Immune System

• Diapedesis


  Passage of leukocytes through an unruptured blood vessel wall during inflammation
• Lymphocytes

  • NK cells (innate)
  • B cells (adaptive)
  • T cells (adaptive)
• NK cells

  • Secrete perforin and granzymes to stimulate apoptosis
• Monocytes

  Immature in the blood vessels, but mature into macrophages when entering infected tissue
• Macrophages

  Act as antigen presenting cells to become phagocytes
• Dendritic cells

  Part of the innate immune system, but act as antigen presenting cells to activate the adaptive immune system
• Interferons


  Secreted when cells are infected by a virus, bind to infected cells to warn and prepare for an attack, activate dendritic cells
• Complement system


  • Causes opsonization, histamine release, and activates the MAC
• Opsonization


  Tags the surface of invaders to make them more prone to phagocytosis
• MHC Class I

  On all nucleated cells, activate CD8 T cells
• MHC Class II

  On all anucleated cells, activate CD4 T Cells, which release interleukins to ramp up the immune response
• B cells

  Differentiate into plasma B cells or memory B cells, plasma B cells release antibodies
• Classes of antibodies

  • IgM: largest, first response, pentamer
  • IgA: abundant in secretions, dimer
  • IgE: on basophils and mast cells, monomer
  • IgG: most abundant, crosses placenta to give fetus passive immunity, monomer
  • IgD
• MHC class I cells function by presenting intracellular antigens for self-recognition
• MHC Class II molecules present extracellular antigens to display foreign antigens to the adaptive immune system
• Histamine increases blood flow by dilating capillaries, and increases tissue swelling
• Heparin inhibits blood clotting by inhibiting thrombin