INNATE IMMUNE SYSTEM

• Skin and mucous membranes - first line of defense against microorganism invasion
• Cells and chemicals - provide a second line of defense against microorganism invasion
• Natural killer (NK) cells - release chemicals called perforin and granzymes to degrade target cell contents to kill cancer and virus-infected cells
• Inflammatory response - a nonspecific response that is triggered when body tissues are injured; releases histamine and kinin, which causes phagocytes and WBCs to move into the area
• 4 cardinal signs of acute inflammation:

  • Redness - rubor
  • Heat - calor
  • Pain - dolor
  • Swelling (edema) - tumor
  • Functio laesa - loss of function
• Phagocytes - cells such as neutrophils and macrophages engulf foreign material by phagocytosis
• Antimicrobial proteins - enhances innate defenses by directly attacking microorganisms and hinders their reproduction, with their most important types being complement proteins and interferon
• Complement - a group of at least 20 plasma proteins that activates when they encounter and attach to cells (complement fixation)
• Membrane attack complexes (MACs) - produce holes or pores in cells, a result of complement fixation
• Interferon - small proteins secreted by virus-infected cells to attach on healthy cells to prevent viruses from multiplying
• Fever - increased body temperature due to microorganism invasion to inhibit the release of iron and zinc (needed by bacteria) from the liver and spleen