3.5&6 specific & non-specific body defences

• What are the two main types of non-specific defences?

  Physical and chemical defences
• What role do epithelial cells play in non-specific defences?

  They form a physical barrier against infection
• What is a pathogen?

  A bacterium, virus, or organism causing disease
• What do epithelial cells produce to defend against infection?

  Secretions such as enzymes and mucus
• How does mucus help in non-specific defences?

  It traps dirt and germs, preventing entry
• What happens during the inflammatory response?

  Histamine is released, causing vasodilation
• What is the effect of vasodilation during inflammation?

  Increased blood flow and phagocyte accumulation
• What type of cells recognize and destroy pathogens?

  Phagocytes
• What is phagocytosis?

  Engulfing and destroying pathogens by phagocytes
• What do phagocytes release to attract more phagocytes?

  Cytokines
• What are cytokines?

  Protein molecules signaling white blood cells
• What accumulates at an infected site as pus?

  Dead microbes and phagocytes
• What are the two types of lymphocytes?

  B lymphocytes and T lymphocytes
• What do B lymphocytes produce?

  Antibodies against antigens
• What is an allergic reaction?

  Hypersensitive response to harmless substances
• What do T lymphocytes do?

  Destroy infected body cells
• What is apoptosis?

  Programmed cell death
• How do T lymphocytes distinguish between self and non-self antigens?

  By recognizing antigens on cell membranes
• What happens when T lymphocytes fail to regulate the immune system?

  They may attack self-antigens, causing autoimmunity
• What are memory cells?

  Cloned lymphocytes that survive long-term
• What occurs during a secondary exposure to an antigen?

  Memory cells rapidly produce specific lymphocytes
• What is the effect of HIV on T lymphocytes?

  It attacks and destroys them
• What is AIDS?

  A disease caused by HIV leading to immunodeficiency
• What are common symptoms of HIV infection?

  Flu-like symptoms and swollen lymph nodes
• How does the immune system respond to a secondary exposure compared to a primary exposure?

  It produces antibodies more rapidly and in higher concentrations
• What are some severe illnesses that can develop without HIV treatment?

  Tuberculosis and cryptococcal meningitis
• What is released by mast cells at the site of injury or infection?

  Histamine
• What effect does histamine have on blood vessels?

  It causes vasodilation and increased permeability
• What is the result of increased blood flow during inflammation?

  Accumulation of phagocytes and clotting elements
• What are the steps of the inflammatory response?

  • Histamine is released by mast cells
  • Vasodilation occurs
  • Increased capillary permeability
  • Phagocytes accumulate at the infection site
  • Clotting agents promote coagulation
• What type of cells form a physical barrier to infection?

  Epithelial cells
• Name a chemical secretion produced to defend against pathogens.

  Mucus
• What is a pathogen?

  A virus, bacterium, or microbe causing disease
• Which cell type produces histamine?

  Mast cell
• How does histamine aid the immune response?

  By causing accumulation of phagocytes
• What do phagocytes do to pathogens?

  They destroy them by phagocytosis
• What is involved in phagocytosis?

  Engulfing pathogens and destroying them
• What do phagocytes release to attract more phagocytes?

  Cytokines
• What are cytokines?

  Protein molecules that signal white blood cells
• What accumulates at an infected site as pus?

  Dead microbes and phagocytes