Immunology Year 1: Extracellular Infection Responses
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Questions and Answers

What type of immunoglobulin is predominantly produced in response to Streptococcus pyogenes?

  • IgM
  • IgA
  • IgE
  • IgG (correct)

    • What is the primary site for long-lived plasma cells generated in response to protein antigens?

  • Gut
  • Bone marrow (correct)
  • Lymph nodes
  • Spleen

    • Which type of T helper cell is associated with the antibody response to streptococci?

  • Th2
  • Th1
  • Th17 (correct)
  • Treg

    • In contrast to the response to protein antigens, what is the main feature of antibody production in response to toxins?

    <p>Minimal isotype switching</p> Signup and view all the answers

    Which cytokine is linked to the activation of Th17 responses?

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

    What is a distinguishing feature of the immune response to Staphylococcus aureus compared to Streptococcus pyogenes?

    <p>Isotype switching to produce IgM</p> Signup and view all the answers

    Which statement is true about memory B cells in response to Streptococcus pyogenes?

    <p>They reside in marginal zones of secondary lymph organs.</p> Signup and view all the answers

    Which antibody function is crucial in preventing the entrance of Streptococcus into host tissues?

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

    What condition is defined as a reduction or loss of splenic function?

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

    Which antibodies are primarily produced by short-lived plasma cells in the spleen?

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

    What is a common cause of hyposplenism related to surgical intervention?

    <p>Surgical removal of the spleen</p> Signup and view all the answers

    Which of the following is NOT a recommended vaccine for patients with hyposplenism?

    <p>Hepatitis B</p> Signup and view all the answers

    What do eosinophil granules contain that is specifically harmful to parasites?

    <p>Toxic proteins</p> Signup and view all the answers

    What is the primary goal of managing hyposplenism in patients?

    <p>To prevent recurrent bacterial infections</p> Signup and view all the answers

    What type of clinical condition is functional hyposplenism associated with?

    <p>Coeliac disease</p> Signup and view all the answers

    In the context of TH2 associated diseases, what is a key indicator of increased susceptibility to asthma?

    <p>High levels of IgE</p> Signup and view all the answers

    What is one method used to monitor patients with hyposplenism?

    <p>Annual measurement of antibody titers</p> Signup and view all the answers

    What role do mast cells play regarding infections?

    <p>They assist with the removal of killed parasites.</p> Signup and view all the answers

    Which interleukins are commonly associated with TH2 responses?

    <p>IL-4 and IL-5</p> Signup and view all the answers

    What type of infection does the spleen help clear from the bloodstream?

    <p>Extracellular bacterial infections</p> Signup and view all the answers

    What is one consequence of increased mast cell activity?

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

    What should individuals at risk carry or wear to identify their condition?

    <p>Splenectomy card or Medic-Alert bracelet</p> Signup and view all the answers

    Which cytokine is primarily involved in T cell differentiation towards the Th2 subset?

    <p>IL-4</p> Signup and view all the answers

    What do toll-like receptors (TLRs) primarily recognize?

    <p>Pathogen-associated molecular patterns (PAMPs)</p> Signup and view all the answers

    Which type of infections are Th2 cells particularly important against?

    <p>Helminth infections</p> Signup and view all the answers

    What is one of the key functions of IL-4 in immune response?

    <p>Isotype switching towards IgE and IgG</p> Signup and view all the answers

    What do mast cell granules primarily contain to combat helminths?

    <p>Proteases and other harmful substances</p> Signup and view all the answers

    What is the role of histamine in the immune response against helminths?

    <p>Increasing gut mucus secretion and promoting peristalsis</p> Signup and view all the answers

    Which pathogen is NOT listed as an example of a helminth infection?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    Which interleukin is known for recruiting mast cells and eosinophils?

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

    What triggers inflammation in the innate immune response?

    <p>Cytokine release such as IL-1 and TNF</p> Signup and view all the answers

    Which TLR is responsible for recognizing the surface of Streptococcus?

    <p>TLR2</p> Signup and view all the answers

    What are the main cytokines produced by macrophages?

    <p>TNF and IL-1</p> Signup and view all the answers

    What role do antibodies play against Streptococcus?

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

    Which TLR is NOT involved in recognizing Streptococcus?

    <p>TLR6</p> Signup and view all the answers

    Which cytokine is primarily associated with acute inflammation by macrophages?

    <p>TNF-alpha</p> Signup and view all the answers

    Which mechanism is NOT a function of antibodies against Streptococcus?

    <p>Direct lysis of bacteria</p> Signup and view all the answers

    What type of immune response do antibodies mediate against Streptococcus?

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

    Which TLR is involved in recognizing a broader range of pathogens, including viruses?

    <p>TLR3</p> Signup and view all the answers

    Which of the following is a characteristic of extracellular infections?

    <p>They multiply outside of host cells.</p> Signup and view all the answers

    What role do antibodies play in response to extracellular infections?

    <p>They help in the elimination of extracellular pathogens.</p> Signup and view all the answers

    Which of the following cells is primarily involved in detecting extracellular infections?

    <p>Antigen-presenting cells</p> Signup and view all the answers

    What condition may result from the absence of spleen function?

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

    Which of the following organisms is an example of a helminth involved in extracellular infection?

    <p>Schistosoma mansoni</p> Signup and view all the answers

    Which immune response is coordinated between innate and adaptive immunity during extracellular infections?

    <p>Antigen presentation to T cells is necessary.</p> Signup and view all the answers

    Complement activation contributes to the immune response by which of the following mechanisms?

    <p>Enhancing phagocytosis.</p> Signup and view all the answers

    Inflammatory responses during extracellular infections are important for which of the following?

    <p>Attracting immune cells to the site of infection.</p> Signup and view all the answers

    Which of the following types of infections require a distinct type of immune response?

    <p>Extracellular infections and fungal infections.</p> Signup and view all the answers

    Which immune cells are important for the inflammatory response to extracellular infections?

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

    What is a key feature of B cell memory after an extracellular infection?

    <p>B cells generate a fast response upon reinfection.</p> Signup and view all the answers

    Which of these is NOT considered a constituent of innate immunity?

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

    Which type of infections necessitates cytotoxic T cells for an effective immune response?

    <p>Intracellular infections</p> Signup and view all the answers

    What type of immune response is specifically involved in clearing extracellular bacteria?

    <p>Humoral immunity</p> Signup and view all the answers

    What type of antibody is primarily produced in response to non-protein toxins?

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

    What is the main site where long-lived plasma cells reside after responding to protein antigens?

    <p>Bone marrow</p> Signup and view all the answers

    Which characteristic distinguishes the B cell response to Streptococcus pyogenes from that to other types of antigens?

    <p>Generation of memory B cells</p> Signup and view all the answers

    Which antibody function is essential for opsonization against Streptococcus pyogenes?

    <p>Promotion of phagocytosis</p> Signup and view all the answers

    What type of B cell response is characterized by minimal isotype switching and the generation of short-lived plasma cells?

    <p>Response to non-protein toxins</p> Signup and view all the answers

    In which area do memory B cells primarily reside after responding to Streptococcus pyogenes?

    <p>Marginal zones of secondary lymph organs</p> Signup and view all the answers

    What type of antibodies primarily neutralize and activate complement against Streptococcus?

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

    In the immune response to Streptococcus, what is the role of neutralizing antibodies?

    <p>To prevent bacterial entry and neutralize exotoxins</p> Signup and view all the answers

    What are the immediate health measures recommended for an individual with asplenia?

    <p>Prophylactic antibiotics and immunisation</p> Signup and view all the answers

    Which immunization is NOT recommended for patients with hyposplenism?

    <p>Rabies vaccine</p> Signup and view all the answers

    What is a primary consequence of hyposplenism on the immune system?

    <p>Reduced ability to clear extracellular bacterial infections</p> Signup and view all the answers

    What is the role of the spleen in developing B cells?

    <p>Completion of B cell maturation</p> Signup and view all the answers

    Which of the following conditions is a cause of functional hyposplenism?

    <p>Sickle-cell anaemia</p> Signup and view all the answers

    What is the primary goal of managing hyposplenism?

    <p>Reducing bacterial infections</p> Signup and view all the answers

    What is a characteristic feature of short-lived plasma cells in the context of hyposplenism?

    <p>They secrete large amounts of IgM antibodies</p> Signup and view all the answers

    Why is it important to measure antibody titers annually in patients with hyposplenism?

    <p>To monitor the effectiveness of vaccines</p> Signup and view all the answers

    What is the primary function of antibodies in the elimination of extracellular infections?

    <p>Neutralizing toxins produced by pathogens</p> Signup and view all the answers

    Which cells are primarily responsible for detecting extracellular infections?

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

    How does the innate immune system respond to extracellular infections?

    <p>Through the process of complement activation</p> Signup and view all the answers

    What role do macrophages play in the immune response to extracellular infections?

    <p>Generating cytokines for T cell activation</p> Signup and view all the answers

    What condition is characterized by a reduction or loss of splenic function during an immune response?

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

    Which type of immune response is coordinated between innate and adaptive immunity during extracellular infections?

    <p>Antigen-specific response</p> Signup and view all the answers

    What is the main purpose of phagocytosis in response to extracellular infections?

    <p>To engulf and destroy pathogens</p> Signup and view all the answers

    What types of pathogens are primarily targeted by B cells during an extracellular immune response?

    <p>Extracellular bacteria</p> Signup and view all the answers

    Which of the following conditions may lead to hyposplenism?

    <p>Autoimmune diseases</p> Signup and view all the answers

    Which immune cells are activated following antigen presentation to T helper cells during an extracellular infection?

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

    What is a distinguishing feature of extracellular infections compared to intracellular infections?

    <p>They live and multiply outside of host cells</p> Signup and view all the answers

    What is primarily the role of the complement system in extracellular infections?

    <p>Enhancing phagocytosis and inflammation</p> Signup and view all the answers

    What type of infections require a distinct immune response that involves B cells and antibodies?

    <p>Extracellular bacterial infections</p> Signup and view all the answers

    What is the role of eosinophil granules in combating parasites?

    <p>They contain proteins that are toxic to parasites.</p> Signup and view all the answers

    Which of the following conditions is associated with high levels of IgE and mast cell activity?

    <p>Asthma and allergy.</p> Signup and view all the answers

    Which interleukins are primarily involved in promoting TH2 responses?

    <p>IL-4 and IL-5.</p> Signup and view all the answers

    What kind of infections are TH2 cells particularly adept at combating?

    <p>Extracellular parasitic infections.</p> Signup and view all the answers

    What is the role of Th2 cells in the immune response?

    <p>They facilitate isotype switching towards IgE and IgG.</p> Signup and view all the answers

    Which cytokine is crucial for instructing T cell differentiation towards the Th2 subset?

    <p>IL-4</p> Signup and view all the answers

    What is the function of mast cell granules in response to helminth infections?

    <p>They contain proteases and substances that directly kill the worm.</p> Signup and view all the answers

    What initiates inflammation in the innate immune response?

    <p>Release of secretory antigens like IL-1 and TNF</p> Signup and view all the answers

    Which of the following statements about IgE is true?

    <p>It is involved in the immune response to helminths.</p> Signup and view all the answers

    Which pathogens are recognized as extracellular pathogens by innate immune cells?

    <p>Bacteria, viruses, and fungi</p> Signup and view all the answers

    What is a significant consequence of histamine secretion during immune responses?

    <p>It promotes increased mucus secretion and peristalsis.</p> Signup and view all the answers

    Which of the following is an example of a helminth infection?

    <p>Ascaris lumbricoides</p> Signup and view all the answers

    What should individuals at risk due to hyposplenism carry or wear for identification?

    <p>A splenectomy card or medic-alert bracelet</p> Signup and view all the answers

    What is the primary role of PRRs (pattern recognition receptors) in the immune response?

    <p>To recognize pathogen-associated molecular patterns (PAMPs)</p> Signup and view all the answers

    What activates the classical pathway of complement activation?

    <p>Antibody recognition</p> Signup and view all the answers

    What initiates phagocytosis during an immune response?

    <p>Mannose receptors and complement receptors</p> Signup and view all the answers

    Which cytokines mediate inflammation during an immune response?

    <p>IL-1, TNF, and IL-6</p> Signup and view all the answers

    What is a characteristic feature of Streptococcus bacteria?

    <p>They are gram-positive and encapsulated</p> Signup and view all the answers

    Which condition is commonly associated with Streptococcus infections?

    <p>Pharyngitis (strep throat)</p> Signup and view all the answers

    What type of immune cell is primarily involved in the recruitment process during inflammation?

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

    What instructs T cells in their differentiation during an immune response?

    <p>Antigen presenting cells</p> Signup and view all the answers

    Which immune response is particularly important against extracellular bacterial infections?

    <p>Humoral immunity</p> Signup and view all the answers

    What role do TH17 cells play in the immune response?

    <p>They recruit neutrophils and enhance barrier integrity</p> Signup and view all the answers

    What triggers the production of inflammatory mediators during an immune response to streptococci?

    <p>TLR activation</p> Signup and view all the answers

    Which type of infection primarily relies on the activation of innate immune cells?

    <p>Extracellular bacterial infections</p> Signup and view all the answers

    What is a common result of macrophage activation during inflammation?

    <p>Increased production of reactive oxygen species</p> Signup and view all the answers

    What is the primary immune response immediate upon detection of an extracellular infection?

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

    Which statement best describes the role of the immune response to extracellular bacteria?

    <p>It requires a coordinated response between innate and adaptive immunity.</p> Signup and view all the answers

    What is the main outcome of isotype switching in response to protein antigens?

    <p>Production of IgG and IgA antibodies for enhanced protection</p> Signup and view all the answers

    In the context of antibody production, what is a characteristic feature of the response to toxins?

    <p>Minimal isotype switching resulting in mainly IgM</p> Signup and view all the answers

    What is the significance of long-lived plasma cells generated from a response to protein antigens?

    <p>They provide ongoing antibody production over time</p> Signup and view all the answers

    Which cytokine is associated with producing a Th17 response?

    <p>IL-17</p> Signup and view all the answers

    What is a correct statement about memory B cells generated during the immune response to protein antigens?

    <p>They reside in the bone marrow and gut.</p> Signup and view all the answers

    Which of the following is true regarding the antibody response to Streptococcus pyogenes?

    <p>Antibodies counteract both the bacteria and its exotoxins.</p> Signup and view all the answers

    What is the function of complement activation in the immune response?

    <p>It aids in opsonization and promotes inflammation.</p> Signup and view all the answers

    In terms of antibody longevity and affinity, how do antibodies from short-lived plasma cells differ from those produced in response to protein antigens?

    <p>Antibodies from short-lived plasma cells are generally lower affinity and short-lived.</p> Signup and view all the answers

    What is the role of eosinophil granules in combating parasitic infections?

    <p>They contain proteins that can kill parasites.</p> Signup and view all the answers

    Which interleukins are primarily associated with promoting TH2 responses?

    <p>IL-4 and IL-5</p> Signup and view all the answers

    What immunological structure is indicated by high levels of IgE and mast cell activity?

    <p>TH2 associated diseases</p> Signup and view all the answers

    How does mast cell activity contribute to the immune response against infections?

    <p>By recruiting eosinophils to the site of infection.</p> Signup and view all the answers

    What consequence can result from high levels of IgE antibodies in the body?

    <p>Heightened allergic responses and asthma.</p> Signup and view all the answers

    What is a potential consequence of reduced splenic function related to antibody production?

    <p>Decreased production of IgM antibodies</p> Signup and view all the answers

    What is a recommended management strategy for patients with hyposplenism?

    <p>Prophylactic antibiotics from birth</p> Signup and view all the answers

    Which of the following conditions is associated with functional hyposplenism?

    <p>Celiac disease</p> Signup and view all the answers

    Which vaccine should be administered as early as possible to patients at risk of infection due to hyposplenism?

    <p>Meningitis C vaccine</p> Signup and view all the answers

    What is a common trigger for patients to experience hyposplenism?

    <p>Surgical removal of the spleen</p> Signup and view all the answers

    In what aspect does the spleen play a role in immune responses?

    <p>Finalization of B cell development</p> Signup and view all the answers

    What is an essential component of preventive care in patients with a congenital absence of spleen?

    <p>Annual measurement of antibody levels</p> Signup and view all the answers

    What type of antibody do short-lived plasma cells produce after spleen development?

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

    Which feature is primarily associated with the Th2 immune response against helminth infections?

    <p>Isotype switching towards IgE</p> Signup and view all the answers

    What is the primary function of IL-4 in relation to T helper cells?

    <p>Inducing differentiation towards Th2 cells</p> Signup and view all the answers

    What is a key role of mast cells in the immune response against helminths?

    <p>Containing granules that release proteases</p> Signup and view all the answers

    Which of the following is NOT a consequence of mast cell activation during helminth infections?

    <p>Suppression of eosinophil activity</p> Signup and view all the answers

    What induces the secretion of inflammatory cytokines such as IL-1, TNF, and IL-8 during innate immunity?

    <p>Release of secretory antigens</p> Signup and view all the answers

    Which interleukin specifically instructs T cell differentiation into the Th2 subset?

    <p>IL-4</p> Signup and view all the answers

    What type of receptors do pathogens interact with to activate the innate immune response?

    <p>Pathogen recognition receptors (PRRs)</p> Signup and view all the answers

    In cases of splenic dysfunction, which precaution should individuals take when traveling?

    <p>Carry a splenectomy card or wear a Medic-Alert bracelet</p> Signup and view all the answers

    What impact does IL-5 have in the immune response against helminths?

    <p>Enhances eosinophil activity</p> Signup and view all the answers

    Which cytokine is primarily responsible for inflammation initiation in the innate immune response?

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

    What distinguishes extracellular bacteria from intracellular bacteria?

    <p>Extracellular bacteria multiply outside of host cells.</p> Signup and view all the answers

    Which component of the immune system plays a major role in both detecting and responding to extracellular infections?

    <p>Innate immune cells and antibodies</p> Signup and view all the answers

    How do antibodies assist in the elimination of extracellular infections?

    <p>By neutralizing toxins produced by pathogens</p> Signup and view all the answers

    Which condition is characterized by reduced or absent splenic function affecting susceptibility to infections?

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

    Which immune response mechanisms are primarily utilized during innate immunity to combat extracellular infections?

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

    What role do macrophages and dendritic cells play in the immune response to extracellular infections?

    <p>They act as the first line of defense.</p> Signup and view all the answers

    Which cytokines are primarily produced by macrophages to mediate inflammatory responses?

    <p>IL-1 and IL-6</p> Signup and view all the answers

    What describes the primary function of phagocytosis in the context of extracellular infections?

    <p>Engulfing and destroying pathogens</p> Signup and view all the answers

    What is the role of complement activation in the immune response to extracellular infections?

    <p>To enhance phagocytosis and induce inflammation</p> Signup and view all the answers

    Which class of infections primarily elicits a TH2 immune response?

    <p>Fungi and helminths</p> Signup and view all the answers

    How is B cell memory established following an extracellular infection?

    <p>Through antibody production and memory cell formation</p> Signup and view all the answers

    Which of the following is a common consequence of hyposplenism?

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

    What type of immune responses are involved when cooperating between innate and adaptive immunity during extracellular infections?

    <p>A mix of cellular and antibody-mediated responses</p> Signup and view all the answers

    What initiates phagocytosis in the immune response?

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

    What is the primary mechanism for killing microbes within the phagolysosome?

    <p>Reactive oxygen species and nitric oxide</p> Signup and view all the answers

    Which pathway is activated by peptidoglycans in bacterial cell walls?

    <p>Alternative pathway</p> Signup and view all the answers

    Which cytokine serves as an instructive mediator during T cell differentiation to the Th17 subset?

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

    What is a major inflammatory mediator produced during innate immune cell activation?

    <p>IL-8</p> Signup and view all the answers

    Which medical condition is most commonly associated with Streptococcus infections?

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

    Which type of immune cells play a key role in the process of antigen presentation to CD4+ T helper cells?

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

    What type of bacteria is specifically characterized as gram positive and aerobic?

    <p>Streptococcus pneumoniae</p> Signup and view all the answers

    Which factor is associated with the release of inflammatory cytokines during the innate immune response?

    <p>Pathogen-associated molecular patterns</p> Signup and view all the answers

    What is the primary purpose of the complement activation in the immune response?

    <p>To facilitate phagocytosis and lyse pathogens</p> Signup and view all the answers

    During which immune response do TH2 cells primarily exert their function?

    <p>Response to parasitic infections</p> Signup and view all the answers

    Which type of receptor is primarily associated with the recognition of pathogens by the innate immune system?

    <p>Pattern recognition receptors</p> Signup and view all the answers

    What specific function does IL-17, produced by TH17 cells, serve in an immune response?

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

    Study Notes

    Responses to Extracellular Infection

    • Module: BMF
    • Year: 1
    • Topic: Responses to extracellular infection
    • Presentation date: November 2024
    • Presenter: Dr. Patrick Walsh

    Immunology Lecture Outline

    • Barrier Immunity:
      • Physical barrier (intro to immune system)
      • Mechanical barrier (intro to immune system)
      • Chemical barrier (intro to immune system)
    • Innate Immunity:
      • Cytokines (intro to immune system)
      • Inflammation (innate immune system lecture)
      • Complement (innate immune system lecture)
      • Antigen presentation (innate immune system lecture)
    • Adaptive Immunity:
      • Response to extracellular infections (immune response to specific types of infection)
      • Cytotoxic and Helper T cells (T cell lecture)
      • Response to intracellular infections (immune response to specific types of infection)
      • B cells, antibodies (B cell lecture)

    Lecture Learning Outcomes

    • Describe the immune response to extracellular infections using streptococci and helminths as examples
    • Explain how innate immune cells detect extracellular infections
    • Describe how antibodies eliminate extracellular infections
    • Explain B cell memory establishment
    • Outline conditions causing hyposplenism
    • Describe the clinical consequences and management of hyposplenism

    Types of Infection

    • Viruses
    • Extracellular bacteria
    • Intracellular bacteria
    • Fungi
    • Protozoan
    • Multicellular parasites

    Extracellular vs. Intracellular Infections

    • Extracellular: Bacteria, Fungi, Protozoa, Helminths, live and multiply outside of cells.
    • Intracellular: Organisms invade a cell for survival, multiplication, and evade detection. (Listeria monocytogenes, Mycobacterium tuberculosis, Viruses)

    Cooperation Between Innate and Adaptive Immunity

    • Macrophages and dendritic cells are the crucial cells that detect and combat infection
    • Existing circulating antibodies specific for surface proteins or lipids of the invading organisms play a role in stimulating T cells and antibody production
    • Presentation of antigens to these cells activates them

    Innate Immunity to Extracellular Infections

    • Complement activation
    • Phagocytosis
    • Inflammatory response

    Complement Activation

    • Classical pathway: Activated by antibodies recognizing antigens from previous infection
    • Alternative pathway: Activated by peptidoglycans in cell walls of gram positive and gram negative bacteria
    • Lectin pathway: Activated by bacteria that express mannose on their surface.

    Phagocytosis and Inflammation

    • Phagocytosis is initiated by mannose and complement receptors.
    • Killing of microbes occurs in phagolysosomes via reactive oxygen species (ROS) and nitric oxide (NO).
    • Production of inflammatory mediators (TNF, IL-1, IL-6, IL-8, prostaglandins)

    Adaptive Immunity to Extracellular Microbes

    • T Helper Cells
    • Antibody production (B cells)

    Summary of Extracellular Bacterial Infection

    • The video is available in the Moodle folder.

    Immune Response to Streptococci

    • Gram positive aerobic bacteria
    • Spherical
    • Encapsulated
    • Polysaccharide rich coat
    • Releases toxins
    • Strains include Streptococcus pyogenes and Streptococcus pneumoniae

    Medical Conditions of Streptococci

    • Pharyngitis (strep throat)
    • Skin Infections (Impetigo, Scarlet fever, Cellulitis)
    • More serious conditions (Toxic shock syndrome, pneumonia, necrotizing fasciitis)

    Overview of Immune Response to Streptococci

    • Extracellular microbe
    • Resident macrophages induce phagocytosis and inflammation
    • Recruitment of neutrophils
    • Antigen presentation to CD4+ T helper cells
    • Antibody production by B cells

    Recognition and Activation of Innate Immunity

    • PAMPs (pathogen-associated molecular patterns)
    • PRRs (pattern recognition receptors)
    • TLRs (toll-like receptors)
    • Cytokines (e.g., IL-1, TNF, IL-8) initially promote inflammation
    • Antigen presentation in lymph nodes

    Th17 Cells

    • Important against extracellular bacteria infections.
    • Functions: Recruitment of neutrophils, release of antimicrobial peptides, and increased barrier integrity
    • Example pathogenic organisms: Streptococcus pyogenes, Streptococcus pneumoniae, Staphylococcus aureus, Candida

    B Cell Response to Streptococci

    • Isotype switching to production of IgG and IgA for mucosal protection.
    • Production of long-lived plasma cells for sustained protection
    • Production of memory B cells

    Antibody Responses

    • Antibodies neutralize bacterial antigens activating complement and promoting phagocytosis
    • Opsonization 'tags' the Streptococcus for recognition and phagocytosis by macrophages

    Follow the Streptococcus (Antigen Recognition and Signaling)

    • TLRs responsible for recognizing Streptococcus surface antigens
    • Signaling is mediated primarily by cytokines (IL-4, IL-5, IL-12, and IL-17)
    • Antibodies may promote opsonization, neutralization, and complement activation.

    Hyposplenism

    • Reduction or loss of splenic function.
    • Causes: Congenital absence of spleen (asplenia), surgical removal of spleen, functional hyposplenism
    • Consequences: Recurrent bacterial infections

    Management of Hyposplenism

    • Prophylactic antibiotics, starting at birth (asplenia) or after splenectomy.
    • Vaccination with polyvalent pneumococcal, Haemophilus influenzae b, and Meningitis C vaccines
    • Annual measurement of antibody titers.
    • Education and awareness of risks for travelers, and bites

    Immune Response to Other Extracellular Pathogens

    • Helminth infections (Schistosoma mansoni, Ascaris lumbricoides, Trichuris trichiura, Necator americanus, and Ancylostoma duodenale)

    Th2 Cells

    • Important against helminth infections
    • Functions: Isotype switching toward IgE and IgG, recruitment of mast cells, eosinophils, mucus production.

    IgE & Eosinophil/Mast Cell-mediated Reactions

    • Mast cell granules contain proteases and other substances directly killing worms
    • Secretion of histamine increasing mucus in gut
    • Eosinophil granules contain proteins toxic for parasite, antibodies help in secondary infections.

    Th2 Associated Diseases

    • Increased susceptibility to asthma and allergies

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    This quiz focuses on the immune response mechanisms to extracellular infections, covering aspects of barrier immunity, innate immunity, and adaptive immunity. Students will explore the roles of cytokines, inflammation, and T and B cells in responding to various infections. Perfect for Year 1 BMF students.

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