Immunology

• What are the two immune systems involved in pathogen recognition?

  The innate and adaptive immune systems
• What are the key differences between innate and adaptive receptors?

  • Innate receptors: Limited number encoded in genome, clonally distributed, recognizes broad groups of pathogens, triggers immediate response.
  • Adaptive receptors: Huge number generated by gene rearrangement, recognizes very specific pathogens, triggers slower response (days to weeks).
• What are Pathogen Associated Molecular Patterns (PAMPs)?

  PAMPs are molecular structures recognized by Pattern Recognition Receptors (PRRs) on innate cells.
• Where can Pattern Recognition Receptors (PRRs) be located?

  On cell surface, endosomal membranes, and in the cytosol.
• What is the focus of the lesson regarding PRRs?

  The focus is on Toll-Like Receptors (TLRs).
• What are the consequences of detecting PAMPs by PRRs?

  • Aids phagocytosis
  • Activates innate cells
  • Promotes inflammatory mediators
• What are Danger Associated Molecular Patterns (DAMPs)?

  DAMPs are host proteins released during cell injury that activate the immune system.
• What is the role of complement in the immune system?

  • Promotes phagocytosis through opsonization
  • Induces inflammatory responses
  • Directly kills pathogens
• What triggers the classical pathway of complement activation?

  The presence of an antibody-antigen complex.
• What triggers the alternative pathway of complement activation?

  Microbial surface structures, such as LPS.
• What triggers the lectin pathway of complement activation?

  Mannose residues on pathogen glycoproteins binding to host lectins.
• What is the common feature of all complement activation pathways?

  The activation of C3 convertase.
• What are C3a and C5a in the context of complement activation?

  They are powerful anaphylatoxins that cause mast cell degranulation and promote vasodilation.
• What role does C5a play in the immune response?

  C5a is a chemotactic factor that causes directed movement of leukocytes.
• How does C3b contribute to phagocytosis?

  C3b attaches to the microbe and is recognized by complement receptor 1 (CR1) on phagocytes.
• What triggers the formation of the membrane attack complex (MAC)?

  C5b triggers the formation of MAC, which can result in lysis of cells.
• What are cytokines?

  Cytokines are soluble proteins produced by various cell types critical for immune responses.
• What are the different actions of cytokines?

  • Autocrine, paracrine, or endocrine actions
  • Proinflammatory (e.g., IL-1, IL-6)
  • Anti-inflammatory (e.g., TGF-β, IL-10)
  • Involved in cell growth and differentiation
  • Involved in chemotaxis (e.g., CCL3, CXCL1)
• What are the characteristics of cytokines?

  • Pleiotropic: More than one effect
  • Redundancy: Several cytokines can have the same effect
  • Synergy: Combined effect greater than individual effects
  • Antagonism: One cytokine inhibits another
• Which cytokines are produced by macrophages and dendritic cells to induce inflammation?

  TNF and IL-1
• What is the role of IL-6 in the immune response?

  IL-6 induces acute phase proteins from the liver and promotes adaptive immune responses.
• What does IL-12 promote in the immune system?

  IL-12 promotes IFN-γ production and Th1 polarization of helper T cells.
• What is the function of Type 1 Interferon (IFN-α, β)?

  Inhibits viral replication and promotes MHC class I expression.
• What is the role of IL-2 produced by helper T cells?

  IL-2 promotes clonal expansion of antigen-stimulated T cells.
• What is the role of IFN-γ produced by Th1 cells?

  Promotes activation of macrophages to better kill intracellular bacteria.
• What does IL-4 do in the immune response?

  IL-4 is a Th2 cytokine that includes class switching to IgE.
• What is the function of IL-5?

  IL-5 activates eosinophils.
• What does IL-17 promote in the immune response?

  IL-17 promotes neutrophil-based inflammation against extracellular pathogens.
• What is the role of anti-inflammatory cytokines like IL-10?

  IL-10 inhibits the production of pro-inflammatory cytokines by dendritic cells.
• What does TGF-β promote in the immune response?

  TGF-β promotes differentiation to Treg and inhibits effector T cell function.
• What is inflammation?

  • Non-specific, localized protective tissue response to injury
  • Aims to eliminate or wall off the cause of injury
  • Promotes tissue repair
  • Denoted by suffix “-itis”
• What are the cardinal signs of inflammation?

  • Redness
  • Heat
  • Swelling
  • Pain
  • Functional impairment
• What are the steps of inflammation?

  1. Detection of pathogens or danger (PAMPs, DAMPs)
  2. Release of mediators causing vascular and cellular responses
  3. Vasodilation and increased vascular permeability
  4. Recruitment of immune cells
  5. Elimination of trigger
  6. Resolution
• What happens during vasodilation in inflammation?

  Vasodilation increases blood flow, causing redness and warmth.
• What is the role of chemokines in neutrophil recruitment?

  Chemokines induce conformational changes in integrins, allowing leukocytes to adhere tightly to endothelial cells.
• What is the sequence of cell recruitment during inflammation?

  Neutrophils are recruited first, followed by monocytes, then lymphocytes.
• What are the systemic manifestations of inflammation?

  Acute phase response, alterations in white blood cell count, fever, sepsis, and septic shock.
• What are the chemical mediators of inflammation responsible for?

  They impact vasodilation, vascular permeability, chemotaxis, fever, pain, and tissue damage.
• What are the learning outcomes for the MBBS course regarding the immune system?

  • Recognize the role of the immune system in defense against foreign matter
  • Distinguish the function of immune cell types
  • Understand the role of immune response in disease prevention
  • Describe the components of the lymphatic system and their role in host defense