CHAPTER 2: IMMUNOLOGY

• Immune Response


  Generated against a potential pathogen
• Innate Immunity


  • First line of defense and is rapidly mobilized at the initial site of infection but lacks immunologic memory
• Cytotoxic T-Cells (CD8+)


  • Act as a sort of bridge; becomes activated and produces molecules that kill the infected cell
• Helper T-Cells (CD4+)


  • Become activated and begin to produce molecules called cytokines that signal to other immune cells
• Components of Innate Immunity

  • Microbial Sensors
  • Complement System
  • Inflammation and Interferons
  • Cellular Components
• Microbial Sensors


  Regulates bacterial phagosome functions in macrophages
• Types of Microbial Sensors

  • TLRs
  • NLRs
  • RIG1-like helicases and MDAS
• TLRs


  • Recognize pathogen-associated molecular patterns
  • TLR 2 - various ligands
  • TLR 3 - double stranded RNA in viral replication
  • TLR 4 - recognizes G(-) lipopolysaccharides
  • TLR 5 - bacterial fagellin
  • TLR 7&8 - single stranded RNA in viral replication
  • TLR 9 - binds bacterial and viral DNA
• NLRs


  Located in the cytoplasm and serve as intracellular sensors for microbial products; activate the nuclear factor kappa light chain
• RIG1-like helicases and MDAS


  Cytoplasmic sensors of viral ssRNA
• Complement System


  Consists of 30 proteins found in the serum or on the membrane of selected cells that interact in a cascade that will culminate in cellular lysis or destruction of pathogen
• Inflammation and Interferons


  Various cells and complement components of innate immunity orchestrate their effects through the production of soluble mediators
• Cytokines


  Leukocytes, such as macrophages, release a variety of cytokines, including IL-1 and TNF-a, and IL-6
• Cellular Components


  • Circulating phagocytic cells increase and can participate in chemotaxis, migration, ingestion, and microbial killing
• Phagocytes: Dendritic Cell


  Activate T-cells in the adaptive immune response
• Types of Hypersensitivity

  • Type I: Immediate Hypersensitivity (Allergy)
  • Type II
  • Type III: Immune Complex Hypersensitivity
  • Type IV: Cell-Mediated (Delayed)
• Type I: Immediate Hypersensitivity (Allergy)


  Manifests itself in tissue reactions occurring within seconds after the antigen combines with specific lgE antibody
• Type II


  Binding of lgG antibodies to cell surface antigens or extracellular matrix molecules
• Type III: Immune Complex Hypersensitivity


  Antibody combines with its specific antigen, immune complexes are formed
• Type IV: Cell-Mediated (Delayed)


  1. cell mediated response; results in T-cell proliferation, release of potent inflammatory cytokines, and activation of macrophages
• Cytokines


  Mediators induce changes in the expression of adhesion molecules expressed on the surface of endothelial cells
• Fever


  Common systemic manifestation of the inflammatory response
• Interferons


  Critical cytokines that play a key role in defense against virus infections and other intracellular organisms, such as Toxoplasma gondii
• Adaptive Immunity


  • Cellular basis of the adaptive immune response; highly specific, has immunologic memory, and can respond rapidly and vigorously to a second antigen exposure
• Regulatory T-Cells


  Does not activate immune response; play a protective role by shutting off the immune response when it is no longer needed
• Natural Killer Cells


  • Make up 10-15% of blood leukocytes; recognize and kill virus-infected cells and tumor cells; play a critical role in antibody-dependent cellular cytotoxicity
• Antibody-mediated


  Recognize the pathogen's antigens bound to the class II MHC molecules on the surface of an antigen-presenting cell
• Phagocytes


  • Monocytes and Macrophage Monocytes
  • Granulocytes
  • Eosiniphils and Basophils
• Monocytes and Macrophage Monocytes


  Small leukocytes that circulate in the blood and mature into macrophages
• Granulocytes

  Neutrophils have a short half-life and are important phagocytic cells that destroy pathogens withing intracellular vesicles
• Eosiniphils and Basophils


  Less abundant and store granules containing enzymes and toxic proteins that can be released upon activation of the cells
• Disease Occurrence


  • Sporadic
  • Endemic
  • Epidemic
  • Pandemic
• Sporadic


  Occurs occasionally
• Endemic


  Present in the population
• Epidemic


  Many people acquire disease in short amount of time
• Pandemic


  Worldwide epidemic
• Disease Duration


  • Acute
  • Chronic
  • Subacute
• Acute


  Develops rapidly, but lasts a short time
• Chronic


  Develops more slowly, and tend to recur for long periods
• Subacute


  Intermediate between acute and chronic