Notes - Immunology.docx

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University of British Columbia
MICB 202
Tracy Kion

Immunology  immune system – eliminates pathogens  innate – CP LaPD  complement proteins, lysozyme, defensins, phagocytic cells  adaptive  lymphocytes, antibodies, molecules produced by lymphocytes  recognize/respond to specific molecules on pathogens  selectively eliminate pathogens/foreign molecules Levels of Defense  anatomical and physiological barriers  innate (non-specific immunity)  quick standard, simple  eliminate some pathogens  adaptive (specific immunity)  slow, tailor-made  sophisticated, targeted Cells of Immune System  blood  red blood cells (RBCs)  white blood cells (WBCs or leukocytes)  mononuclear leukocytes – T lymphocytes, B lymphocytes, & monocytes  ~30% of WBCs  monocytes → leave blood → tissues or organs = macrophages  ~65% of WBCs  leukocytes = neutrophils = polymorphonuclear leukocyte (PMNs)  nucleus has several lobes  hematopoietc stem cells (hemo = blood; poiesis = formation)  all blood cells arise from bone marrow  differentiate into any different types of blood cells  cytokine - proteins made by cells that affect behavior of other cells  myeloid precursor cells - BE MMMN  produce basophils, eosinophils, macrophages, mast cells, monocytes, & neutrophils  lymphoid precursor cells  produce T lymphocytes (T cells), B lymphocytes (B cells)  dendritic cells & natural killer cells  from hematopoietc stem cells in bone marrow  many types of dendritic cells: from lymphoid precursor cell or myeloid precursor cell  development unclear Location of the Immune System  distributed through body  blood circulatory system, lymphatic circulatory system, & lymphoid organs  lymphoid organs – primary (1°) or secondary (2°) lymphoid organs primary (1°) lymphoid organs  sites where developing lymphocytes mature  commit to particular antigen specificity  bone marrow & thymus secondary (2°) lymphoid organs  lymphocytes encounter foreign molecules or pathogens  place where adaptive immune responses occur  bone marrow, spleen, & lymph nodes bone marrow – center part of long bones in body thymus – flat, bi-lobed organ above heart spleen – located on the left side of abdominal cavity lymph nodes – located throughout the body  B & T cells - from lymphoid precursor cell in bone marrow  lymphoid precursor cell → B cell precursor → matures → B cell in bone marrow  mature B cells leave bone marrow → circulate → blood, lymph, & 2° lymphoid organs  lymphoid precursor cell → T cell precursor → migrate → thymus → matures  mature T cells leave thymus → circulate → blood, lymph, & 2° lymphoid organs  lymphatic system – separate circulatory system  lymph fluid – clear fluid drains from tissues → lymphatic capillaries → lymph nodes  similar to blood, but lacks RBCs  drains to circulatory system via thoracic duct near heart  blood system & lymphatic system connected Anatomical and Physiological Barriers  first line of defense 1. intact skin – physical barrier preventing pathogens entrance into body  breaks in skin – cuts, punctures, abrasions, insect bites – portal of entry 2. mucous membranes – conjunctivae, alimentary, respiratory, & urogenital tracts secrete mucous entrapping microorganisms  cilia (respiratory system) pushes bacteria upward → caught in oral secretions → swallowed 3. normal body temperatures – inhibit growth of many potential pathogens  fever responses 4. low pH of stomach acids – kill most swallowed pathogens 5. tears, saliva, and other secretions contain lysozyme  enzyme degrades peptidoglycan of cell walls  complement proteins in blood bind to bacteria and lyse them 6. defensins – cationic peptids bind to bacteria  disrupt cell walls Innate Immunity  second line of defense  some components act immediately against infection  main functions – opsonization, activation of complement cascades, chemotaxis, phagocytosis, & activation of pro-inflammatory cytokines  success - can prevent infection from establishing  failure – slows down infection until recruitment of adaptive immune response Pattern Recognition Receptors (PRRs) - on surface of macrophages  ID microbe as dangerous → attach opsonic receptors  bind & facilitate phagocytosis Pathogens (Prokaryotes)  Pathogen-Associated Molecular Patterns (PAMPs) - molecular structure 1. are not produced by mul
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