MICROPARA CHAPTER 5- INFECTION AND IMMUNITY

• Innate immune response


  The body's first, generalized line of defense against all invaders

  
• Adaptive immune response


  Involves the recognition of traits specific to particular pathogens using a vast array of receptors

  
• Adaptive immune response


  • Responds only after the invader is present
  • It is specific, tailoring each response to act only on a specific type of invader
  • It displays memory, responding better after the first exposure to an invader, even if the second exposure is years later
  • It does not usually attack normal body components, only those substances it recognizes as nonself

  
• Distinguishing properties of adaptive immune response

  • Responds only after the invader is present
  • It is specific, tailoring each response to act only on a specific type of invader
  • It displays memory, responding better after the first exposure to an invader, even if the second exposure is years later
  • It does not usually attack normal body components, only those substances it recognizes as nonself

  
• Humoral immune response


  Production and secretion of antibodies or immunoglobulins against specific antigens

  
• Cell-mediated response


  Occurs when cytotoxic cells defend the body against infection
• Humoral immune response


  1. Macrophages take up antigen and present it to T helper cells

  2. T helper cells bind presented antigen and secrete interleukins

  3. Interleukins activate B cells that have bound the antigen

  4. Activated B cells divide and secrete antibodies

  5. Secreted antibodies bind and help destroy the antigen

  
• The innate immune response is always the first response to an infection
• The innate immune response acts fast
• Characteristics of inflammation

  • Fever (calor)
  • Redness (rubor)
  • Swelling (tumor)
  • Pain (dolor)
  • Loss of function (functio laesae)
• Inflammation can help kill the pathogen (fever produces heat that may kill the bacteria/viruses or make them stop replicating)
• Viruses enter body cells, hijack their organelles, and turn the cell into a virus making-factory. The cell will eventually burst, releasing thousands of viruses to infect new cells.
• Interferon


  A protein produced by cells in response to virus infection that inhibits viral replication
• T cells


  Recognize infected human cells and cancer cells, attack these infected cells, and continue to search for more cells to kill
• Diseases that damage the ability of T cells to function threaten the body's ability to defend itself against infection
• Inflammatory response


  Injured body cells release chemicals called histamines, which begin the inflammatory response
• Mast cells


  Release histamine, which signals inflammation
• Histamine


  Causes fluids to collect around an injury to dilute toxins, leading to swelling
• Fever is a defense mechanism that can destroy many types of microbes and helps fight viral infections by increasing interferon production
• While high fevers can be dangerous, some doctors recommend letting low fevers run their course without taking aspirin or ibuprofen
• The best way to treat a cut in your skin is to wash it and cover it with a clean bandage

  
• If an invader gets past the first line of defense, the cells, molecules, and organs of the immune system develop specifically tailored defenses against the invader
• The immune system can call upon these defenses whenever this particular invader attacks again in the future
• Humoral immune responses


  • Resist invaders that act outside of cells, such as bacteria and toxins (poisonous substances produced by living organisms)
  • Can also prevent viruses from entering cells

  
• Humoral immune response


  1. Macrophages take up antigen and attach it to class II MHC molecules

  2. T helper cells bind presented antigen, stimulating them to divide and secrete interleukins

  3. Interleukins activate B lymphocytes that have also bound the antigen

  4. Activated B cells divide and secrete antibodies

  5. Secreted antibodies bind the antigen and help destroy it

  
• Cell Mediated Response


  • Occurs when cytotoxic cells defend the body against infection
  • Involves the development of B and T cells, memory cells and plasma cells

  
• Cell-mediated immune response


  1. Helper T cells are required, so some of the antigen must be taken up by macrophages and presented to helper T cells

  2. Helper T cells bind the presented antigen and become activated to divide and secrete interleukins

  3. Interleukins activate any killer T cells that have already bound antigen attached to class I MHC molecules on infected cells

  4. Activated killer T cells can then kill any cells displaying antigen attached to class I MHC molecules

  
• Helper T-cells


  • Have receptors for recognizing antigens
  • If presented with an antigen, they release cytokines to stimulate B-cell division
  • The key cell to signal an immune response

  
• 1. cells


  • Produce antibodies
  • Antibodies that bind with the invader's antigen are stimulated to reproduce rapidly
  • Differentiate into either plasma cells or memory B-cells
  • Plasma cells rapidly produce antibodies
  • Memory cells retain the "memory" of the invader and remain ready to divide rapidly if an invasion occurs again
• Antibodies


  • Bind to the antigens they are specific for
  • May disable some microbes, or cause them to stick together (agglutinate)
  • Tag microbes so that they are quickly recognized by various white blood cells
• "Killer" T Cells


  • Seek out and destroy any antigens in the system
  • Destroy microbes "tagged" by antibodies
  • Can recognize and destroy cancer cells
• Calling a Halt


  1. When the invader is destroyed, the helper T-cell calls a halt to the immune response

  2. Memory T-cells are formed, which can quickly divide and produce cytotoxic T-cells to quickly fight off the invader if it is encountered again in the future
• Without the innate immune response, the adaptive immune response cannot be activated, because the innate immune response gives the rest of the immune system signals that say there is a real threat to the body that must be eliminated

  
• Stopping inflammation is not always a good thing. For example, you need to have a fever to really mount a full-blown response against a pathogen so taking paracetamol when you have a mild fever (below 38.3ºC) for example, may not always be a good thing since you may lose the sterilizing effects of the fever and dampen the danger signals that activate the adaptive immune response. However, it is still best to get medical advice on how to treat disease
• Acute inflammation


  Can be good since it activates the immune response
• Chronic inflammation


  Is bad because it ultimately leads to tissue damage
• Importance of inflammation in the immune response

  • Inflammation is a signal produced by the body in response to a real infection
  • It also sends signals to the adaptive immune response that there is a real danger present and that it has to be eliminated

  
• Five hallmarks of inflammation

  • Fever
  • Redness
  • Swelling
  • Pain
  • Loss Of Function
• Antibody


  A protein produced by our immune system to specifically bind a target, usually parts of pathogens
• Antigen is a substance / part of pathogen that generate an immune response, usually leading to the production of a specific "antibody" for the given target