week 1 overview of immune system

• Immunology


  The study of the structure and function of the immune system
• Immune responses are beneficial to defend against


  • Pathogens: viruses, bacteria, fungi and parasites
  • Cancerous (neoplastic) cells
• Immune responses can be detrimental when they


  • Reject transplanted tissues
  • Attack our own tissues in autoimmunity
  • Attack harmless targets like pollen or peanuts in allergy
• Cellular immunity


  • Discovered by Ilya Ilyich Mechnikov, who discovered cells that killed bacteria (phagocytes) and proposed that immunity is mediated by cells
• Humoral immunity


  • Discovered by Emil von Behring, Kitasato Shibasaburō and Paul Ehrlich, who discovered factors in blood that neutralised viruses (antibodies) and proposed that immunity is mediated by molecules in the serum
• Definitions of immune mechanisms have shifted


  • Cellular
  • Humoral
  • Innate (Non-specific)
  • Adaptive (Very specific)
• Immune cells responding in a co-ordinated way to control a pathogen/prevent disease
• A healthy immune response requires communication & co-ordination
• Immune communicate by releasing

  • cytokine Immune hormones that activate (or shutdown) specific immune mechanisms
  • leukocytes and other have receptor (thụ thể) on their surface to sense their surroundings (môi trường xung quanh)
• immune Communicate by releasing

  Immune hormones that prompt other cells to move towards the chemokine
• Immune functions


  • Can block replication of microbes
  • Can block infection of our tissues or cells
  • Can engulf and degrade microbe or infected cells (phagoctytosis)
  • Can actively kill microbe or infected cells
• Types of pathogens


  • Viruses
  • Bacteria
  • Fungi
  • Parasites
• Extracellular pathogens


  Appropriate immune response is antibody
• Intracellular pathogens


  Appropriate immune response is CD8 T cells
• Levels of immune defence

  • Physical barriers
  • Innate immune processes
  • Adaptive immune processes
• Innate immunity


  • Rapid (minutes to hours to days), non-specific (activated by germ-line encoded receptors), short-lived (no ongoing responses)
• Adaptive immunity


  • Slow (days to weeks), highly specific (lymphocytes are activated by entirely unique receptors), long-lived (activated cells can persist as "memory" cells and provide ongoing protection)
• All cells in your body have their own basic, innate immune mechanisms
• Leukocytes


  Include any and all white blood cells that are found in your blood or in your tissues and have specialised immune mechanisms
• Leukocyte generation


  1. All leukocytes are generated in the bone marrow

  2. Some undergo further maturation in tissues of the immune system (lymphoid tissues) or while resident in other tissues
• Hematological staining


  Uses chemicals that stain in reproducible ways to identify cell morphology and cell structures that are characteristic of a particular cell type
• Antibody-based staining


  Uses antibodies that are highly specific for a particular protein or other molecule on the surface of the cell to acts as markers of a particular cell type
• Cluster of Differentiation (CD)


  Molecules on the surface of leukocytes that have a CD name and are used as markers of a particular cell type
• Leukocyte subtypes identified by

  • Hematological staining
  • Antibody-based staining
• Granulocyte subtypes


  • Neutrophils
  • Eosinophils
  • Basophils
  • Mast cells
• Neutrophils


  • ~70% of blood leukocytes, short-lived (2-3 days), first leukocyte recruited to the site of inflammation, functions include phagocytosis, releasing cytokines, releasing granules and reactive oxygen species to kill microbes, releasing extracellular traps (nets of DNA) to trap microbes
• Eosinophils


  • ~2% of blood leukocytes, short-lived (Up to 12 days), important for parasite immune responses but also contribute to allergy/asthma, functions include releasing major basic protein to activate basophils and mast cells, enhancing IgE and Th2 responses
• Basophils


  • ~1% of blood leukocytes, short-lived (hours-days), important for parasite immune responses but also contribute to allergy/asthma, functions include releasing histamines and other immune enhancers, enhancing IgE and Th2 responses
• Mast cells


  • Tissue-resident granulocytes, made in bone marrow but mature in tissue, important in parasite and allergic immune responses, functions include releasing histamines and other immune enhancers, enhancing IgE and Th2 responses
• Phagocytes


  Cells that engulf and degrade microbes, can sometimes activate adaptive immune cells by presenting antigens on MHC molecules
• Monocytes


  • ~10% of blood leukocytes, made in bone marrow, spend days in the circulation before migrating to tissues, functions include phagocytosis and triggering inflammation
• Macrophages


  • Monocytes that migrate into tissues can become macrophages and can be long-lived, initiate and regulate innate and adaptive immune responses, functions include phagocytosis
• Mast cells


  Cells that release histamines and other immune enhancers, enhancing IgE and Th2 responses
• Mast cells


  • Very intense, large, dark blue granules
• Phagocytes


  Cells that eat, engulf and degrade microbes, can activate adaptive immune cells by presenting antigens on MHC molecules
• Dendritic cells (DCs)


  • Most potent antigen-presenting cells (APCs)
• Monocytes


  ~10% of blood leukocytes, made in bone marrow, spend days in circulation before migrating to tissues, functions include phagocytosis and triggering inflammation
• Monocytes


  • Large cell with indented or horseshoe shaped nucleus
• Macrophages


  Monocytes that migrate into tissues, initiate and regulate innate and adaptive immune responses, functions include phagocytosis, killing of microbes, anti-tumour activity, secreting cytokines
• Macrophages


  • Different morphology in different tissues