Type III Hypersensitivity Reactions Quiz
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Questions and Answers

What term is used to describe the phenomenon where an individual's immune response is triggered by haptens?

  • Hypersensitivity
  • Autoimmunity
  • Anaphylaxis
  • Immunogenicity (correct)

    • Which component of the immune system is most commonly associated with allergic reactions?

  • Mast cells (correct)
  • B lymphocytes
  • T lymphocytes
  • Neutrophils

    • Which of the following best defines serum sickness in relation to immune responses?

  • Type I hypersensitivity reaction
  • Immediate hypersensitivity reaction
  • Delayed-type hypersensitivity reaction
  • Type III hypersensitivity reaction (correct)

    • What is the primary mechanism behind anaphylaxis?

    <p>Degranulation of mast cells</p> Signup and view all the answers

    In relation to self-toxicity, which term refers to the immune system incorrectly attacking the body's own tissues?

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

    Which type of hypersensitivity reaction typically occurs upon first exposure to an allergen?

    <p>Type I hypersensitivity</p> Signup and view all the answers

    Which factor primarily influences the immunogenicity of a hapten?

    <p>Size and complexity</p> Signup and view all the answers

    What is a common outcome of a Type IV hypersensitivity reaction?

    <p>Delayed inflammatory response</p> Signup and view all the answers

    What characterizes the Arthus Reaction discovered by Nicolas Maurice Arthus?

    <p>Localized inflammatory response with pain and swelling.</p> Signup and view all the answers

    What is serum sickness primarily caused by?

    <p>Injection of foreign proteins or serum.</p> Signup and view all the answers

    Clemens Von Pirquet is credited with coining which term related to hypersensitivity?

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

    What is a key factor in transferring allergic sensitivity according to the work of Prausnitz and Kustner?

    <p>Reagin antibodies present in the serum.</p> Signup and view all the answers

    What role did Alexander Fleming discover lysozyme plays in the body?

    <p>Inhibits the growth of bacteria.</p> Signup and view all the answers

    What type of hypersensitivity reaction is primarily characterized by immune complex deposition?

    <p>Type III hypersensitivity</p> Signup and view all the answers

    What is the relationship between haptens and immunogenicity?

    <p>Haptens become immunogenic only when bound to larger proteins.</p> Signup and view all the answers

    What effect does the presence of an allergen have on an individual who has been previously sensitized?

    <p>An immediate and accelerated response.</p> Signup and view all the answers

    What condition arises when the body's immune cells fail to distinguish between self and non-self antigens?

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

    Which type of hypersensitivity reaction is characterized by an immediate allergic response, such as in anaphylaxis?

    <p>Type I hypersensitivity</p> Signup and view all the answers

    What is the primary mechanism behind serum sickness?

    <p>Formation of immune complexes</p> Signup and view all the answers

    What term describes small molecules that can bind to proteins and elicit an immune response only when attached to a larger carrier molecule?

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

    Which type of hypersensitivity reaction involves the formation of antigen-antibody complexes that can lead to tissue damage?

    <p>Type III hypersensitivity</p> Signup and view all the answers

    Which phenomenon describes the body's harmful immune response to its own tissues, often involving autoantibodies?

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

    What defines the mechanism of Type II hypersensitivity reactions?

    <p>Cell destruction via cytotoxic antibodies</p> Signup and view all the answers

    What is the biological significance of self-toxicity in the context of immunology?

    <p>It leads to tissue damage from autoimmune reactions</p> Signup and view all the answers

    What is the primary role of basophils in the immune response?

    <p>Histamine release during allergic reactions</p> Signup and view all the answers

    Which of the following cells is primarily involved in the immune response to parasitic infections?

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

    Which statement about mast cells is correct?

    <p>They release histamine upon degranulation.</p> Signup and view all the answers

    What distinguishes eosinophils from basophils in terms of their role?

    <p>Eosinophils play a specialized role in combating parasitic infections.</p> Signup and view all the answers

    How do basophils contribute to allergic reactions?

    <p>By increasing vascular permeability through histamine release</p> Signup and view all the answers

    What type of hypersensitivity reaction do mast cells primarily mediate?

    <p>Type I hypersensitivity</p> Signup and view all the answers

    What is a significant consequence of increased basophil numbers in the bloodstream?

    <p>Promotion of immediate hypersensitivity reactions</p> Signup and view all the answers

    Which factor is known to attract eosinophils to sites of allergic reactions?

    <p>Interleukin-5</p> Signup and view all the answers

    What distinguishes CD4 cells from CD8 cells in the context of T-cell development?

    <p>CD4 cells primarily assist in activating B cells.</p> Signup and view all the answers

    What is the primary function of the TDT enzyme in T-cells?

    <p>To facilitate the development of T-cell receptor diversity.</p> Signup and view all the answers

    Which process occurs in the thymus to ensure T-cells do not react to self-antigens?

    <p>Negative selection based on receptor affinity.</p> Signup and view all the answers

    What is a characteristic outcome when T lymphocytes recognize an antigen?

    <p>They differentiate into lymphoblasts.</p> Signup and view all the answers

    What immune response is primarily driven by the action of small lymphocytes that produce cytokines?

    <p>Cell-mediated immunity.</p> Signup and view all the answers

    What is the primary role of CD4+ T helper cells?

    <p>To act primarily on B cells</p> Signup and view all the answers

    Which statement accurately describes the function of Th1 cells?

    <p>They mediate cytotoxicity and local inflammatory reactions</p> Signup and view all the answers

    What differentiates suppressor T lymphocytes from T helper cells?

    <p>Suppressor T lymphocytes act to inhibit immune responses whereas T helper cells activate them</p> Signup and view all the answers

    What is the key mechanism behind the negative selection process in the maturation of T cells?

    <p>It eliminates thymocytes that do not recognize foreign antigens</p> Signup and view all the answers

    Which of the following best describes the role of memory T lymphocytes?

    <p>They are responsible for the anamnestic response upon re-exposure to an antigen</p> Signup and view all the answers

    What distinguishes double-positive thymocytes from double-negative thymocytes during T cell maturation?

    <p>Double-positive thymocytes express both CD4 and CD8 markers</p> Signup and view all the answers

    Which T cell subtype is primarily associated with Type IV hypersensitivity reactions?

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

    Which cytokine primarily influences the proliferation of double-negative thymocytes?

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

    What percentage of double-positive thymocytes typically survive the negative selection process?

    <p>1% to 2%</p> Signup and view all the answers

    What is the primary function of immune surveillance within the immune system?

    <p>To identify and eliminate cells that could lead to malignancy</p> Signup and view all the answers

    What is a common trigger for the production of autoimmune diseases?

    <p>An unknown trigger that leads to self-attack by antibodies</p> Signup and view all the answers

    Which characteristic of the immune system allows it to respond more effectively to previously encountered antigens?

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

    Immunologic deficiency disorders primarily affect which aspect of the immune system?

    <p>The body's ability to produce antibodies</p> Signup and view all the answers

    Hypersensitivity reactions can lead to an abnormal immune response. Which of the following best describes this effect?

    <p>The immune system overreacting to harmless substances</p> Signup and view all the answers

    Which characteristic ensures that the immune system can differentiate between various foreign molecules?

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

    In the context of hypersensitivity, what does the term 'allergy' typically refer to?

    <p>An abnormal reaction to typically harmless substances</p> Signup and view all the answers

    What might be a consequence of immune system malfunctioning in relation to malignancy?

    <p>Failure to detect atypical cell growth</p> Signup and view all the answers

    How might immunologic deficiency disorders impact energy levels in individuals?

    <p>They can contribute to fatigue due to increased susceptibility to infections</p> Signup and view all the answers

    What is a potential negative consequence of the immune system's defense mechanisms?

    <p>Development of autoimmunity</p> Signup and view all the answers

    What role does diversity in the immune system play?

    <p>It enables the immune system to respond to various pathogens.</p> Signup and view all the answers

    What is the function of contraction in the immune response?

    <p>To allow the immune system to return to homeostasis post-infection.</p> Signup and view all the answers

    How does non-reactivity to self contribute to immune function?

    <p>It prevents the immune response from incorrectly attacking the host's own tissues.</p> Signup and view all the answers

    What does the term 'specialization' refer to in the context of the immune system?

    <p>The generation of responses optimal for different types of microbes.</p> Signup and view all the answers

    What is the primary site for the maturation of T lymphocytes?

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

    What is the major outcome of immune deficiency disorders?

    <p>Increased susceptibility to infections.</p> Signup and view all the answers

    In what way does mobility impact the immune system?

    <p>It facilitates local reactions for systemic protection.</p> Signup and view all the answers

    Which of the following best describes the lymphatic system's function?

    <p>It transports antigens from tissues to secondary lymphoid organs.</p> Signup and view all the answers

    Which of the following statements is true regarding the immune system's homeostasis?

    <p>It is the balance between immune activation and contraction.</p> Signup and view all the answers

    How does the immune system ensure effective immune surveillance?

    <p>By continuously generating a large number of lymphocytes.</p> Signup and view all the answers

    What role does fibrinogen play following tissue injury?

    <p>It forms a clot that provides strength to the wound.</p> Signup and view all the answers

    Which of the following best describes the positive mechanism of chemotaxis?

    <p>Movement of cells toward the source of stimulation.</p> Signup and view all the answers

    Which complement protein is considered the most potent enhancer of phagocytosis?

    <p>C3b</p> Signup and view all the answers

    What is the sequence of steps in the phagocytosis process?

    <p>Opsonization, engulfment, digestion, degranulation.</p> Signup and view all the answers

    What characterizes the activity of neutrophils during acute inflammation?

    <p>They are mobilized by chemotaxins and last for 24-48 hours.</p> Signup and view all the answers

    Which term best describes the process of leukocyte emigration from capillaries?

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

    What is the outcome of the fusion between the phagosome and hydrolytic enzymes?

    <p>Creation of the phagolysosome.</p> Signup and view all the answers

    Which activity is NOT enhanced by integrins during immune responses?

    <p>Formation of clots at the injury site.</p> Signup and view all the answers

    What is the primary role of monocytes after they migrate from blood to tissues?

    <p>To differentiate into macrophages</p> Signup and view all the answers

    Which component primarily activates macrophages in the immune response?

    <p>Contact with pathogens or cytokines</p> Signup and view all the answers

    During which process do monocytes primarily take on a phagocytic role?

    <p>After they differentiate into macrophages</p> Signup and view all the answers

    What is a major consequence of increased eosinophil activity in response to parasitic infections?

    <p>Production of major basic proteins</p> Signup and view all the answers

    What critical function does heparin serve in the immune system?

    <p>Inhibits blood clotting at sites of inflammation</p> Signup and view all the answers

    Which type of immune cells are primarily responsible for the secretion of cytokines that facilitate inflammation?

    <p>T lymphocytes</p> Signup and view all the answers

    What triggers the migration of monocytes to tissues during an immune response?

    <p>Chemotactic signals from other immune cells</p> Signup and view all the answers

    At what time frame do monocytes typically migrate to tissues after entering the bloodstream?

    <p>Within 30 hours</p> Signup and view all the answers

    What type of immune response do phagocytes primarily engage in?

    <p>Pathogen clearance through ingestion</p> Signup and view all the answers

    Which factor plays a role in the activation of basophils during hypersensitivity reactions?

    <p>IgE antibodies bound to allergens</p> Signup and view all the answers

    What is the primary end product of complement activation?

    <p>Cell lysis</p> Signup and view all the answers

    Which process best describes the movement of cells toward a chemical gradient during an immune response?

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

    Which of the following is NOT a function of complement proteins?

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

    During which step of phagocytosis do cytoplasmic granules fuse with the phagosome membrane?

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

    Which type of nitric oxide species is rapidly released by neutrophils to kill ingested microorganisms?

    <p>Superoxide anion</p> Signup and view all the answers

    What initiates the process of phagocytosis in response to tissue damage?

    <p>Physical contact with microorganisms</p> Signup and view all the answers

    Which receptor is involved in the adherence phase of phagocytosis?

    <p>Complement receptor</p> Signup and view all the answers

    What is the primary mechanism of neutrophils for destroying ingested pathogens?

    <p>Respiratory burst</p> Signup and view all the answers

    What type of proteins contribute to the opsonization process?

    <p>C3 complement proteins</p> Signup and view all the answers

    What is the primary function of fibrinogen in the context of an immune response?

    <p>To facilitate the formation of tissue repair and clotting</p> Signup and view all the answers

    Which mechanism best describes how immune cells move toward a site of infection?

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

    Which role does the complement system primarily play in immune responses?

    <p>Enhancing the ability of antibodies and phagocytic cells to clear pathogens</p> Signup and view all the answers

    Which of the following steps is NOT part of the phagocytosis process?

    <p>Secretion of antibodies against the pathogen</p> Signup and view all the answers

    What is a key characteristic of neutrophil activity during an immune response?

    <p>They release enzymes and reactive oxygen species to kill pathogens</p> Signup and view all the answers

    Which process is primarily responsible for attracting neutrophils to sites of injury or infection?

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

    Which component plays a critical role in the final outcome of complement activation?

    <p>Cell lysis</p> Signup and view all the answers

    What is the primary function of neutrophils in the immune system?

    <p>Engaging in phagocytosis</p> Signup and view all the answers

    Which cytokines are primarily involved in the communication between immune cells during an immune response?

    <p>Interferons and interleukins</p> Signup and view all the answers

    What initiates the process of phagocytosis in cells like neutrophils?

    <p>Signal transduction pathways</p> Signup and view all the answers

    Which cellular component directly destroys tumor and infected cells in the immune response?

    <p>Natural killer cells</p> Signup and view all the answers

    Which type of immune cell has the shortest lifespan and is primarily involved in acute inflammatory responses?

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

    What is the primary role of eosinophils in the immune system?

    <p>Suppressing inflammatory reactions</p> Signup and view all the answers

    Which process is characterized by the formation of channels in the target cell membrane by proteins such as perforin?

    <p>Cell lysis</p> Signup and view all the answers

    How do cytokines contribute to the immune response during infections?

    <p>By facilitating communication between immune cells</p> Signup and view all the answers

    Which type of antigen is exclusively found within genetically identical individuals, such as identical twins?

    <p>Syngeneic antigen</p> Signup and view all the answers

    Which factor does NOT directly influence the immunogenicity of a substance?

    <p>Duration of storage</p> Signup and view all the answers

    What is the primary role of an epitope in the immune response?

    <p>To trigger the production of antibodies</p> Signup and view all the answers

    Which of the following is NOT a common route for immunization?

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

    Which characteristic primarily differentiates immunogens from antigens?

    <p>Capability to stimulate antibody production</p> Signup and view all the answers

    Which statement accurately describes the nature of epitopes?

    <p>A single antigen may contain multiple distinct epitopes.</p> Signup and view all the answers

    What is a primary characteristic that distinguishes haptens from complete antigens?

    <p>Haptens are not observed in vitro reactions.</p> Signup and view all the answers

    Which classification of antigens is characterized by their ability to induce an immune response but cannot invoke antibody production?

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

    In the classification based on origin or source, which type of antigen is described as found in genetically identical individuals?

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

    Which of the following factors does NOT contribute to the immunogenicity of an antigen?

    <p>Color of the antigen</p> Signup and view all the answers

    What is a distinct feature of precipitinogens compared to other types of antigens?

    <p>They react with soluble precipitins.</p> Signup and view all the answers

    What defines the association between a carrier and a determinant group in the context of antigen composition?

    <p>The carrier is responsible for antibody production.</p> Signup and view all the answers

    Which of the following best describes the relationship between antigens and their respective antibodies?

    <p>Different antibodies can recognize the same antigen.</p> Signup and view all the answers

    What term describes the production of antibodies by an individual against an antigen they possess?

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

    What characterizes the effect of superantigens on T-cell activation?

    <p>They induce nonspecific activation of T-cells.</p> Signup and view all the answers

    Which factor does NOT contribute to the immunogenicity of an antigen?

    <p>The age of the individual</p> Signup and view all the answers

    Which of the following statements about immunologic adjuvants is accurate?

    <p>They enhance T-cell activation and expression of costimulators.</p> Signup and view all the answers

    Which phenomenon allows for the cross-reaction of antigens across different species?

    <p>Heterophilic reaction</p> Signup and view all the answers

    What is the primary role of epitope in the immune response?

    <p>It serves as the binding site for antibodies or T-cell receptors.</p> Signup and view all the answers

    In the context of isosensitization, what is the primary source of the antigens?

    <p>The same species</p> Signup and view all the answers

    What role do heterogenetic antigens play in immune responses?

    <p>They can cause cross-reactions in unrelated species.</p> Signup and view all the answers

    How do adjuvants primarily enhance the immune response?

    <p>By increasing the number of cells involved in the immune response</p> Signup and view all the answers

    Which route of immunization is generally considered to provide the most potent immune response?

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

    Which characteristic of an antigen is most critical for it to be recognized as foreign by the immune system?

    <p>High molecular weight</p> Signup and view all the answers

    What is primarily responsible for the variability in immunogenicity of a hapten?

    <p>The carrier protein it is attached to</p> Signup and view all the answers

    Which type of T-dependent antigen is mainly comprised of proteins?

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

    The effectiveness of an antigen is increased with which of the following factors?

    <p>Higher degree of foreignness</p> Signup and view all the answers

    What aspect of the physical nature of an antigen contributes to its structural stability?

    <p>Complexity of the antigen</p> Signup and view all the answers

    Which of the following plays a critical role in the presentation of T-dependent antigens to the immune system?

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

    Which characteristic must an antigen possess to effectively induce an immune response?

    <p>High degree of specificity</p> Signup and view all the answers

    What defines a hapten in immunology?

    <p>A low molecular weight compound that needs a carrier to provoke an antibody response</p> Signup and view all the answers

    Which factor is least likely to enhance the immunogenicity of an antigen?

    <p>Simplicity of the structural design</p> Signup and view all the answers

    What type of graft involves the transplantation of tissues between different individuals of the same species?

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

    Which of the following molecules is considered an excellent immunogen due to its molecular weight?

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

    What is the most significant factor influencing the immunogenicity of a molecule?

    <p>Size of the antigen</p> Signup and view all the answers

    Which type of epitope is primarily associated with the immune response?

    <p>Both linear and conformational epitopes</p> Signup and view all the answers

    Polysaccharides are generally considered incomplete immunogens due to their lack of what characteristic?

    <p>Chemical diversity</p> Signup and view all the answers

    Which immune response is primarily triggered by immunogens with a molecular weight greater than 10,000 Daltons?

    <p>Good immunogenic response</p> Signup and view all the answers

    Which of the following is considered non-immunogenic due to its relative simplicity?

    <p>Nucleic acids</p> Signup and view all the answers

    What type of graft involves tissue transfer between genetically identical individuals?

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

    The component of the immune system that typically provides the strongest immunogenic response consists mainly of which biochemical unit?

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

    Study Notes

    Historical Contributions to Immunology

    • Nicolas Maurice Arthus discovered the Arthus Reaction, a localized inflammatory response linked to type III hypersensitivity, exhibiting symptoms like pain, swelling, and potential necrosis at injection sites.
    • Clemens von Pirquet and Bela Schick identified serum sickness in 1905, a type III hypersensitivity reaction from heterologous serum, and coined the term "allergy" in 1906 to describe altered reactivity to allergens.
    • Carl Prausnitz and Heinz Kustner demonstrated the cutaneous allergic reaction in 1921 by transferring allergic sensitivity through serum from an allergic individual to a normal individual, utilizing reagin antibodies.
    • Alexander Fleming discovered lysozyme in 1921 and penicillin in 1928; the latter revolutionized medicine as a powerful antibacterial agent, famously called a “miracle drug” during WWII.

    Overview of Immunology

    • Immunology is defined as the study of the body’s resistance to infectious diseases and the host's reactions to foreign substances.
    • Key areas of immunology include the body’s defense mechanisms, responses to pathogens, and interactions with foreign substances.

    Subdivisions of Immunology

    • Immunity: Refers to processes that protect the body against foreign organisms or molecules.
    • Infectious Disease: A condition caused by harmful microorganisms that disrupt normal bodily functions.
    • Hypersensitivity: An adverse tissue response due to antigenic stimulation, leading to damaging conditions.
    • Autoimmunity: When immune cells mistakenly attack the body’s own antigens, mistaking them for foreign invaders.
    • Immunodeficiency: A malfunction in the immune system that hampers the ability to recognize and respond to foreign antigens.

    Forms of Immunity

    • Specific Immunity: Also known as acquired immunity, it develops through exposure to various antigens.
    • Nonspecific Immunity: Also referred to as innate immunity; it consists of general defense mechanisms present from birth, including physical barriers and immune responses.

    Historical Figures in Microbiology and Immunology

    • Theodore Schwann (1798): Established the role of microbes in fermentation and putrefaction through sugar fermentation studies, linking yeast to fermentation processes.
    • Friedrich Gustav Jakob Henle (1840): Championed the germ theory of disease and detailed methodologies in his essay on miasma and contagion, discovering anatomical structures in the kidney.
    • Ernst Haeckel (1862): First to observe phagocytosis, identifying white blood cells' role in digesting particles.
    • Joseph Lister (1867): Known as the Father of Antiseptic Surgery, pioneering aseptic techniques using carbolic acid (phenol) in surgical practices.
    • Robert Koch (1876): Established Koch’s Postulates detailing the criteria for linking specific pathogens to diseases, notably Tuberculosis, Cholera, and Anthrax.
    • Paul Ehrlich (1877): Recognized mast cells as crucial cells involved in allergic responses.

    Basophils

    • Contain heparin, an anticoagulant that prevents blood clotting.
    • Play a crucial role in immediate hypersensitivity reactions, such as allergies.
    • Present in large quantities during some cell-mediated delayed reactions.
    • Characterized by bilobed nuclei and cytoplasmic granules.
    • Found in low numbers in peripheral blood but act similarly to mast cells.
    • Involved in Type I hypersensitivity; IgE binds to basophils upon allergen exposure.
    • Increased basophil counts contribute to inflammation and immediate hypersensitivity responses.

    Eosinophils

    • Major effector cells in the immune system, pivotal for combating helminth and other parasitic infections.
    • Can exacerbate allergic diseases through inflammatory processes.
    • Release histamine when stimulated, potentially triggering asthma; eosinophil levels rise during allergic reactions and parasitic infections.
    • Reside in tissues at sites of immune responses triggered by IgE antibodies.
    • Phagocytize antigen-antibody complexes and produce enzymes that degrade mediators of hypersensitivity.
    • Release histamine and Platelet Aggregating Factor (PAF) to modulate hypersensitivity reactions.

    Mast Cells

    • Located in various tissues such as skin, connective tissues, and mucosal epithelium of respiratory, genitourinary, and digestive tracts.
    • Heavily granulated with granules containing histamine; degranulation initiates allergic and inflammatory responses.
    • Share functional similarities with basophils, but mast cells are primarily tissue-resident.

    T Helper Cells

    • CD4+ cells identify specific antigens in conjunction with class II MHC molecules.
    • Primarily activate B cells for antibody production.
    • Th1 cells mediate cytotoxicity and local inflammation.
    • Th2 cells promote IgE, IgA, and IgG1 production.

    T Lymphocyte Types

    • Inducer T Lymphocytes (CD4+): Activate other T cells and macrophages by recognizing Class I MHC-associated antigens.
    • Suppressor T Lymphocytes (CD8+): Inhibit immune responses; release factors that suppress immune activity.
    • Delayed-Type Hypersensitivity Effector Cells: CD4+ lymphocytes involved in Type IV hypersensitivity reactions.
    • Memory T Lymphocytes (CD4+): Responsible for anamnestic responses and booster immunization.

    T Cell Maturation Process

    • Thymocytes mature in the thymus; 60-80% of circulating lymphocytes are T cells.
    • Initial double negative thymocytes proliferate under Interleukin-7 influence.
    • Transition to double positive thymocytes occurs when both CD4 and CD8 antigens are expressed.
    • Positive selection allows only functional TCR-expressing cells to survive; rigorous negative selection ensures self-tolerance.
    • Only 1-2% of double positive thymocytes survive through the selection processes.

    Immune System Functions

    • Defense against infections and harmful substances.
    • Maintains homeostasis of body systems such as temperature and hydration.
    • Immune surveillance detects and destroys early tumor formations.
    • Abnormal responses can lead to hypersensitivity or autoimmune diseases.

    Characteristics of the Immune System

    • Specificity: Distinct antigens elicit specific immune responses.
    • Memory: Enhanced immune response upon re-exposure to the same antigen.
    • Non-reactivity to self: Prevents damage to host tissues during immune responses.

    Lymphoid Organs

    • Primary lymphoid organs: Sites for T and B cell maturation.
      • Bone Marrow: Primary site for blood cell production and B cell maturation.
      • Thymus: Responsible for T lymphocyte maturation, shrinking with age.

    Immune System Overview

    • Composed of organs, cells, and proteins that protect against pathogens and malignancy.
    • Offers natural and acquired resistance to infections while potentially causing autoimmune disorders.
    • Involves a complex interplay between different immune cells and responses to varied antigens.

    Chemotaxins and Chemokines

    • Chemotaxins are substances released by bacteria, injured tissues, and leukocytes, prompting neutrophils and other white blood cells (WBC) to migrate to injury sites.
    • Diapedesis refers to the movement of cells from capillaries to tissues.
    • Chemokines are cytokines involved in activating WBCs during their migration across the endothelium; can be positive (toward stimulus) or negative (away from stimulus).

    Job's Syndrome and Lazy Leukocyte Syndrome

    • Job's Syndrome: Phagocytes have normal movement but exhibit abnormal chemotactic activity.
    • Lazy Leukocyte Syndrome: Both random and chemotactic activities of phagocytes are impaired.

    Phagocytosis

    • Engulfment occurs via active amoeboid motion.
    • Opsonization enhances phagocytosis by coating particles with plasma factors known as opsonins.

    Opsonins

    • Opsonins interact with bacterial surfaces, making them more acceptable to phagocytes.
    • Examples include complement proteins (especially C3b), antibodies, fibrinonectin, leukotrienes, and tuftsin.
    • Result of engulfment is the formation of phagosomes or phagocytic vacuoles.

    Digestion

    • Phagolysosome is formed through the fusion of phagosomes and hydrolytic enzymes, allowing for the breakdown of foreign materials.

    Factors Enhancing Phagocytosis

    • Integrins enhance cell interactions during immune responses.
    • Opsonins like C3b promote the binding of phagocytes to antibody-coated targets.
    • Fibronectin facilitates the adhesion of neutrophils to target cells.
    • Leukotrienes and tuftsin play roles in chemotaxis and phagocytic activity.

    Antigen Destruction

    • Phagolysosomes contain defensins, lactoferrin, and lysozyme, which contribute to microbial destruction.
    • Nitric oxide produced by activated macrophages is toxic to microorganisms.

    Inflammation

    • Inflammation is the body's response to injury, protecting against foreign invaders while minimizing tissue damage.
    • Key signs include:
      • Rubor: redness
      • Tumor: swelling
      • Calor: heat
      • Dolor: pain
      • Functio laesa: loss of function

    Stages of Inflammation

    • Vascular Response: Mast cells release histamine leading to blood vessel dilation and increased permeability, causing redness, heat, swelling, and pain.
    • Cellular Response:
      • Neutrophils: primary cells in acute inflammation, mobilized quickly.
      • Monocytes/Macrophages: involved in chronic inflammation, arriving later and forming pus.

    Cellular Resolution and Repair

    • Fibroblasts proliferate to replace damaged cells.
    • Abscess formation leads to some loss of function, while granulomas are caused by T-cell accumulation.

    Natural Immunity

    • Comprises innate/non-specific immunity, involving cellular and humoral components.
    • External defenses include skin and mucous membranes, while internal defenses utilize NK cells and phagocytosis.

    Acquired Immunity

    • Adaptive immunity relies on genetic events and cellular growth.
    • Eosinophils kill parasites and produce major basic proteins; basophils release histamine and heparin.

    Cellular Components of Immunity

    • Monocytes differentiate into macrophages, playing a role in phagocytosis and antigen presentation.
    • Macrophages are activated by microorganisms or T-cell cytokines, aiding in immune responses.

    Physiological Factors Influencing Immunity

    • Body temperature and oxygen tension can affect pathogen proliferation.
    • Hormonal balance impacts inflammatory responses, with extremes of age showing sub-optimal immunity.

    Second Line of Defense Components

    • Cellular components include phagocytes like neutrophils and monocytes.
    • Natural Killer (NK) cells can destroy tumor and virus-infected cells.
    • Humoral components include cytokines and the complement system, which facilitates cell destruction through lysis.

    Lysozyme and Properdin

    • Lysozyme hydrolyzes bacterial cell walls and is found in various body fluids.
    • Properdin exhibits bactericidal effects in conjunction with complement proteins.

    Phagocytosis Process

    • Involves initiation through contact, followed by chemotaxis, engulfment (forming phagosomes and phagolysosomes), and digestion of target microorganisms.

    Types of Interferons

    • IFN-beta is produced by fibroblasts and affected by viruses; helps in immune responses.
    • IFN-gamma is secreted by lymphocytes and is crucial for specific immune responses against pathogens.

    Tumor Necrosis Factor (TNF)

    • TNF is cytotoxic to tumor and virus-infected cells, with two types: TNF-alpha (produced by macrophages) and TNF-beta (produced by CD4+ and CD8+ cells).

    Interleukins

    • A group of proteins that mediate cell communication and immune responses.
    • Different interleukins (e.g., IL-1, IL-2, IL-3) have distinct roles in inflammation, T-cell activation, and hematopoiesis.

    Acute Phase Reactants

    • Proteins that increase during infection or injury include C-reactive Protein (CRP), Serum Amyloid A (SAA), and others.

    Epitopes and Antigens

    • Epitopes are specific parts of an antigen that interact with antibodies; a single antigen may possess multiple epitopes.
    • Each epitope is recognized by a distinct antibody.

    Parts of an Antigen

    • Carrier: The main structure of the antigen, typically proteins, that can induce an immune response.
      • Comprises 5 to 7 amino acids or equivalent monosaccharide residues.
    • Determinant Group: The reactive part of an antigen that can interact with antibodies but does not induce antibody production on its own.

    Classification of Antigens

    • Based on Structure and Function:

      • Complete Antigens: Exhibit full immunogenic properties.
      • Hapten: Low molecular weight compounds that can only elicit an immune response when attached to a carrier; categorized into:
        • Simple: Monovalent, single determinant.
        • Complex: Multivalent, multiple determinants.

    • Based on Reaction:

      • Agglutinogen: Causes agglutination when acted upon by antibodies.
      • Precipitinogen: Reacts with soluble precipitins leading to precipitation.
      • Virus: Neutralized by specific neutralizing antibodies.
      • Toxin: Poisonous substances neutralized by antitoxins.
      • Allergen: Triggers allergic reactions by antibody interactions.
      • Anaphylactogen: Allergen involved in severe allergic (anaphylactic) reactions.

    • Based on Origin:

      • Autologous: Antigens from the same individual.
      • Syngeneic: Identical individuals, such as identical twins.
      • Allogenic: From different individuals of the same species.
      • Xenogeneic: From different species (heterologous).

    Immunogenicity and Molecular Weight

    • Higher molecular weight correlates with better immunogenicity; molecules under 5,000 Daltons are typically non-immunogenic.
    • Immunogenic categories based on molecular weight include:
      • Potential Immunogen: >10,000 Daltons (e.g., serum albumin).
      • Good Immunogen: >40,000 Daltons (e.g., gamma globulin).
      • Excellent Immunogen: >1,000,000 Daltons (e.g., hemocyanin).

    Chemical Composition and Complexity

    • Complexity increases immunogenic potential; higher complexity often leads to stronger immune responses.
    • Proteins: Most effective immunogens.
    • Glycoproteins: Composed of protein and carbohydrate chains (e.g., blood group antigens A, B, Rh).
    • Polysaccharides: Often incomplete immunogens, with two forms being pure polysaccharides and lipopolysaccharides (endotoxins).
    • Nucleic Acids: Generally non-immunogenic due to simplicity.
    • Lipids: Mostly non-immunogenic, some can act as haptens.

    Administration Factors

    • Route: Intravenous and intraperitoneal are effective; intradermal offers the strongest response.
    • Dosage: Smaller doses result in less immune response.
    • Degradability: Immunogens need to be degraded for immune system recognition; involved are T-dependent (proteins) and T-independent (carbohydrates) antigens.

    Basic Characteristics of Antigens

    • Must be foreign to the body and possess high molecular weight.
    • Needs entry into the body and usually a protein or complex polysaccharide.
    • Should exhibit a high level of specificity.

    Physical Nature of Antigens

    • Foreignness: Degree to which immune system identifies antigens as non-self.
    • Degradability: Sufficient amounts needed for immune response activation.
    • Structural Stability: Unstable structures yield poor antigenic response.
    • Complexity: Greater complexity enhances effectiveness as an antigen.

    Sensitization Types

    • Isosensitization: Antibody production from antigens introduced from the same species.
    • Heterosensitization: Antibody production in response to antigens from different species.
    • Autosensitization: Antibody production against self-antigens.

    Superantigens

    • Class of antigens that non-specifically activate T-cells, leading to extensive cytokine release; produced by certain pathogens (e.g., Staphylococcal and Streptococcal toxins).

    Immunologic Adjuvants

    • Substances that enhance T-cell activation and co-stimulator expression; they cannot induce immune response alone.
    • Adjuvants increase the involvement of immune system cells, boosting responses to vaccines and immunogenic substances.

    Definitions

    • Antigen: Any substance recognized as foreign and capable of reacting with antibodies or receptors.
    • Immunogen: Macromolecules that induce immune responses; all immunogens are antigens, but not all antigens are immunogenic.

    Properties of Antigens

    • Immunogenicity: Ability to induce an immune response, leading to antibody production.
    • Antigenicity: The capability to react specifically with antibodies.

    Factors Affecting Immunogenicity

    • Foreignness, molecular weight, chemical composition and complexity, route and dosage timing, and degradability all influence the effectiveness of immunogenic response.

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    Description

    This quiz covers the findings of Nicolas Maurice Arthus and his discovery of the Arthus reaction, as well as the contributions of Clemens von Piquet and Bela Schick on serum sickness. Explore the details of localized inflammatory responses and their characteristics. Test your knowledge about type III hypersensitivity and its historical significance.

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