Introduction to Immunology
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Questions and Answers

What is the primary role of cDC1 dendritic cells?

  • Activate CD4+ T cells
  • Specialize in cross-presentation to CD8+ T cells (correct)
  • Differentiate from monocytes during inflammation
  • Produce large amounts of type I interferons

    • Which dendritic cell type plays a significant role in antiviral immunity by producing large amounts of type I interferons?

  • Plasmacytoid dendritic cells (correct)
  • Langerhans cells
  • Monocyte-derived dendritic cells
  • Conventional dendritic cells

    • Which of the following statements correctly describes Langerhans cells?

  • They are derived from bone marrow precursor cells.
  • They are the most numerous DC subset in lymphoid organs.
  • They primarily activate CD8+ T cells.
  • They present self-antigens to induce tolerance. (correct)

    • What distinguishes monocyte-derived dendritic cells (moDCs) from other types of dendritic cells?

    <p>They can differentiate from monocytes in inflammatory conditions.</p> Signup and view all the answers

    Which dendritic cell subset is primarily responsible for orchestrating a broader immune response by activating CD4+ T cells?

    <p>cDC2</p> Signup and view all the answers

    What is the role of C-type lectin receptors (CLRs) in the immune response?

    <p>They recognize carbohydrate structures and promote phagocytosis.</p> Signup and view all the answers

    Which of the following ligands is specifically recognized by Dectin-1?

    <p>β-glucans</p> Signup and view all the answers

    Which type of immune cell primarily expresses the mannose receptor?

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

    What is the function of NOD-like receptors (NLRs) in the immune system?

    <p>Sense intracellular pathogens and stress signals.</p> Signup and view all the answers

    What cytokines are associated with the signaling pathways involving NLRs?

    <p>IL-6 and IL-23</p> Signup and view all the answers

    Which NOD receptor is specifically activated by muramyl dipeptide (MDP)?

    <p>NOD2</p> Signup and view all the answers

    What does the formation of inflammasomes lead to?

    <p>Activation of caspase-1 and cytokine maturation.</p> Signup and view all the answers

    Which of the following statements is true regarding NLRP3?

    <p>It forms multiprotein complexes for cytokine activation.</p> Signup and view all the answers

    What is the primary function of phagocytosis in the immune response?

    <p>Engulfment of larger particles like bacteria</p> Signup and view all the answers

    What triggers the maturation process of dendritic cells?

    <p>Exposure to PAMPs and inflammatory cytokines</p> Signup and view all the answers

    Which chemokines are specifically recognized by CCR7 on dendritic cells?

    <p>CCL19 and CCL21</p> Signup and view all the answers

    What function do costimulatory molecules like CD80 and CD86 serve in T cell activation?

    <p>They provide the necessary second signal for T cell activation</p> Signup and view all the answers

    What happens to dendritic cells after they mature?

    <p>They express CCR7 for migration to lymph nodes</p> Signup and view all the answers

    What is the role of cytokines such as IL-12 and IFN-alpha in the immune response?

    <p>They shape the adaptive immune response</p> Signup and view all the answers

    What is a consequence of dendritic cells presenting self-antigens to T cells?

    <p>Activation of regulatory T cells or T cell death</p> Signup and view all the answers

    How do naive T cells localize in lymph nodes in relation to dendritic cells?

    <p>By utilizing CCR7 to migrate towards chemokines</p> Signup and view all the answers

    What distinguishes the innate immune system's specificity from that of the adaptive immune system?

    <p>Innate specificity is for shared molecules of related microbes.</p> Signup and view all the answers

    Which type of immune cells are primarily involved in the innate immune response?

    <p>Macrophages and neutrophils</p> Signup and view all the answers

    What is a characteristic feature of the adaptive immune system?

    <p>It generates specific antigen receptors through somatic recombination.</p> Signup and view all the answers

    Which of the following accurately describes the memory function of the immune system?

    <p>The adaptive immune system has a well-defined memory mechanism.</p> Signup and view all the answers

    What role do MHC molecules play in the immune system?

    <p>They help in presenting antigens to T cells.</p> Signup and view all the answers

    What triggers the release of immune cells from the bone marrow?

    <p>Chemical signals from damaged tissues</p> Signup and view all the answers

    How does the diversity of the innate immune system compare to that of the adaptive immune system?

    <p>Adaptive possesses a very high diversity.</p> Signup and view all the answers

    Which barrier is considered a part of the innate immune system?

    <p>Skin and mucosal epithelia</p> Signup and view all the answers

    Which immune response is primarily managed by lymphocytes?

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

    Which type of immune cells are involved in the sequestration and destruction of pathogens?

    <p>Neutrophils and macrophages</p> Signup and view all the answers

    What describes the physiological barriers of the innate immune system?

    <p>They function as a primary defense against pathogens.</p> Signup and view all the answers

    What does the term 'pathogen recognition receptors' refer to in the context of the immune system?

    <p>Molecules that detect foreign pathogens.</p> Signup and view all the answers

    How do innate lymphoid cells differ from conventional lymphocytes?

    <p>Innate lymphoid cells do not produce antibodies.</p> Signup and view all the answers

    What is the primary function of NK cells in the immune system?

    <p>To kill infected or cancerous cells</p> Signup and view all the answers

    What happens during T cell development, also known as T lymphopoiesis?

    <p>T cells undergo differentiation in the thymus.</p> Signup and view all the answers

    What is the primary function of MHC molecules?

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

    Which type of MHC molecule primarily presents intracellular antigens?

    <p>MHC class I</p> Signup and view all the answers

    What structural component is crucial for MHC class II molecules?

    <p>Two extracellular α-domains</p> Signup and view all the answers

    Which of the following describes the binding groove of MHC class II molecules?

    <p>Open-ended, allowing for longer peptides</p> Signup and view all the answers

    What is the role of MHC class III genes?

    <p>Producing immune-related proteins like cytokines</p> Signup and view all the answers

    What feature contributes to the high polymorphism of MHC-I genes?

    <p>Different alleles within the population</p> Signup and view all the answers

    How does heterozygosity affect antigen presentation?

    <p>It enhances the ability to respond to diverse pathogens</p> Signup and view all the answers

    Which of the following MHC genes is associated with autoimmune diseases?

    <p>HLA-B27</p> Signup and view all the answers

    What is the significance of maternal and paternal allele expression in MHC genes?

    <p>It increases the genetic diversity of antigen presentation</p> Signup and view all the answers

    Which MHC class primarily interacts with CD4+ helper T cells?

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

    What is the characteristic arrangement of MHC class I molecules?

    <p>Three extracellular domains and a transmembrane region</p> Signup and view all the answers

    What is the difference between MHC class I and class II in terms of antigen source?

    <p>Class I presents intracellular antigens, while class II presents extracellular antigens</p> Signup and view all the answers

    What defines the peptide-binding cleft of MHC class I molecules?

    <p>Constructed from α1 and α2 domains and interacts with CD8</p> Signup and view all the answers

    Which statement accurately describes the role of MHC molecules in the immune system?

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

    Study Notes

    Introduction to Immunology

    • Immunology studies the body's defense mechanisms against injuries, infectious organisms, or foreign substances.
    • Two main types of immune systems: innate and adaptive.

    Innate Immune System

    • Low specificity, recognizing molecules shared by groups of microbes and molecules produced by damaged host cells.
    • Low diversity, molecules encoded by inherited genes.
    • Limited memory.
    • Barriers include skin, mucosal epithelia, antimicrobial molecules, and secreted proteins like complement.
    • Cells include phagocytes (macrophages, neutrophils), dendritic cells, NK cells, mast cells, and innate lymphoid cells.

    Adaptive Immune System

    • High specificity, targeting many different microbial and non-microbial antigens.
    • High diversity, antigen receptors generated by somatic recombination of gene segments in lymphocytes.
    • Possesses memory.
    • Cells include lymphocytes: B cells and T cells.

    Immune Response Phases

    • Phase 1: Neighbouring cells enter an antiviral state, preparing for potential infection.
    • Phase 2: C-type lectin receptors (CLRs) recognize carbohydrate structures on pathogens (mannose, glucans, fucose).
    • Phase 3: NOD-like receptors (NLRs) sense intracellular PAMPs and DAMPs, playing a vital role in inflammation and immune homeostasis.
    • Phase 4: Dendritic cells (DCs) capture protein antigens and present them to T cells.

    C-Type Lectin Receptors (CLRs)

    • Membrane-bound receptors, mainly on macrophages and dendritic cells.
    • Recognize carbohydrate structures on pathogens, promoting phagocytosis and initiating immune signaling.
    • Examples: Dectin-1 (β-glucans), Mannose receptor (mannose and fucose).
    • Signaling pathway: Syk kinase/CARD9, NF-κB, AP-1, leading to pro-inflammatory cytokines and immune cell recruitment.

    NOD-Like Receptors (NLRs)

    • Cytoplasmic receptors detecting microbial components and stress signals.
    • Located on endothelial cells, macrophages, dendritic cells, but not neutrophils.
    • Examples: NOD1 (DAP), NOD2 (muramyl dipeptide).
    • Signaling pathway: NF-κB or inflammasome formation, leading to pyroptosis and the release of pro-inflammatory cytokines.
    • NOD2 also influences type I interferon production.
    • NLRP3 forms inflammasomes, activating caspase-1, leading to IL-1β and IL-18 maturation.

    Dendritic Cells (DCs)

    • Major types: Classical/Conventional DCs (cDCs), Plasmacytoid DCs, Monocyte-derived DCs (moDCs), Langerhans cells.
    • cDCs: Most numerous DC subset, involved in presenting protein antigens to T cells.
      • cDC1: Specializes in cross-presentation of antigens to CD8+ T cells, critical for anti-viral and anti-tumor immunity.
      • cDC2: Activates CD4+ T cells (helper T cells) and orchestrates the broader immune response.
    • Plasmacytoid DCs: resemble plasma cells, main producers of IFN I, involved in antiviral immunity.
    • moDCs: Differentiate from monocytes in inflammatory conditions, play a role in inflammation and infection.
    • Langerhans cells: Found in epidermis, present antigens to CD4+ T cells, inducing tolerance or activating immune responses.
    • DC Maturation: Upon exposure to pathogens or inflammatory cytokines, DCs undergo a maturation process characterized by:
      • Upregulation of MHC class I & II molecules for antigen presentation.
      • Upregulation of costimulatory molecules (CD80, CD86, CD40) for efficient T cell priming.
      • Secretion of cytokines (IL-12, IL-6, IFN-alpha) to shape the adaptive immune response.
    • DC Migration: DCs lose their phagocytic ability and gain migratory properties, expressing chemokine receptors like CCR7, enabling them to migrate to lymph nodes.

    Major Histocompatibility Complex (MHC) Molecules

    • Proteins on cell surfaces, crucial for the immune system's antigen recognition and response.
    • Functions:
      • Bind and present peptide antigens to T cells.
      • Distinguish self from non-self.
    • Types:
      • MHC Class I: Presents intracellular antigens to CD8+ cytotoxic T cells, found on most nucleated cells.
      • MHC Class II: Presents extracellular antigens to CD4+ helper T cells, found on antigen-presenting cells (APCs).
      • MHC Class III: Encodes immune-related proteins like complement proteins and cytokines.

    MHC Genes

    • Located in the human leukocyte antigen (HLA) complex on chromosome 6.
      • MHC-I genes (HLA-A, HLA-B, HLA-C): Highly polymorphic, contributing to genetic diversity.
      • MHC-II genes (HLA-DP, HLA-DQ, HLA-DR): Significant polymorphism, allowing for various combinations.
    • Characteristics:
      • Highly polymorphic, allowing individual variation in antigen presentation.
      • Multiple MHC genes expressed in each individual, inherited as haplotypes.
      • Maternal and paternal alleles expressed, further enhancing diversity.
      • Heterozygosity (having two different alleles) is beneficial, providing broader antigen-presenting capabilities.
    • Disease Association: Specific MHC alleles can be associated with particular diseases, like HLA-B27 with ankylosing spondylitis.

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    Description

    This quiz covers the fundamental concepts of immunology, focusing on the body's defense mechanisms against infections and foreign substances. It distinguishes between the innate and adaptive immune systems, detailing their characteristics and components. Test your understanding of immune responses and the cellular actors involved!

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