immunology

• What is the primary function of the immune system?


  It can prevent or limit infection.
• How does the immune system combat abnormal cells?

  It can combat abnormal cells made by the body.
• What is the nature of the immune system?


  It is very complex involving many organs, systems, and cell types.
• What aspect of the immune system is the focus of this material?

  Today we are focusing on how it works correctly and relate this to homeostasis.
• What are the primary lymphoid organs?


  • Bone marrow
  • Thymus
• What are the secondary lymphoid organs?


  • Spleen
  • Waldeyer's ring (lymph nodes and tonsils)
  • Bronchus-associated lymph tissue
  • Mesenteric lymph nodes
  • Peyer's patch
  • Genitourinary lymphoid tissue
  • Lymph nodes
• What is the role of the immune system in distinguishing between self and foreign cells?


  The immune system must be able to differentiate between cells that are part of the person (self cells) and those that are not (foreign cells).

  
• How do immune cells learn to recognize self cells?


  As immune cells develop, they learn to recognize a group of proteins on the plasma membrane of the body's cells (self cells).

  
• What are non-self substances?


  Non-self substances can be invading microorganisms such as bacteria and viruses, toxins, or malignant cells.
• What are the two distinct pathways of the immune system?


  • Innate immunity: Rapid response, non-specific.
  • Adaptive immunity: Slower response, specific to pathogens.
• What is the innate immune system?


  It is present even in single-celled organisms and provides a rapid response to pathogens.
• What is the adaptive immune system?


  It reacts to specific pathogens (antigens) and has a slower response as immune cells need to learn about the pathogen.
• What is Human Leucocyte Antigen (HLA)?


  It is a protein recognized as "self" in humans and is unique for each individual.
• Why is a near match of HLA important for organ transplants?

  A near match is a requirement for a successful organ or tissue transplant.
• What are cytokines and their roles in the immune system?


  • Communication system between immune cells.
  • Small proteins acting as molecular messengers.
  • Roles include stimulating blood cell production, regulating the immune system, and triggering inflammation.

  
• How do cytokines affect the liver?


  Cytokines stimulate the production of acute-phase proteins, raising plasma viscosity, indicated by CRP levels.
• What does a raised CRP level indicate?


  Raised CRP levels indicate infection/inflammation.
• What is the role of the hypothalamus in response to cytokines?


  The hypothalamus responds by increasing body temperature, inhibiting viruses and pathogens from replicating.
• How do cytokines affect the heart during septic shock?


  Cytokines increase nitric oxide levels, which increases cardiac output and vasodilation, leading to decreased blood pressure.
• What are the components of the innate immune system?


  • Physical and biomechanical barriers (skin and membranes)
  • Inflammatory process
  • Cells: Phagocytes, natural killer cells, mast cells, eosinophils
  • Complement system
  • Interferons

  
• What is the role of the skin in the immune system?


  The skin acts as a physical barrier preventing most pathogens from entering.
• What happens if the skin is damaged?


  If damaged, an overwhelming number of bacteria can enter the body.
• What triggers the inflammatory process?


  • Microbes
  • Physical agents (trauma, temperature extremes)
  • Chemical agents (drugs, alcohol, pollutants, antigens)
• What are the characteristics of acute inflammation?


  • Lasts 8-10 days
  • Self-limiting
  • Continues until the threat is eliminated
  • Involves vascular and cellular phases
• What are the characteristics of chronic inflammation?


  • Lasts weeks to months
  • If healing is not reached, leads to granulomatous phase
  • Aims to contain damaged tissue
• What causes heat during acute inflammation?


  Heat is caused by increased blood flow to the damaged area and dilation of arterioles and capillaries.
• What causes swelling during acute inflammation?


  Swelling is caused by inflammatory mediators increasing capillary permeability and plasma proteins moving into tissue spaces.
• What is the role of leucocytes during the cellular phase of inflammation?


  Leucocytes are chemically attracted to the site of injury and engulf pathogens and cellular debris.
• What initiates the synthesis of inflammatory mediators?


  Activated mast cells initiate the synthesis of inflammatory mediators.
• What are the local manifestations of inflammation?


  • Redness (erythema)
  • Heat
  • Oedema
  • Pain
  • Loss/impaired function
  • Exudate
• What causes redness and heat in inflammation?


  Redness and heat are caused by increased blood flow to the area.
• What causes pain during inflammation?


  Pain is caused by increased pressure of extra fluid on nerves and irritation by chemical mediators.
• What is exudate and how does it change during inflammation?


  Exudate is caused by increased vascular permeability and initially is light and watery, thickening and discoloring as inflammation progresses.

  
• What are the systemic manifestations of inflammation?


  • Fever
  • Leucocytosis (increase in white blood cells)
  • Plasma protein synthesis
• What is the benefit of fever during inflammation?


  Fever is normally beneficial as organisms are sensitive to temperature changes.
• What is leucocytosis?


  Leucocytosis is an increase in the number of circulating white blood cells.
• What is the role of phagocytes?


  Phagocytes, including neutrophils and macrophages, engulf and destroy pathogens.
• How are neutrophils formed and how long do they exist?


  Neutrophils are formed in bone marrow and exist for a few short days.
• How do macrophages develop?


  Macrophages form from monocytes, which circulate in the bloodstream for 1-3 days before becoming macrophages.
• What is the role of mast cells in the immune response?


  Mast cells deal with larger pathogens and secrete enzymes to degrade them while promoting inflammation.