Acute inflammation

• What are the main causes of acute inflammation?

  • Infections - eg bacterial, viral, protozoal
  • Allergic/hypersensitivity - eg eczema, drug rash
  • Physical - eg uv light, foreign body
  • Chemical - eg strong acid or alkali
• What are the typical features of inflammation?


  • heat
  • redness
  • swelling
  • pain
  • loss of function
• Describe the vascular phase of acute inflammation 


  First phase to occur

  • Small vessels dilate - arteriole side dilates
  • vascular endothelium cells contract - creating space in between them
  • Venous side - becomes more permeable and therefore more fluid enters the tissue
• Describe the exudative phase of acute inflammation


  Second phase of acute inflammation

  • fluid and proteins leak through the capillary walls
  • Cells - neutrophils - leak through the venules through the endothelial cells - by process of chemotaxis, neutrophils adhere themselves to the cell wall and then squeeze through the cell gap
• What is meant by transudate?


  The process by which fluid passively flows out of vessels when there is a slight imbalance of osmotic pressure and hydrostatic pressure - mostly water and ions
• What is the third phase of acute inflammation and what cells are involved?


  Cellular phase

  • Macrophages
  • neutrophils
  • Mast cells/basophils
• What is the role of macrophages in the cellular phase?


  Tissue damage activates resting macrophages to produce;

  • chemokines and interleukin - 1
  • stimulate adhesion molecules on endothelium and white cells (mainly neutrophils and monocytes)
  • Tumour necrosis factor
  • stimulates vascular permeability

  Macrophages - derived from circulating monocytes - has the role of clearing debris and dead cells through the process of phagocytosis
• What is the role of neutrophil in the cellular phase?


  Migrate into tissues through process of chemotaxis

  • recognise bacteria by;
  • coating of antibody or complement
  • formylmethionine at end of surface protein chains
  • Phagocytose
  • Kill bacteria via lysozyme destroying cell wall and via hydrogen peroxide production - inside granules in the cell

  Neutrophils then go through apoptosis after 8-12 hours so ongoing acute inflammation needs new cells to be attracted in
• What is the role of basophils/mast cells in the cellular phase?


  Activated by;

  • tissue damage
  • complement derived C3a and C5a
  • Antigens interacting with surface IgE on basophils in allergic reaction

  Produce;

  • Histamine - causes vascular dilation and permeability
  • Leukotrienes - induces chemotaxis in other white blood cells
  • Prostaglandins - cause vascular dilation and pain
• What does the coagulation (clotting) pathway result in?


  Production of fibrin
• What is the role of fibrin in healing?


  • Creates a mesh over the area - this is to try to contain the infection and stop it from spreading
• What are some macroscopic appearances of inflammation?


  • Abscess - pus enclosed by fibrin and connective tissue
  • Pus - inflammatory exudate rich in neutrophils, organisms and dead tissue
  • Empyema - pus enclosed in an existing body cavity eg gall bladder, pleura
• What are some microscopic appearances of inflammation?

  • Swollen endothelial cells
  • Presence of neutrophils - cells with bi - nucleic
  • fibrin and haemorrhage

  will likely look the same in any tissue cells
• What are the sub types of acute inflammation?


  The response to acute inflammation will vary depending on the site in the body.

  • Serous - affects areas like the peritoneum
  • Membranous - affects membranes
  • Suppurative/purulent - pus - eg a skin abscess
  • Haemorrhagic - a place that might leak blood - eg the bladder
  • Fibrinous - organs that produce fibrin
  • Catarrhal - lots of mucus production
• What are the potential outcomes of acute inflammation?


  • Resolution - becomes fully healed, no scarring or tissue loss
  • chronic inflammation - turns chronic - could be because the cause hasn't been removed
  • abscess formation - leads to repair
  • Repair - loss of tissue - regeneration is required, likely to lead to scarring
• What are the beneficial effects of acute inflammation?

  • Dilution of toxins
  • Effector cells and antibodies get to the required area
  • Fibrin helps to wall off further spread of infection
  • Antigens get carried to local and regional lymph nodes - this prevents systemic spread and allows antibodies to be made
  • lymphangitis - stimulates the lymph nodes to make antibodies - helps to filter the lymph fluid so reducing likelihood of infection spread
• What are the harmful effects of acute inflammation?


  • Destruction of normal tissues
  • Swelling within a confined space - eg the brain
• What is meant by sepsis?


  Infection with significant organ failure in two or more organs

  • drop in BP
  • drop in oxygen saturation
  • Becoming drowsy
  • affects blood coagulation
  • affects liver and kidney function
• What is the cytokine storm?


  • Harmful effect of acute inflammation
  • whole activation system of inflammatory response was much more than what was needed - harmful as it caused a large pouring out of fluid from cells into the lungs - reduced oxygen exchange levels - ventilation difficult as there isn't enough air space for gaseous exchange
• What are the systemic effects of acute inflammation?


  • Fever - hypothalamus regulates temperature
  • monocyte/macrophage derived TNF and IL-1 cause resetting of temperature control at hypothalamus - make you hotter or colder than you're supposed to be
  • Acute-phase proteins
  • C-reactive protein - assists complement binding to microbes
  • Production of granulocyte colony stimulating factor -
  • increases the production and release of neutrophils from marrow