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B-Cell Development and Activation
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B-Cell Development and Activation

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Questions and Answers

What is the primary function of TH cells in B cell response?

  • To filter antigens from tissue spaces
  • To activate B cells directly
  • To secrete IgM and IgG isotypes
  • To play an essential role in B cell response (correct)

    • What happens to memory B cells formed during a primary response?

  • They differentiate into naive B cells
  • They undergo apoptosis and die
  • They stop dividing and enter the G0 phase of the cell cycle (correct)
  • They continue to divide and undergo clonal expansion

    • Where do antigen-antibody complexes enter the lymph node?

  • Associated with antigen transporting cells (correct)
  • Through lymphatic vessels
  • Through blood vessels
  • Through the spleen

    • What is the result of antigen-mediated B-cell activation in lymph nodes?

    <p>Proliferation of B cells at the edges of the T-cell–rich zone</p> Signup and view all the answers

    What is the result of antibody-mediated suppression on the humoral response?

    <p>Low humoral response and inadequate production of memory cells</p> Signup and view all the answers

    Why are certain vaccines not administered to infants before the age of 1 year?

    <p>Because the level of naturally acquired maternal IgG is high</p> Signup and view all the answers

    What is the primary site of B cell activation?

    <p>Lymph nodes</p> Signup and view all the answers

    What is the primary function of antibodies in the humoral immune response?

    <p>To recognize and bind to antigens</p> Signup and view all the answers

    What is the time frame for germinal center formation?

    <p>7-10 days</p> Signup and view all the answers

    What is the primary function of germinal centers?

    <p>To undergo intense proliferation and differentiation</p> Signup and view all the answers

    What is the characteristic of a primary response to antigen?

    <p>A lag phase followed by clonal expansion</p> Signup and view all the answers

    What is the result of B-cell differentiation in germinal centers?

    <p>Formation of plasma and memory B cells</p> Signup and view all the answers

    What is the result of the immune system encountering an antigen?

    <p>Either an immune response or tolerance</p> Signup and view all the answers

    What is the role of antigen-antibody complexes in lymph nodes?

    <p>To enter the lymph node and trigger a humoral immune response</p> Signup and view all the answers

    Why is it necessary to regulate the immune effector response?

    <p>To prevent damage to host tissues</p> Signup and view all the answers

    What happens to naive B cells during a primary response?

    <p>They undergo clonal expansion and differentiation</p> Signup and view all the answers

    Where do Progenitor B Cells proliferate?

    <p>Bone Marrow</p> Signup and view all the answers

    What is required for the development of immature B cells into precursor B cells?

    <p>Heavy chain rearrangement</p> Signup and view all the answers

    What type of antigens require direct contact with TH cells?

    <p>Thymus-dependent (TD) antigens</p> Signup and view all the answers

    What is the characteristic of TI-1 antigens?

    <p>They are multivalent and bind to both Ig and innate receptors</p> Signup and view all the answers

    What is the result of TI-1 antigen binding to B cells?

    <p>A polyclonal, antibody-secreting response</p> Signup and view all the answers

    What is the role of stromal cells in the bone marrow?

    <p>They secrete IL-7 to help B cell development</p> Signup and view all the answers

    What is the characteristic of an immature B cell?

    <p>It is committed to antigenic specificity and produces IgM</p> Signup and view all the answers

    What is required for a B cell to be fully functional?

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

    What is the result of active immunization?

    <p>Formation of memory cells</p> Signup and view all the answers

    What is a key consideration in designing vaccines for active immunization?

    <p>The need to develop immunologic memory</p> Signup and view all the answers

    What is the purpose of attenuating microorganisms in vaccine development?

    <p>To allow for transient growth within an inoculated host</p> Signup and view all the answers

    What is a characteristic of inactivated whole pathogenic organisms used in vaccine development?

    <p>They are inactivated by heat or chemical means</p> Signup and view all the answers

    What is the effect of heat inactivation on proteins?

    <p>It denatures them</p> Signup and view all the answers

    What type of immune response is elicited by inactivated whole pathogenic organisms?

    <p>Humoral immune response</p> Signup and view all the answers

    Why are booster doses required for inactivated whole pathogenic organisms?

    <p>To maintain immunity over time</p> Signup and view all the answers

    What is the goal of vaccine designers when developing a vaccine?

    <p>To recognize the importance of immunologic memory</p> Signup and view all the answers

    Which type of cells express the highest levels of class I MHC molecules?

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

    What is the main function of antigen-presenting cells?

    <p>To present antigens to T cells</p> Signup and view all the answers

    Which type of MHC molecules are expressed constitutively by antigen-presenting cells?

    <p>Class II MHC molecules</p> Signup and view all the answers

    What is the term for the process of degrading protein antigens into peptides that can be presented by MHC molecules?

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

    What type of cells are restricted to recognizing antigen presented by MHC Class II molecules?

    <p>CD4+ TH cells</p> Signup and view all the answers

    What is the term for the complex formed by the association of a peptide with an MHC molecule?

    <p>Peptide-MHC complex</p> Signup and view all the answers

    What type of antigens are processed and presented by Class I MHC molecules?

    <p>Endogenous antigens</p> Signup and view all the answers

    What is the term for the cells that are killed by cytotoxic T cells?

    <p>Target cells</p> Signup and view all the answers

    Study Notes

    B-Cell Development

    • Progenitor B cells proliferate in the bone marrow, where they develop into immature B cells with the help of stromal cells and IL-7.
    • Pro-B cells undergo heavy chain rearrangement, while pre-B cells undergo light chain rearrangement.
    • Immature B cells are committed to antigenic specificity and produce IgM, but they are not fully functional until they express both IgM and IgD on their membrane.

    B-Cell Activation and Proliferation

    • After export from the bone marrow, B cells undergo activation, proliferation, and differentiation in the periphery, requiring antigen.
    • Thymus-independent (TI) antigens, such as lipopolysaccharide (LPS), can activate B cells through innate receptors, leading to a polyclonal response.
    • Thymus-dependent (TD) antigens require direct contact with TH cells for B cell activation.

    B-Cell Activation

    • TH cells play an essential role in B cell response, and interaction between B cells and T cells occurs in the lymph nodes.
    • In vivo, B cells are activated in peripheral lymphoid organs, such as the spleen and lymph nodes, where they differentiate into plasma cells secreting IgM and IgG.

    Germinal Centers and Antigen-Induced B-Cell Differentiation

    • Germinal centers arise within 7-10 days after initial exposure to thymus-dependent antigen in lymph nodes.
    • Three important B-cell differentiation events occur in germinal centers: affinity maturation, class switching, and formation of plasma and memory B cells.

    The Humoral Response

    • The humoral immune response is carried out by antibodies produced by activated B cells.
    • Primary and secondary responses differ significantly, with primary responses characterized by a lag phase and secondary responses resulting in a more rapid and robust response.

    Regulation of the Immune Effector Response

    • Humoral and cell-mediated branches must be heavily regulated to prevent over-activation.
    • The immune system can either develop an immune response or enter a state of tolerance upon encountering an antigen.
    • MHC restriction is important, with CD8+ Tc cells recognizing antigen presented by MHC Class I molecules and CD4+ TH cells recognizing antigen presented by MHC Class II molecules.

    Antigen Processing and Presentation

    • Antigen processing involves the degradation of protein antigens into peptides, which then associate with MHC molecules and are transported to the membrane for display.
    • Class I MHC molecules bind peptides derived from endogenous antigens, while Class II MHC molecules bind peptides derived from exogenous antigens.

    Designing Vaccines for Active Immunization

    • Several factors must be considered when developing a successful vaccine, including the activation of the humoral or cell-mediated branch and the development of immunologic memory.
    • Whole-organism vaccines can be attenuated to lose their pathogenicity but retain their capacity for transient growth, or inactivated to elicit a humoral immune response.

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    Description

    Learn about the development and activation of B cells, including their proliferation in the bone marrow, antigenic specificity, and IgM and IgD expression.

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