lecture-32-immune hypersensitivity- kaushik
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Questions and Answers

What is the role of IgM antibodies in transfusion reactions compared to IgG antibodies?

  • IgM antibodies do not participate in hemolytic reactions.
  • IgM antibodies solely target viral infections.
  • IgM antibodies are less effective at complement activation.
  • IgM antibodies are more effective at complement activation. (correct)
  • Which symptom is commonly associated with hemolytic disease of the newborn?

  • Excessive leukocyte production
  • Severe jaundice (correct)
  • Increased platelet count
  • High hemoglobin levels
  • What is the purpose of administering Rhogam during pregnancy?

  • To enhance fetal blood count.
  • To increase maternal IgG production.
  • To prevent hemolytic disease in a subsequent pregnancy. (correct)
  • To stimulate fetal growth.
  • What can trigger drug-induced hemolytic anemia?

    <p>Adverse reactions to non-specific adsorbed drugs on RBC membranes. (A)</p> Signup and view all the answers

    In thrombocytopenia, what is a prominent clinical feature observed?

    <p>Purpura, areas of purplish discoloration. (A)</p> Signup and view all the answers

    What are isohemagglutinins?

    <p>Antibodies produced in response to non-self blood group antigens (B)</p> Signup and view all the answers

    What primarily causes immediate hemolytic transfusion reactions?

    <p>ABO blood-group incompatibilities (A)</p> Signup and view all the answers

    What are the symptoms of immediate hemolytic transfusion reactions?

    <p>Hemoglobinuria, fever, and chills (B)</p> Signup and view all the answers

    Delayed hemolytic transfusion reactions are typically caused by which type of antibodies?

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

    How long after a transfusion do delayed hemolytic transfusion reactions usually develop?

    <p>2-6 days (D)</p> Signup and view all the answers

    What is a primary treatment for immediate hemolytic transfusion reactions?

    <p>Prompt termination of the transfusion (B)</p> Signup and view all the answers

    What role does H antigen play with ABO/ABH blood-group antigens?

    <p>It is present in all blood types (B)</p> Signup and view all the answers

    Which mechanism is involved in the destruction of transfused RBCs during a transfusion reaction?

    <p>Complement-mediated lysis (B)</p> Signup and view all the answers

    Which of the following conditions is a potential cause of drug-induced hemolytic anemia?

    <p>Autoimmune response to medications (C)</p> Signup and view all the answers

    To prevent erythroblastosis fetalis, which intervention is critical?

    <p>Administering Rh immunoglobulin to Rh-negative mothers (A)</p> Signup and view all the answers

    What antibody is primarily responsible for mediating immediate hemolytic transfusion reactions?

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

    Which blood group antigen is present in all blood types?

    <p>H antigen (C)</p> Signup and view all the answers

    What is a common clinical manifestation associated with immediate hemolytic transfusion reactions?

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

    Delayed hemolytic transfusion reactions are primarily associated with which class of antibodies?

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

    Which of the following treatments is critical for managing immediate hemolytic transfusion reactions?

    <p>Termination of transfusion and diuretic administration (C)</p> Signup and view all the answers

    What is the primary cause of Goodpasture's syndrome?

    <p>Autoantibodies against collagen proteins (A)</p> Signup and view all the answers

    Which statement best describes pemphigus?

    <p>It leads to the formation of blisters due to autoantibodies against desmogleins. (A)</p> Signup and view all the answers

    What triggers type II hypersensitivity in organ transplantation?

    <p>Pre-existing alloantibodies against MHC molecules (B)</p> Signup and view all the answers

    In type III hypersensitivity, what is the primary consequence of immune complex deposition?

    <p>Recruitment of neutrophils and tissue damage (D)</p> Signup and view all the answers

    What standard treatment is typically administered for pemphigus?

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

    What primarily causes mild to severe anemia in the fetus during erythroblastosis fetalis?

    <p>Destruction of fetal blood cells by maternal antibodies (C)</p> Signup and view all the answers

    Which of the following is a common result of IgG-mediated transfusion reactions?

    <p>Extravascular destruction of RBCs (B)</p> Signup and view all the answers

    How can the risk of thrombocytopenia be increased through hypersensitivity reactions?

    <p>By contributing to increased platelet destruction via anti-platelet antibodies (D)</p> Signup and view all the answers

    What clinical manifestation characterizes the condition of thrombocytopenia?

    <p>Purplish discoloration of the skin known as purpura (A)</p> Signup and view all the answers

    Which condition is most likely to occur if maternal IgG antibodies target fetal blood group antigens?

    <p>Hemolytic disease of the newborn (A)</p> Signup and view all the answers

    What primarily distinguishes autoimmune hemolytic anemia from hemolytic anemia caused by alloantibodies?

    <p>Autoimmune hemolytic anemia involves antibodies directed against one's own red blood cells. (C)</p> Signup and view all the answers

    Which mechanism does not contribute to the destruction of cells in type II hypersensitivity?

    <p>Direct lysis by IgE antibodies. (C)</p> Signup and view all the answers

    What is a characteristic feature of cold autoantibodies in autoimmune hemolytic anemia?

    <p>They may trigger episodes of acute hemolysis during colder months. (C)</p> Signup and view all the answers

    Which of the following is an example of a reaction that can induce type II hypersensitivity?

    <p>Blood transfusion reactions. (D)</p> Signup and view all the answers

    What is the most common response of the body during type II hypersensitivity when autoantibodies are produced?

    <p>Direct binding of antibodies to self-antigens leading to cell lysis. (C)</p> Signup and view all the answers

    What is a significant outcome of the conversion of hemoglobin to bilirubin in cases of erythroblastosis fetalis?

    <p>Brain damage due to bilirubin deposition (C)</p> Signup and view all the answers

    In drug-induced hemolytic anemia, how do certain drugs contribute to the production of antibodies against RBCs?

    <p>By adsorbing non-specifically to RBC membrane proteins (B)</p> Signup and view all the answers

    What is the primary mechanism that leads to thrombocytopenia mediated by type II hypersensitivity?

    <p>Destruction of platelets by antiplatelet antibodies (A)</p> Signup and view all the answers

    Which of the following conditions can lead to severe consequences in newborns due to maternal IgG antibody transfer?

    <p>Hemolytic disease of the newborn (A)</p> Signup and view all the answers

    What prompts the administration of Rhogam to Rh-negative mothers during pregnancy?

    <p>To inhibit the formation of maternal IgG antibodies against fetal Rh+ cells (D)</p> Signup and view all the answers

    What is the primary cause of a transfusion reaction when a type ‘A’ individual receives type ‘B’ blood?

    <p>Binding of anti-B isohemagglutinins to B blood cells (C)</p> Signup and view all the answers

    Which statement describes the characteristic of isohemagglutinins in adults?

    <p>They are predominantly of IgM isotype for antigens not expressed (A)</p> Signup and view all the answers

    What is a potential complication of hemoglobin accumulation in the kidneys post-transfusion?

    <p>Tubular necrosis due to toxicity (C)</p> Signup and view all the answers

    How does the presence of the H antigen influence blood transfusions?

    <p>It serves as the only blood group antigen recognized in all individuals (D)</p> Signup and view all the answers

    What is the role of natural exposure to microbial antigens in blood type antibody production?

    <p>It stimulates antibody production specific to non-self blood group antigens (B)</p> Signup and view all the answers

    Flashcards

    Hemolytic disease of the newborn

    A condition where maternal antibodies attack fetal blood cells, leading to anemia and potentially severe consequences.

    Erythroblastosis fetalis

    Severe form of hemolytic disease of the newborn; caused by maternal IgG attacking fetal blood cells.

    Drug-induced hemolytic anemia

    A condition where certain drugs induce the body to produce antibodies that attack red blood cells, causing anemia.

    Type II hypersensitivity

    Immune reaction where antibodies bind to antigens on cell surfaces, triggering complement activation and cell destruction.

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    Thrombocytopenia

    Low platelet count, leading to abnormal bleeding.

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    ABO blood group

    A blood group system based on the presence or absence of A and B antigens on red blood cells, determining blood types A, B, AB, and O.

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    Isohemagglutinins

    Antibodies (usually IgM) against ABO blood group antigens that are naturally present in the blood of individuals lacking those antigens.

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    H antigen

    A carbohydrate antigen present on all blood types, serving as a precursor for A and B antigens.

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    Transfusion reaction

    An adverse immune response that occurs when incompatible blood types are mixed, leading to destruction of transfused red blood cells.

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    Complement-mediated lysis

    A process where the complement system, a part of the immune system, destroys cells by forming pores in their membranes.

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    Hemoglobinuria

    Presence of hemoglobin in the urine, resulting from the breakdown of red blood cells.

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    Bilirubin buildup

    An increase in bilirubin levels in the blood, caused by the breakdown of heme from red blood cells.

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    Rh factor

    An antigen found on red blood cells, categorized as Rh-positive or Rh-negative.

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    Delayed hemolytic transfusion reaction

    A delayed immune response to transfused blood, usually due to antibodies against minor blood group antigens, occurring days after the transfusion.

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    IgG antibodies

    Antibodies responsible for delayed hemolytic transfusion reactions, targeting minor blood group antigens.

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    What are isohemagglutinins?

    Antibodies (usually IgM) that are naturally present in the blood and target ABO blood group antigens that the individual doesn't possess.

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    Why do people with blood type A have anti-B antibodies?

    Because they don't have the 'B' antigen on their red blood cells, their immune system naturally produces antibodies against it, recognizing it as 'foreign' and potentially dangerous.

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    ABO incompatibility Transfusion Reaction

    A severe reaction that occurs when incompatible blood types are mixed during a transfusion. The recipient's antibodies attack the donor's red blood cells, leading to their destruction.

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    What are the symptoms of an immediate hemolytic transfusion reaction?

    Immediate symptoms include: hemoglobin in the urine, bilirubin buildup, fever, chills, nausea, clotting within blood vessels, and pain in the lower back.

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    What is a delayed hemolytic transfusion reaction?

    This reaction happens a few days after the transfusion, often due to antibodies against minor blood group antigens. It involves a slower destruction of red blood cells.

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    Goodpasture's Syndrome

    An autoimmune disease where antibodies target a collagen protein in the kidneys and lungs, causing inflammation and damage.

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    Pemphigus

    A blistering skin and mucosal disease caused by autoantibodies attacking desmogleins, proteins holding skin cells together.

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    Immune Complex-mediated Hypersensitivity (Type III)

    A hypersensitivity reaction where antibody-antigen complexes deposit in tissues, triggering inflammation and damage.

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    Desmogleins

    Adhesion proteins that glue together cells in the skin and mucosal layers.

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    What causes tissue damage in Type III hypersensitivity?

    Deposition of immune complexes activates complement and recruits neutrophils, leading to the release of damaging granules.

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    What causes hemolytic disease of the newborn?

    Hemolytic disease of the newborn (HDN) occurs when a mother who is Rh-negative carries an Rh-positive fetus. During pregnancy or delivery, fetal blood cells can enter the mother's circulation, triggering the production of Rh antibodies. In subsequent pregnancies with Rh-positive fetuses, these antibodies can cross the placenta and attack fetal red blood cells, causing anemia and other complications.

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    What is Rhogam and how does it work?

    Rhogam is an injection of anti-Rh antibodies given to Rh-negative mothers during pregnancy and after delivery. It works by preventing the mother's immune system from producing antibodies against Rh antigens present on fetal blood cells. This prevents the development of HDN in future pregnancies.

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    How do drugs cause hemolytic anemia?

    Certain drugs, like penicillin and some NSAIDs, can bind to proteins on red blood cell membranes. This creates a complex that the immune system recognizes as foreign. The body then produces antibodies against this complex, which can trigger complement-mediated lysis of red blood cells, leading to anemia.

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    What is thrombocytopenia and how can it be caused?

    Thrombocytopenia is a condition characterized by a low platelet count in the blood, making it difficult for the blood to clot. It can be caused by several factors, including decreased platelet production, increased platelet destruction, and abnormal distribution of platelets. Type II hypersensitivity reactions, where antibodies attack platelets, can contribute to increased destruction and cause immune-mediated thrombocytopenia.

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    What is purpura?

    Purpura is a condition characterized by areas of purplish discoloration on the skin. It is a prominent symptom of thrombocytopenia, caused by leakage of blood into the skin layers due to the inability to form clots effectively.

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    Antibody-dependent cell-mediated cytotoxicity (ADCC)

    Antibodies bind to target cells, marking them for destruction by NK cells.

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    Autoimmune hemolytic anemia

    Antibodies target erythrocytes (red blood cells), causing their destruction.

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    Warm antibodies

    Antibodies that attack red blood cells at normal body temperature.

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    Rhogam

    A medication given to Rh-negative mothers to prevent Hemolytic Disease of the Newborn by blocking the development of antibodies against Rh antigens in the fetus.

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    Immediate Hemolytic Transfusion Reaction

    A severe, rapid reaction that occurs shortly after a blood transfusion due to ABO incompatibility. It involves widespread destruction of red blood cells leading to symptoms like fever, chills, and hemoglobinuria.

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    Study Notes

    Type II Hypersensitivity

    • Clinical damage occurs when antibodies (Abs) bind directly to antigens (Ags) on cell surfaces, leading to cell lysis.
    • Involves antibody-mediated destruction of cells, mainly by IgM or IgG, not IgE.
    • Antibodies can attack mobile cells (leukocytes/RBCs) or fixed cells in tissues.
    • Antigens recognized can be foreign substances or autoantigens bound to the cell surface.
    • Pathological antibodies (autoantibodies) circulate freely in the periphery, binding to self-antigens, potentially causing autoimmune diseases.

    Examples of Type II Hypersensitivity

    • Blood transfusions reactions
    • Hemolytic disease of the newborn (Rh disease)
    • Anemias (some forms)
    • Drug reactions (drug-induced hemolytic anemia)
    • Platelet disorders
    • Tissue transplant reactions
    • Autoimmune disorders (not detailed)

    Mechanisms of Type II Hypersensitivity

    • Complement activation: Antibodies trigger complement activation, creating pores in the cell membrane, leading to cell lysis.
    • Antibody-dependent cell-mediated cytotoxicity (ADCC): Antibodies bind to foreign cells, marking them for destruction by immune cells (e.g., natural killer cells).
    • Antibody opsonization: Antibodies coat foreign cells, facilitating their phagocytosis by phagocytic cells. Complement proteins (e.g., C3b) may be involved.

    Hemolytic Anemias

    • Hemolytic anemia involves the destruction of red blood cells (RBCs).
    • Destruction can occur in blood vessels, spleen, or liver.
    • Autoantibodies or alloantibodies can cause this destruction.

    Autoimmune Hemolytic Anemias

    • Autoantibodies target the individual's own RBCs.
    • Antibodies can be warm (37°C) or cold (below 37°C), depending on optimal activity temperature.
    • Warm antibody-mediated hemolytic anemia is acute onset and often treated with glucocorticoids.
    • Cold antibody-mediated hemolytic anemia episodes might be triggered by cold weather.

    Alloimmune Hemolytic Anemias/Blood Transfusion Reactions

    • Individuals can mount an antibody response to different allelic forms of blood group antigens in transfused blood (foreign antigens).
    • Blood type antigens (ABH) are predominantly carbohydrates, not primarily proteins.
    • Exposure to common gut flora can trigger antibodies against blood group antigens.

    Thrombocytopenias (Type II HS)

    • Thrombocytopenia involves abnormally low platelet counts, leading to impaired blood clotting.
    • Causes include decreased platelet production, increased destruction, and abnormal distribution of platelets in the body.
    • Anti-platelet antibodies contribute to immune system-mediated thrombocytopenia, increasing the destruction of platelets.

    Other Examples of Type II HS

    • Ab-mediated rejection in solid tissue transplants: Pre-existing antibodies against donor MHC molecules can cause immediate rejection.
    • Goodpasture's syndrome: Autoantibodies target collagen in glomeruli in the kidney and alveoli in the lungs.
    • Pemphigus: Autoantibodies attack cell adhesion proteins (desmogleins).

    Immune Complex-Mediated Type III Hypersensitivity

    • Immune complexes (Ag-Ab) are typically cleared by phagocytic cells.
    • In some cases, complexes deposit in tissues, leading to inflammation and tissue damage.
    • The magnitude of the reaction depends on the quantity and distribution of immune complexes in the body.
    • Activation of mast cells, neutrophils, and macrophages releases inflammatory mediators, increasing vascular permeability leading to tissue damage.

    Type III Hypersensitivity (Localized and Generalized)

    • Localized reactions (e.g., Arthus reaction): Occur after injecting antigen.
    • Generalized reactions (e.g., serum sickness): Follow exposure to large amounts of antigen.

    Type IV (Delayed-Type) Hypersensitivity (DTH)

    • Cell-mediated hypersensitivity rather than antibody-mediated
    • Tissue damage primarily caused by effector T cells (e.g., Th cells, CTLs), macrophages.
    • Key example: Tuberculin reaction
    • Delayed-onset inflammation.
    • DTH response phases: Sensitization & Effector
    • Sensitization phase: Antigen exposure to develop specific T cells
    • Effector phase: Antigen encounters sensitized T cells to cause inflammation

    Contact Hypersensitivity (Type IV)

    • Secondary immune response to small, chemically reactive molecules binding to self-proteins in the skin's upper layers.
    • Examples: poison ivy, poison oak, hair dyes, nickel salts, latex, and certain drugs.

    Other characteristics of Type IV Hypersensitivity

    • Detected using skin tests (e.g., tuberculin test)
    • Characteristic skin lesions (e.g., redness, swelling) appear after a delayed period.

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    Description

    This quiz covers the mechanisms, clinical damage, and examples of Type II hypersensitivity reactions. Understand how antibodies interact with antigens, leading to various medical conditions, including autoimmune diseases and transfusion reactions. Test your knowledge on this crucial topic in immunology.

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