36-50

• What is the definition of immunity?

  Enhanced state of responsiveness to a substance
• What are the general characteristics and types of immunity?

  • Natural (Innate) Immunity:
  • Present from birth
  • Nonspecific
  • Barriers to external insults
  • Acquired Immunity:
  • Expressed after exposure to an antigen
  • Specific
  • Involves specific receptors on lymphocytes
  • Requires macrophages
  • Divided into humoral and cell-mediated immunity
• What type of immunity is present from birth?

  Natural (Innate) Immunity
• What is a characteristic of acquired immunity?

  It is specific and expressed after exposure
• What are the two types of acquired immunity?

  Humoral and Cell-mediated Immunity
• What is the primary function of innate immunity?

  First line of defense against infection
• What are the primary defenses of innate immunity?

  • Physical integrity of skin and mucosa
  • Mucus secretion and flow
  • Lysozyme in secretions
  • Gastric acidity
  • Mucociliary movement
  • Digestive tract peristalsis
  • Urine flow
  • Dermal acidic mantle
  • Unsaturated fatty acids from sebaceous glands
• What is the role of lysozyme in innate immunity?

  It splits bacterial murein
• How does gastric acidity contribute to innate immunity?

  It creates an acidic environment to kill pathogens
• What is the protective role of normal microbial flora?

  They prevent colonization by pathogens
• What are the secondary defenses of innate immunity?

  • Complement System:
  • Activated by bacteria or antigen-antibody complexes
  • Produces chemotactic factors and increases vascular permeability
  • Promotes phagocytosis and kills infectious agents
  • Serum Proteins: Include C-reactive protein, haptoglobin, etc.
  • Fibronectin: A nonspecific opsonin
  • Antiviral Interferons: Block viral replication and activate immune cells
• What initiates the activation of the complement system?

  Bacteria or antigen-antibody complexes
• What is the role of C3b in the complement system?

  It acts as an opsonin for phagocytosis
• What are the two types of interferons?

  Type I and Type II Interferons
• What is the function of Type I Interferons?

  Block viral protein synthesis in neighboring cells
• What are the cellular factors in innate immunity?

  • Natural Killer (NK) Cells: Eliminate virus-infected cells
  • Professional Phagocytes: Include neutrophils and macrophages
  • Neutrophils: Major component of inflammatory response
  • Eosinophils: Defense against parasitic infections
  • Monocytes and Macrophages: Phagocytosis and antigen presentation
  • Dendritic Cells: Antigen presenting cells to T and B cells
• What is the primary role of Natural Killer (NK) cells?

  Eliminate virus-infected or intracellular bacteria
• What is the process of phagocytosis?

  Engulfing and killing microorganisms by phagocytes
• What is the protective role of inflammation?

  • Induces fever to inhibit replication of pathogens
  • Causes vasodilation and increased vascular permeability
  • Attracts immune cells to the site of infection
• What induces fever during inflammation?

  Cytokines released by macrophages
• What is the definition of acquired immunity?

  Expressed after exposure to an antigen
• What are the types of acquired immunity?

  • Humoral Immunity: Mediated by antibodies
  • Cell-Mediated Immunity: Mediated by lymphocytes (T cells)
• What are antigens?

  Substances that stimulate immune response
• What are the general characteristics of antigens?

  • Immunogenicity: Stimulate immune response
  • Specific reactivity: Recognized by antibodies and T cells
  • Foreignness: Recognized as "non-self"
  • Size: Generally at least 10 kilodaltons
  • Epitope: Specific binding site for antibodies
• What are haptens?

  Small molecules that require a carrier to be immunogenic
• What distinguishes T-independent antigens from T-dependent antigens?

  T-independent antigens activate B cells directly
• What is the antigenic structure of bacteria?

  • O Antigen: Part of lipopolysaccharide in Gram-negative bacteria
  • H Antigen: Flagella proteins for motility
  • Capsule: Protects bacteria from phagocytosis
  • M Protein: Major virulence factor of Streptococcus pyogenes
  • Lipoteichoic Acid: Anchors cell wall in Gram-positive bacteria
• What is the structure of antibodies?

  Polypeptide chains linked by disulfide bonds
• What are the characteristics of antibodies?

  • Heterogeneous group of proteins
  • Two identical heavy chains and two light chains
  • Variable and constant domains
  • Hypervariable regions define antigen-binding site
• What determines the class of an antibody?

  Heavy (H) chains
• What is the function of the Fc portion of an antibody?

  Responsible for complement fixation and binding
• What are antibodies primarily found in?

  Gamma globulin fraction of serum
• What type of bonds link the polypeptide chains in antibodies?

  Disulfide bonds
• How many heavy chains do antibodies have?

  Two identical heavy chains
• What determines the class of an antibody?

  Heavy chains
• What are the two classes of light chains in antibodies?

  Kappa and lambda
• What is the function of hypervariable regions in antibodies?

  Define the paratope for antigen binding
• What is the Fc portion of an antibody responsible for?

  Complement fixation and binding to receptors
• How many Fab portions does an antibody have?

  Two Fab portions
• What do activated B cells develop into?

  Memory cells or antibody-producing plasma cells