diseases

• Innate immunity


  The defence mechanisms of plants and most invertebrates that are non-specific and do not create immunological memory
• Adaptive immunity


  The immune response in vertebrates that is modified on each exposure to the pathogen and highly specific to the particular pathogen
• Antigen


  A substance that, upon entering the body, can evoke an immune response
• Immunogen


  An antigen that produces an immune response
• Self-antigen


  Antigens normally present on cells of the body that should not produce an immune response
• Non-self antigen


  Antigens that are not normally present on the body's cells and can produce an immune response
• Self-tolerance


  The lack of response to self-antigens
• Autoimmune disease


  When self-tolerance breaks down and the immune system responds to self-antigens
• Allergen


  A substance that causes an over-reaction to antigens that are not a danger to the body
• Barriers to infection in organisms

  • Physical barriers
  • Chemical barriers
  • Microbiological barriers
• Chemical barriers in plants

  • Saponins
  • Terpenes
  • Alkaloids
  • Phenolics
  • Cyanogenic glycosides
• If all previous defences fail, plants can use cell-mediated defences involving self-destruction of infected cells
• Physical barriers in animals

  • Unbroken skin
  • Mucus-secreting membranes
• Chemical barriers - external in animals

  • Lysozyme enzymes
  • Toxic metabolites (lactic acid, fatty acids)
• Chemical barriers - internal in animals

  • Stomach acid
  • Digestive enzymes
  • Surfactants in lung fluid
• Microbiological barriers in animals


  • Normal flora preventing growth of pathogens
• Innate immune response


  The immediate, non-specific immune response that exists in all animals
• Characteristics of innate immune responses

  • Non-specific
  • Rapid (within hours)
  • Present in all animals
  • Fixed response (do not adapt)
  • Do not lead to immunological memory
• Innate immune responses in plants

  • Chemical response
  • Production of defensive proteins and enzymes
• Cells of the innate immune response in animals

  • Macrophages
  • Neutrophils
  • Monocytes
  • Dendritic cells
• Phagocytes


  Macrophages, neutrophils, monocytes and dendritic cells that engulf pathogens through phagocytosis
• Inflammatory response


  • Accumulation of fluid, plasma proteins and leukocytes
  • Results in heat, pain, swelling, redness and loss of function
  • Often triggered by substances released from damaged cells
• Initiation of inflammatory response

  1. Pathogens breach physical barriers

  2. Injured cells release cytokines attracting neutrophils

  3. Mast cells release histamine increasing vasodilation and permeability

  4. Platelets release clotting factors

  5. Neutrophils migrate and are activated, recruiting macrophages
• Fever


  Increase in body temperature above normal caused by inflammatory cytokines setting a higher regulated temperature set point in the hypothalamus
• Prostaglandins


  Lipid compounds that help control reactions causing pain, fever and healing in inflammation, and mediate increased blood flow and chemical signals
• Physical barriers include skin, mucous membranes, and secretions such as saliva, tears, sweat, urine, and breast milk.
• Chemical defenses include acidic pH levels in stomach and urine, which kill many bacteria and viruses.
• Innate immunity includes physical barriers, chemical defenses, phagocytes, complement proteins, cytokines, interferons, natural killer cells, and inflammation.
• Innate immunity includes physical barriers, such as skin and mucous membranes, that prevent entry by microorganisms.
• Neutrophils are the most abundant type of white blood cell and are essential for the initial immune response to infections.
• The innate immune system is the first line of defense against pathogens.
• Natural killer (NK) cells are a type of lymphocyte that can recognize and kill infected cells or tumor cells.
• Macrophages are a type of white blood cell that engulfs and digests cellular debris, foreign substances, microbes, and cancer cells.
• Chemical defenses involve antimicrobial peptides (AMPs) like defensins, cathelicidin, and beta-defensins found on epithelia surfaces.
• Cellular defenses involve phagocytosis (engulfment) of pathogens by white blood cells called phagocytes.
• Cellular defenses include natural killer (NK) cells, which destroy infected or cancerous cells without prior sensitization, and phagocytes like macrophages, neutrophils, and dendritic cells that ingest and digest foreign particles.
• Phagocytes can be divided into two types based on their ability to move through tissues: mobile phagocytes (neutrophils and eosinophils) and fixed tissue phagocytes (macrophages).
• The innate immune system is non-specific and responds to all microbes similarly, while the adaptive immune system is specific and requires previous exposure to an antigen.
• Antigens are foreign substances recognized by the adaptive immune system.
• Adaptive (acquired) immune system is specific to pathogen and provides long-term protection through memory B and T lymphocytes.