Adaptive Immunology questions
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Questions and Answers

What is the primary consequence of CD8+ T cells interacting with MHC class I molecules?

  • Increase in antibody production
  • Activation of helper T cells
  • Release of cytokines
  • Death of the presenting cell (correct)

    • Which cytokine is primarily associated with the activation of helper T cells when they recognize MHC class II?

  • IL-10
  • IL-2 (correct)
  • TNF-alpha
  • IFN-gamma

    • Which of the following correctly describes the structure of TCR?

  • One heavy and one light chain only
  • Four identical chains held by peptide bonds
  • Two chains typically marked as alpha and beta (correct)
  • Two identical heavy and two identical light chains

    • Which MHC class molecules are known to be expressed on all nucleated cells?

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

    What is the main function of dendritic cells in the immune response?

    <p>Act as professional antigen presenting cells</p> Signup and view all the answers

    The generation of diversity in TCR and BCR is primarily a result of which process?

    <p>Recombination of gene segments</p> Signup and view all the answers

    Which of the following genes are classified under MHC class II in humans?

    <p>HLA-DPA1, HLA-DPB1, HLA-DQA1</p> Signup and view all the answers

    What happens to immature T cells that recognize self-peptides in the thymus?

    <p>They undergo apoptosis in a process called negative selection</p> Signup and view all the answers

    What role do dendritic cells play in the adaptive immune response?

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

    Which of the following best describes MHC Class II molecules?

    <p>They present exogenous antigens to CD4+ T helper cells.</p> Signup and view all the answers

    What is a key feature of T Cell Receptor (TCR) diversity?

    <p>TCR diversity is mainly generated through V(D)J recombination.</p> Signup and view all the answers

    Which statement is true regarding MHC Class I molecules?

    <p>They consist of an alpha chain and a beta-2 microglobulin.</p> Signup and view all the answers

    What is the function of T helper cells during T cell activation?

    <p>They activate B cells and cytotoxic T cells.</p> Signup and view all the answers

    Which class of antibodies is typically produced first in an immune response?

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

    Which of the following mechanisms do natural killer (NK) cells utilize to recognize antibody-coated cells?

    <p>They utilize Fc receptor CD16 for recognition.</p> Signup and view all the answers

    What occurs during the process of isotype switching in B cells?

    <p>B cells change the class of antibody they produce.</p> Signup and view all the answers

    What are the three signals required for the activation of T cells?

    <p>TCR - Antigen recognition, Co-stimulation by presenting cell, Cytokines</p> Signup and view all the answers

    Which signal is NOT involved in the activation of B cells?

    <p>Cytokines produced by B cells</p> Signup and view all the answers

    What is the primary function of MHC Class II in B cell activation?

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

    Which component is NOT a part of the receptor on T cells?

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

    Which statement about dendritic cells is true in the context of T cell activation?

    <p>They present antigens to T cells through MHC Class II</p> Signup and view all the answers

    What is the role of CD40L in B cell activation?

    <p>To facilitate co-stimulation with CD40 on B cells</p> Signup and view all the answers

    What distinguishes MHC Class I structure from MHC Class II?

    <p>MHC Class I has a β2-microglobulin component</p> Signup and view all the answers

    During the activation of B cells, what happens after antigen recognition by BCR?

    <p>The antigen-BCR complex is internalized and processed via MHC Class II</p> Signup and view all the answers

    list the pashes of adaptive immunity?

    <p>antigen recognition lymphocytes activation antigen elimination contraction (homeostasis) memory.</p> Signup and view all the answers

    what are naive lymphocytes?

    <p>mature T or B cells never encountered foreign antigen.</p> Signup and view all the answers

    what would the binding of T and B cells to antigens lead to?

    <p>activation, proliferation , and differentiation of T and B cells.</p> Signup and view all the answers

    what is the function of B cells?

    <p>production of antibodies, (soluble immunity).</p> Signup and view all the answers

    what is the function of helper T cells?

    <p>interaction with other immune cells to coordinate an effective immune response.</p> Signup and view all the answers

    what's the function of Cytotoxic T cells?

    <p>kill infected or malignant host cells.</p> Signup and view all the answers

    what type of immunity block infections and eliminate extracellular microbes?

    <p>Humoral (soluble) immunity carried by B cells through the production of antibodies.</p> Signup and view all the answers

    what r the immune cells that activate phagocytosis to kill microbes?

    <p>helper T cells (cell-mediated immunity).</p> Signup and view all the answers

    what type of immune cells involved in killing infected cells and eliminate reservoirs of infection?

    <p>Cytotoxic T cells.</p> Signup and view all the answers

    what's the function of memory cells?

    <p>prevent future infection or lessen the severity of the disease ( remain to respond faster).</p> Signup and view all the answers

    what does TCR and BCR stand for?

    <p>T-cell receptor B-cell receptor</p> Signup and view all the answers

    what type of receptor has alpha and beta chain?

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

    what type of receptor has light and heave chain?

    <p>BCR/surface immunoglobin.</p> Signup and view all the answers

    what type of receptor involved in a direct recognition of an antigen?

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

    describe 2 ways that TCR can recognise antigen (foreign proteins)?

    <p>1- MHC class I pathway: from intracellular pathogens where foreign protein is made( by host cell)</p> <p>2- MHC class II pathway : from extracellular pathogens.</p> Signup and view all the answers

    what's MHC?

    <p>( major histocompatibility complex) and is a self molecule that TCR bind to to recognise antigens,</p> <p>in human its called HLA</p> Signup and view all the answers

    which acts as a co-receptor for MHC class I?

    <p>CD8</p> Signup and view all the answers

    which acts as a co-receptor for MHC class II?

    <p>CD4</p> Signup and view all the answers

    what's the outcome of MHC class I pathway?

    <p>death of presenting cell by cytotoxic T cells.</p> Signup and view all the answers

    what's the outcome of the MHC class II pathway?

    <p>activation of helper T cell.</p> Signup and view all the answers

    in which pathway does the digestion of protein in proteasomes occur?

    <p>MHC class I pathway as protein made in the cell.</p> Signup and view all the answers

    in which pathway does the endocytosis of (extracellular) protein/pathogen occur?

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

    list the 3 classical MHC class I genes in humans?

    <p>HLA-A HLA-B HLA-C</p> Signup and view all the answers

    list the main MHC class II genes in humans?

    <p>1- HLA-DPA1 2- HLA-DPB1 3- HLA-DQA1 4-HLA-DQB1 5- HLA-DRA 6-HLA-DRB1</p> Signup and view all the answers

    MHC class II is expressed by?

    <p>antigen-presenting cells (eg, dendritic cells, macrophages, B cells).</p> Signup and view all the answers

    what cells r considered as ( professional antigen presenting cell)?

    <p>DCs (dendritic cells).</p> Signup and view all the answers

    describe the role of DCs as an antigen presenting cell?

    <p>1- bacter engulfed by phagocytosis into a dc&gt; phagosome</p> <p>2- lysosomes fuse w phago and digest the bacter</p> <p>3- immunodominant epitopes-MHC II presented on the cell surface.</p> Signup and view all the answers

    which part of the TCR structure interacts with the antigen?

    <p>the variable (V) domain on both alpha and beta chain.</p> Signup and view all the answers

    what generates the variable domains of BCR and TCR?

    <p>recombination of gene segments.</p> Signup and view all the answers

    where does the negative selection (t-cells) occur?

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

    what type of cells undergo receptor editing/apoptosis in bone marrow?

    <p>B cells.</p> Signup and view all the answers

    what receptors involved in the co-stimulatory signal in T-cell activation?

    <p>CD28 on T cell binds to B7 on APC.</p> Signup and view all the answers

    briefly label the three signals of T cell activation?

    <p>1- Ag recognition</p> <p>2- co-stimulation</p> <p>3-cytokines signalling</p> Signup and view all the answers

    label the B cell activation signals

    <p>1- antibody-ag recognition</p> <p>2- co-stimulation from helper T-cells</p> <p>3- cytokines</p> Signup and view all the answers

    what receptors involved in B&T cells interaction/co-stimulation?

    <p>CD40L on the h T-cell CD40 on the B cell</p> Signup and view all the answers

    site of immune cells generation?

    <p>in primary generative lymphoid tissue -bone marrow -thymus</p> Signup and view all the answers

    site of lymphocytes interaction w ag?

    <p>in secondary (peripheral) lymphoid tisse/ lymph nodes:</p> <ul> <li>spleen</li> <li>MALT (mucosal associated lymphoid tissue).</li> </ul> Signup and view all the answers

    where does antigen in blood go to?

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

    where does antigen in tissue/periphery go to?

    <p>to lymph node through lymphatics by APCs.</p> Signup and view all the answers

    what's the collection of T and B cells in the node where formation of mature,effector T&B cells occur?

    <p>lymphoid follicles.</p> Signup and view all the answers

    encapsulated highly vascular organ that filters blood, eliminate pathogens, also has follicles for B-T maturation/activation?

    <p>Spleen.</p> Signup and view all the answers

    what's the first antibody produced?

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

    which antibody involved in Opsonisation?

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

    what receptors triggers/activate phagocytosis ?

    <p>FC receptors</p> Signup and view all the answers

    what receptor does NK cell express? ( that allows recog and killing of antibody-coated cell).

    <p>fC(CD16).</p> Signup and view all the answers

    what cells inhibit immune response? (important in self-tolerance).

    <p>(Treg cells) inc production of IL-10, TGF-B</p> Signup and view all the answers

    Study Notes

    Adaptive Immunology

    • Adaptive immunity is a feature of the immune system involving antigen presentation, lymphocyte activation, B cell effector function, T cell effector function, and memory.
    • A microbe is initially encountered by the innate immune system (hours).
    • B and T lymphocytes (days) specifically recognize and target a pathogen, producing an antibody response.
    • Antigen is any molecule recognized specifically by lymphocytes or antibodies.
    • Naive lymphocytes: mature T or B cells never encountering foreign antigen.
    • T and B cells bind to specific antigens. This leads to their activation, proliferation, and differentiation.
    • Adaptive immunity is mediated by T and B cells.

    Phases of Adaptive Immunity

    • Antigen recognition, lymphocyte activation, antigen elimination, contraction (homeostasis), and memory phases.
    • Antigen recognition is followed by differentiation causing clonal expansion of naive T cells and naive B cells.
    • Antibody-producing cells and effector T cells eliminate the antigen,
    • The immune response contracts (homeostasis)
    • Memory cells remain to aid future immune response

    Functions of Adaptive Immunity

    • B cells: mediate humoral (soluble) immunity by producing antibodies.
    • Helper T cells: interact with other immune cells to direct an effective response.
    • Cytotoxic T cells: kill infected or malignant host cells.

    Memory in the Adaptive Immune System

    • After infection resolution, memory cells remain.
    • These aid in faster response during future infection and lessen the disease severity.
    • Secondary response is much faster and involves less antigen than a primary response.

    TCR and BCR

    • TCR (T-cell receptor): antigen-binding site, variable regions, constant regions, transmembrane regions, alpha and beta chains.
    • BCR (B-cell receptor): antigen-binding site, light chain, heavy chain, transmembrane region.
    • BCR directly recognizes antigen.
    • TCR does not directly recognize antigen, instead proteins must be processed into peptides and presented in MHC for T cell recognition.

    Antigen Presentation

    • T cells cannot directly recognize foreign proteins.
    • Proteins must be processed into peptides and presented with major histocompatibility complex (MHC) molecules.
    • MHC class I pathway occurs in intracellular pathogens where the foreign protein is made inside the host cell.
    • MHC class II pathway occurs in extracellular pathogens where the foreign protein is taken up.

    MHC Class I Pathway

    • Foreign proteins made inside the presenting cell are presented on MHC class I molecules.
    • These molecules are recognized by cytotoxic T cells which have the CD8 marker acting as a coreceptor.
    • This leads to death of the presenting cell.

    MHC Class II Pathway

    • Foreign proteins taken up by the presenting cell are presented on MHC class II molecules.
    • These molecules are recognized by helper T cells which have the CD4 marker acting as a coreceptor.
    • This leads to activation of the helper T cell.

    Dendritic Cells

    • Play a central role in processing and presenting antigen.
    • They're professional antigen-presenting cells (APCs), along with macrophages and B cells.

    Diversity of TCR and BCR

    • The variable domains are generated via recombination of gene segments.
    • This high diversity allows for a large number of different receptors from a limited number of gene segments.

    Negative Selection

    • Random generation of BCRs/TCRs can result in recognition of self-antigens.
    • Immature T cells recognising MHC molecules with self-peptides undergo apoptosis.
    • In the bone marrow, B cells may undergo receptor editing or apoptosis.

    Activation of Adaptive Cells

    • T Helper cell activation: three signals needed (TCR - antigen recognition, co-stimulation by presenting cell, and cytokines). This leads to clonal expansion and differentiation.
    • B cell activation: Requires three signals: BCR (antigen recognition), co-stimulation from Helper T cell, and cytokines.

    B Cell-T Cell Interactions

    • Co-stimulation results from CD40L on activated Helper T cell and CD40 on the B cell.
    • Cytokines influence the antibody type produced.

    Lymphocyte Trafficking

    • Antigens from the tissue are delivered to the lymph nodes via lymphatics.
    • Antigens in the blood are delivered to the spleen. Lymphoid tissue is where immune cells are generated and mature, includes bone marrow and thymus, as well as secondary locations like lymph nodes and spleen for antigen interaction.

    Lymph Node

    • Encapsulated organs throughout the body, transporting antigens from periphery through lymph.
    • Antigen presenting cells deliver antigens to lymphoid follicles containing T & B cells.
    • Proliferation leads to germinal center formation and maturation to effector T & B cells.

    The Spleen

    • Filters blood, eliminating blood-borne pathogens.
    • Lymphocyte follicles generate germinal centers for antigen activation, leading to effector T & B cell generation.

    Effector Functions of Adaptive Lymphocytes

    • B cell function: Antigen recognition leads to plasma cells producing antibodies targeting the microbe. Antibody function involves neutralization, phagocytosis, and complement activation.

    Antibody Isotypes

    • There are five different antibody classes/isotypes (IgG, IgA, IgE, IgM, IgD).
    • Differences in constant regions lead to different biological functions like complement fixation.
    • IgM is the first antibody produced.

    Antibody Isotype Switching

    • Depending on the signal, B cells can switch from producing IgM to other isotypes such as IgG, IgE, or IgA.
    • The switch depends on cytokine and receptor interactions with Helper T cells.

    Antibody Isotype Differences

    • Distinct functions (e.g., protection, allergies, etc.)
    • Vary in locations in the body (plasma, secretions, mucosa etc.)
    • Different molecular forms (monomer, dimer, pentamer, etc.).

    Role of Antibodies

    • Antibodies aid in microbe neutralization, phagocytosis, complement activation and cytotoxicity in innate immune cells, and other immune system processes.

    Antibodies: Neutralisation

    • Antibodies block microbe entry, preventing infection.
    • They block toxins from binding to their target, neutralizing their effects.

    Antibodies: Opsonization

    • Antibody binding to microbes enhances phagocytosis by phagocytes.

    Antibodies: ADCC

    • Antibodies coating a cell target NK cells which then kill the antibody-coated cells.

    T cell Function

    • Helper T cells (CD4+): Activation, proliferation, differentiation of T and B cells.
    • Cytotoxic T cells (CD8+): Killing of infected cells.

    Cytotoxic T Cells

    • These cells kill infected host cells.
    • Their mechanism of cytotoxicity is similar to NK cells.

    T Helper Cells

    • Different types of T helper cells exist, depending on the environment and cytokines present.
    • Treg cells (regulatory T cells) regulate the immune response and are important for maintaining self-tolerance.

    T Helper Cell Subsets

    • Different T helper subtypes (Th1, Th2, Th17) have specific cytokine profiles and target different cells (e.g., macrophages, eosinophils, neutrophils).

    Memory

    • Most lymphocytes die after an immune response, however memory cells persist.
    • Memory cells reactivate much faster than naive T or B cells.
    • Secondary response involves significantly less antigen and is much faster than primary response.

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    Adaptive Immunology PDF

    Description

    Test your knowledge on adaptive immunity and its mechanisms in the immune system. This quiz covers concepts like antigen presentation, lymphocyte activation, and the phases of adaptive immunity. Challenge yourself to understand how B and T cells contribute to a specific immune response.

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