p> Signup and view all the answers

What are epitopes?

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

How is antibody affinity measured?

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

Which antibody isotype is primarily involved in defense against microbes?

<p>IgG (A)</p> Signup and view all the answers

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

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

What type of epitopes are contiguous amino acid sequences?

<p>Linear epitopes (D)</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 (A)</p> Signup and view all the answers

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

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

What does antibody avidity refer to?

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

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

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

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

<p>Allotypes (C)</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 (D)</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 (B)</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 (D)</p> Signup and view all the answers

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

<p>Antigen recognition (C)</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 (D)</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 (D)</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 (C)</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 (D)</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> (C) Signup and view all the answers

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

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

What do intracellular signals associated with recognition lead to?

<p>Lymphocyte division (A)</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. (A)</p> Signup and view all the answers

Which proteins are associated with the signaling functions of BCRs?

<p>Ig alpha and Ig beta (B)</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 (B)</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 (D)</p> Signup and view all the answers

What is the typical requirement for BCR signaling?

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

What is the approximate potential for distinct specificities in BCRs?

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

Which type of antigens are recognized by TCRs?

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

What is the affinity range of antigen binding for TCRs?

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

What are the effector functions mediated by TCRs?

<p>None (C)</p> Signup and view all the answers

What form do TCRs primarily exist in?

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

Which region of antibodies recognizes microbial antigens?

<p>Variable domains (B)</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 (A)</p> Signup and view all the answers

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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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