Immunology Quiz on Antigens
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Questions and Answers

What are epitopes?

  • Parts of an antigen recognized by immune cells (correct)
  • Components that trigger a fever response
  • Molecules that prevent disease transmission
  • Proteins that bind to antibodies

    • Which type of antigen is considered incomplete?

  • Polysaccharides from bacteria
  • Lipopolysaccharides
  • Haptens (correct)
  • Complete antigens like hemagglutinin

    • What is an example of a lipid antigen?

  • Lipopolysaccharide (LPS) (correct)
  • Hemagglutinin
  • Capsule polysaccharides
  • Penicillin

    • Which of the following is NOT a complete antigen?

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

    What element increases the immunogenicity of influenza virions?

    <p>Proteins like hemagglutinin (B)</p> Signup and view all the answers

    What is the primary function of the antigen-binding sites on an antibody?

    <p>To specifically recognize an epitope (C)</p> Signup and view all the answers

    Which statement accurately describes a given B cell's ability to recognize epitopes?

    <p>It can only produce antibodies for one specific epitope. (A)</p> Signup and view all the answers

    Which antibody isotype is most likely to predominate in mucosal areas?

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

    What differentiates the five antibody isotypes?

    <p>The constant region of the heavy chain (C)</p> Signup and view all the answers

    How does isotype switching occur in B cells?

    <p>By changing the class of antibody made (B)</p> Signup and view all the answers

    What role do MHCs play in tissue transplants?

    <p>They are the primary proteins for matching between donor and recipient. (B)</p> Signup and view all the answers

    What is the process called that lymphocytes use to differentiate self from foreign MHCs?

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

    What must happen for T cells to become activated?

    <p>They must interact with antigen-presenting cells. (C)</p> Signup and view all the answers

    How do T cytotoxic cells recognize antigens?

    <p>By interacting with MHC I-antigen complexes. (A)</p> Signup and view all the answers

    Which T cell type interacts with antigens presented by MHC II molecules?

    <p>T helper cells (B)</p> Signup and view all the answers

    What happens if MHCs are not closely matched in a transplant?

    <p>The transplanted tissue may be recognized as foreign. (A)</p> Signup and view all the answers

    What is the role of antigen-presenting cells (APCs) in the immune response?

    <p>They present antigens to T cells for activation. (D)</p> Signup and view all the answers

    What must APCs do after bearing MHC-antigen complexes?

    <p>Migrate to lymphoid tissues for interaction. (D)</p> Signup and view all the answers

    What are the two main branches of adaptive immunity?

    <p>Humoral and Cellular (B)</p> Signup and view all the answers

    Which of the following correctly describes a T helper cell?

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

    What is the primary difference between T and B cells?

    <p>B cells produce antibodies; T cells do not. (B)</p> Signup and view all the answers

    What is immunogenicity?

    <p>The capacity of an antigen to provoke an immune response. (B)</p> Signup and view all the answers

    How do T and B cell receptors contribute to antigen recognition?

    <p>B cell receptors bind to soluble antigens while T cell receptors recognize processed antigens presented by MHC. (A)</p> Signup and view all the answers

    What is self-tolerance in the immune system?

    <p>The state in which the body does not mount an immune response against its own tissues. (C)</p> Signup and view all the answers

    What is the role of haptens in immunology?

    <p>They bind to proteins to form complete antigens. (D)</p> Signup and view all the answers

    Which of the following describes a characteristic of innate immunity?

    <p>It includes physical barriers like skin and mucous membranes. (C)</p> Signup and view all the answers

    What is the primary source of antibodies in artificially acquired passive immunity?

    <p>Animal sources such as horses and rabbits (D)</p> Signup and view all the answers

    What does antiserum specifically target?

    <p>Specific toxins or venoms (C)</p> Signup and view all the answers

    Which statement is true about the protection provided by artificially acquired passive immunity?

    <p>It offers temporary protection. (D)</p> Signup and view all the answers

    Which type of immune response is activated when an invader is detected by third-line defenses?

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

    What are cytokines primarily responsible for in the immune response?

    <p>Stimulating inflammation and recruiting leukocytes (A)</p> Signup and view all the answers

    Which defenses are involved in the first line of immune defense?

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

    What happens after an invader overcomes first- and second-line defenses?

    <p>The body activates its adaptive defenses. (D)</p> Signup and view all the answers

    Which of the following describes what second-line defenses include?

    <p>Cellular responses such as inflammation (B)</p> Signup and view all the answers

    What effect do cytokines have on fever during the immune response?

    <p>They promote an increase in body temperature. (D)</p> Signup and view all the answers

    What type of defenses are categorized under 'Innate immunity'?

    <p>Barrier and chemical defenses (D)</p> Signup and view all the answers

    What initial symptoms did Hassan exhibit that led to his parents' assumption of overexertion?

    <p>Tiredness and leg pains (B)</p> Signup and view all the answers

    What was the pediatrician's immediate response to Hassan's worsening symptoms during the second visit?

    <p>To order blood tests (B)</p> Signup and view all the answers

    Which of the following is a common characteristic of acute lymphoblastic leukemia (ALL) as explained by the oncologist?

    <p>Overproduction of abnormal lymphocytes (B)</p> Signup and view all the answers

    What condition might lead to increased fatigue and anemia in patients with acute lymphoblastic leukemia?

    <p>Low red blood cell count (B)</p> Signup and view all the answers

    What diagnostic tests were ordered to assess Hassan's health condition?

    <p>Complete blood count and serum chemistry tests (C)</p> Signup and view all the answers

    What was the primary concern that led to the referral to a pediatric oncologist?

    <p>Abnormal blood test results suggesting leukemia (A)</p> Signup and view all the answers

    How did the oncologist describe the behavior of the abnormal lymphocytes in patients with ALL?

    <p>They compress healthy cells in the bone marrow. (B)</p> Signup and view all the answers

    What symptom prompted Hassan's mother to take him back to the pediatrician a second time?

    <p>Increased leg pain and fever (B)</p> Signup and view all the answers

    Flashcards

    Antigenic epitopes

    Parts of an antigen recognized by B and T cells.

    Antigens

    Substances that trigger an immune response.

    Complete antigens

    Substances that have both immunogenicity and reactivity.

    Haptens

    Small molecules that are not immunogenic by themselves.

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    Immunogenicity

    Ability to stimulate an immune response.

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    Adaptive Immunity

    The body's third line of defense against pathogens, characterized by specificity and memory.

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    Innate Immunity

    The body's first and second lines of defense, acting quickly and generally.

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    T cells and B cells

    Two key cell types of the adaptive immune response with distinct roles.

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    T helper cells

    Cells that help activate other immune cells in the adaptive response.

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    T cytotoxic cells

    Cells that directly kill infected or cancerous cells.

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    Self-tolerance

    The ability of the immune system to recognize and not attack the body's own cells.

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    T cell receptors

    Molecules on T cells that recognize specific antigens.

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    Antigen-binding site

    The specific region on an antibody molecule that recognizes and binds to a particular epitope on an antigen.

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    Epitope

    The specific part of an antigen that an antibody recognizes and binds to.

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    Antibody variable region

    The region of an antibody that is responsible for recognizing and binding to a specific epitope.

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    Antibody constant region

    The region of an antibody that is responsible for mediating effector functions, such as activating complement or binding to cells.

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    Isotype switching

    A process by which a B cell can change the class of antibody it produces without altering the specific epitope it recognizes.

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    MHCs in Transplants

    Major Histocompatibility Complex (MHC) proteins must match between a tissue donor and recipient to prevent the recipient's immune system from rejecting the transplant.

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    Allorecognition

    The process by which lymphocytes differentiate between self and foreign MHCs, particularly important in tissue transplantation.

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    What happens when MHCs don't match?

    If MHCs don't match in a tissue transplant, the recipient's immune system will recognize the transplanted tissue as foreign and attack it, potentially leading to rejection.

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    APC's role in T cell activation

    Antigen Presenting Cells (APCs) process antigens and display them on their MHC molecules, enabling them to activate T cells.

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    MHC I and T cytotoxic cell interaction

    T cytotoxic cells (Tc) interact with antigens presented on MHC I molecules by APCs. This leads to the destruction of infected or cancerous cells.

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    MHC II and T helper cell interaction

    T helper cells (Th) recognize and bind to antigens presented on MHC II molecules by APCs. This interaction is essential for activating immune responses.

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    Why is finding a match difficult?

    Finding a tissue transplant match with compatible MHCs can be challenging because individuals have unique MHC profiles, making it hard to find a close enough match.

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    What happens in Stage 2 of T cell activation?

    In Stage 2, APCs carrying processed antigens migrate to lymph nodes and interact with T cells. T cells with compatible receptors bind to the displayed antigens, leading to activation.

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    Hassan's initial symptoms

    Hassan, a middle schooler, complained of feeling tired and having leg pain. His dad initially attributed these symptoms to overexertion at soccer practice.

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    Hassan's worsening symptoms

    Weeks later, Hassan developed a fever, shortness of breath, and worsening leg pain.

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    Urgent care visit

    Hassan's mom took him to the local urgent care center where he was treated for what was believed to be a bacterial infection.

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    Pediatrician follow-up

    The urgent care doctor advised Hassan's mom to follow up with his pediatrician if his symptoms worsened or new symptoms developed.

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    Hassan's continued symptoms

    Despite antibiotics, Hassan's leg pain worsened, he became fatigued, and developed a recurring fever.

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    Pediatrician's additional testing

    Due to Hassan's persistent bone pain and an enlarged spleen, the pediatrician ordered a comprehensive blood test panel.

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    Acute lymphoblastic leukemia (ALL)

    Hassan's blood test results revealed the presence of acute lymphoblastic leukemia, a type of blood cancer.

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    ALL symptoms

    ALL patients have increased abnormal lymphocytes in their blood, which crowd out healthy cells in the bone marrow, causing pain, fatigue, and anemia.

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    Artificial Passive Immunity

    A type of immunity where a patient receives protective antibodies from a medical treatment, often from animals like horses, rabbits, or goats. This provides temporary protection and may trigger an immune response in the patient.

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    Antiserum

    A preparation of antibodies developed to neutralize specific toxins or venoms. It is a key component of artificial passive immunity.

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    First-Line Defenses

    The initial barriers that protect the body from pathogens, including mechanical barriers like skin and mucous membranes, and chemical barriers like sweat and saliva.

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    Second-Line Defenses

    The body's internal defenses that act quickly and generally to fight off infections. These include cellular and molecular defenses, inflammation, and fever.

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    Molecular Defenses

    Part of the second-line immune response, these involve molecules like cytokines that help regulate inflammation and recruit immune cells.

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    Inflammation

    A localized response to tissue injury or infection, characterized by redness, swelling, heat, and pain.

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    VASCULAR CHANGES

    One of the key processes that occur during inflammation. These changes involve dilation of blood vessels to increase blood flow to the area of infection.

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    LEUKOCYTE RECRUITMENT

    Another key part of inflammation where immune cells (leukocytes) are called in to fight the invaders.

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    RESOLUTION

    The final stage of inflammation where the damaged tissue is repaired and the infection is cleared.

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    Study Notes

    Microbiology: Basic and Clinical Principles - Chapter 12

    • Adaptive immunity is the body's third and final line of defense
    • It engages when innate first- and second-line defenses fail
    • It is a set of acquired defenses, responding to specific antigens and establishing immunological memory

    Adaptive Immunity Differences from Innate Immunity

    • Adaptive immunity takes longer to mount a response (days to weeks)
    • Primary exposure response is slow
    • It is specific to particular antigens
    • Adaptive immunity has immunological memory where secondary exposure to antigens is rapid and effective

    Adaptive Immune System Structure

    • Subdivided into two highly-dependent branches:
      • Cellular response (T cell-mediated immunity)
      • Humoral response (antibody-mediated immunity)
    • Both branches aim to eliminate the antigen and remember it for quicker responses in the future

    Adaptive Immune Response Stages

    • Stage 1: Antigen Presentation

      • Dendritic cells and other antigen-presenting cells (APCs) process antigens
      • APCs present antigens to T cells
      • B cells can directly interact with antigens without APCs

    • Stage 2: Lymphocyte Activation

      • Lymphocytes are activated by cytokines (signaling molecules) after successful antigen presentation
      • Activated T cells influence B cell activation

    • Stage 3: Lymphocyte Proliferation and Differentiation

      • Activated B and T cells undergo multiple rounds of cell division, called clonal expansion
      • Some cells differentiate into effector cells which actively fight the antigen, while others become memory cells to quickly respond in future encounters

    • Stage 4: Antigen Elimination and Memory

      • Cellular and humoral responses collaborate to eliminate the antigen
      • Effector cells die off after the threat is eliminated
      • Memory cells remain in lymphatic tissues for rapid response to future encounters with the same antigen

    T Cells and B Cells

    • T cells and B cells are crucial adaptive immunity leukocytes (lymphocytes)
    • T cells originate in the bone marrow and mature in the thymus
    • B cells originate and mature in the bone marrow
    • Mature B and T cells reside primarily in lymphoid tissues at low levels in circulation

    T Cells and B Cells Structure

    • T cells and B cells have thousands of receptors on their surfaces; each recognizes a specific epitope
    • These receptors are "monospecific"-that is, they only recognize a specific epitope but the body makes diverse types of receptors

    T Cells and B Cells Functions

    • T cells have roles in both humoral and cellular branches
    • B cells coordinate the humoral response by making antibodies
    • Our immune system generates a wide array of both T and B cells with the capacity to recognize almost any antigen

    Immunogenicity

    • Antigens are any substance triggering an immune response if presented in the correct context

    • Mostly proteins or polysaccharides

      • Proteins are predominantly produced by virus, bacteria, and fungus -Also abnormal proteins produced by cancer cells that may also be antigens

    • Cancer cells also frequently produce proteins, and/or polysaccharides

    • Immunogenicity is affected by size, complexity, and composition

      • Proteins are usually more immunogenic than lipids and polysaccharides

    • Haptens are incomplete antigens, needing linkage to a complex protein or polysaccharide to trigger an immune response

    Antigen Features

    • Epitopes are parts of an antigen that B and T cells recognize
    • T cell receptors (TCRs) are involved in antigen recognition by T cells
    • B cell receptors (BCRs) are associated with antigen recognition by B cells

    T Cell Subclasses

    • Helper T cells (TH cells): Most numerous type, releasing cytokines stimulating and coordinating immune responses

    • Cytotoxic T cells (Tc): Directly destroying infected, damaged, foreign, or cancerous cells

    • Regulatory T cells (Treg): Controlling the function of other immune cells

    T Helper 1 (TH1) cells:

    • Support the cellular response by activating T cytotoxic cells, macrophages, and natural killer cells primarily engaging with intracellular pathogens

    T Helper 2 (TH2) cells:

    • Support the humoral response by activating B cells to produce antibodies promoting the elimination of extracellular pathogens

    Regulatory T cells (Treg):

    • Control the functions of other immune cells, maintaining immune tolerance

    MHCs and Tolerance

    • MHC proteins serve as "self-proteins" or human leukocyte antigens (HLAs)
    • T cells screened in the thymus ensuring they correctly recognize "self" MHC molecules and do not attack "self" cells
    • B cells screened in bone marrow, ensuring antibodies do not attack "self" antigens

    T Cells and B Cells Activation

    • T-cells require two signals for activation

      • A primary signal based on MHC-antigen interaction with the T-cell receptor (TCR)
      • A secondary signal based on co-stimulatory proteins interactions

    • T-independent antigens trigger B cell activation via direct binding to multiple BCRs on the same B-cell, stimulating its proliferation and differentiation into plasma cells and memory cells

    Superantigens

    • Superantigens are exceptionally potent T helper cell activators
    • Directly crosslink MHC II with the T helper cell TCR
    • Triggering a massive, non-specific stimulation of T cells and a release of cytokines, causing potential shock in the body

    Effector and Memory T Cells

    • Effector T cells eliminate antigens when the threat subsides (die off)
    • Memory T cells, long-lived, remain in lymphatic tissues, enabling a swift response to subsequent exposures

    MHC I

    • All nucleated body cells have MHC I
    • Display intracellular antigens to cytotoxic T cells

    MHC II

    • Only antigen-presenting cells (APCs) have MHC II
    • Display extracellular antigens to helper T cells

    Humoral Immunity

    • Involves B cells producing antibodies

      • T dependent activation via multiple signals for B cells
      • T independent activation via direct multiple BCR binding to antigens

    • The antigen binding region is termed variable

    • Isotype Switching: altering the class of antibody produced by the plasma cell but not changing the antigen the antibody recognizes

      • 5 antibody isotypes: IgG, IgA, IgM, IgE, IgD

      • Each antibody isotype has specific specializations and predominates in different areas of the body (e.g., blood, secretions, mucosal membranes)

    Antibody Structure

    • Antibodies ('immunoglobulins') have a monomeric structure with two heavy and two light chains held together by disulfide bonds to form a 'Y' shape.

    • Antigen-binding sites - Located on varying regions - are for precise antigen recognition

    Antibody Function

    • Antibodies neutralize pathogens (block toxins)
    • Activate complement (cytolysis, inflammation, opsonization)
    • Increase phagocytosis (via precipitation, agglutination, opsonization)

    Immunological Memory

    • Created when memory cells are created - and are responsible for fast and amplified response to future encounters

    • Important for generating quick high antibody titers to specific antigens.

    • Serological testing measure antibody titers (antibody levels in the blood) to determine exposure history (disease, vaccine).

    Four Classes of Adaptive Immunity

    • Naturally acquired active immunity: Results from contracting an infection
    • Artificially acquired active immunity: Results from vaccinations
    • Naturally acquired passive immunity: Antibodies pass from mother to offspring (e.g., across placenta)
    • Artificially acquired passive immunity: Antibodies are administered as a treatment (e.g., antiserum)

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    Microbiology: Basic and Clinical Principles Chapter 12 - Adaptive Immunity PDF

    Description

    Test your knowledge on antigens and their characteristics in this immunology quiz. Explore concepts like epitopes, incomplete antigens, and the factors influencing immunogenicity. Challenge yourself with specific examples and key definitions.

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