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The Immune system

The Immune system. The Immune system is the body’s defense system. Against: Bacteria Viruses Protists Other living invaders Toxins Foreign debris Cancerous cells The immune system is complex Defends against threats known and unknown. Elements of the Immune system.

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The Immune system

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  1. The Immune system

  2. The Immune system is the body’s defense system • Against: • Bacteria • Viruses • Protists • Other living invaders • Toxins • Foreign debris • Cancerous cells • The immune system is complex • Defends against threats known and unknown

  3. Elements of the Immune system • Many lines of defense, for many kinds of threats • Skin • Blood • Thymus • Spleen • Lymphatic system • Mucous membranes • Bone marrow

  4. Innate vs. Adaptive immunity Innate Immunity Adaptive Immunity Mechanisms which fight specific invaders For unknown threats Responsive Requires time to build defense (days) Cannot anticipate threats Remembers previous threats • Non-specific • Defends against known invaders • Skin, lysozyme • Pre-existing • Cannot adapt to changing threats

  5. Humoral vs. Cell-mediated Immunity Cell- Mediated Immunity Humoral immunity Proteins in blood (“humors”) Innate- complement system, clotting factors, cytokines, etc. Adaptive: Antibodies • Live cells kill invaders • Innate: Phagocytic cells (e.g. macrophages, neutrophils) • Adaptive: B lymphocytes and T lymphocytes create specific responses to unique invaders

  6. Blood is a mixture of cells and plasma Human Blood after centrifugation • ~55% Plasma • ~45% Red blood cells • <1% White blood cells and platelets (“buffy coat”)

  7. Blood plasma • Water • Nutrients • Solutes- Na+, Cl-, wastes, CO2, etc. • Contains humoral immune elements • Some innate immunity

  8. All blood cells are part of the hematopoetic stem cell lineage

  9. Hematopoetic stem cells differentiate into all blood cells • Pluripotent- able to become any one of many cell types • Includes T cells, B cells, macrophages, etc.

  10. Red blood cells carry oxygen and CO2 • Lose nucleus in development • Short-lived, no repair • Packed solid with hemoglobin • Membranes designed to maximize surface area • Facilitate gas transfer

  11. Hemoglobin • The oxygen-carrying protein • Heterotetrameric protein • 2 alpha subunits, 2 beta • Each subunit holds a Heme group • Each heme holds an Fe++ ion • Each Fe++ can bind an O2

  12. Hemoglobin binding curve • In areas of High O2 (e.g., lungs)- binds O2 very well (picks up O2) • In areas of Low O2 (e.g., muscles) binds O2 poorly (drops off O2) • Myoglobin binds O2 in muscle & organ tissues

  13. Platelets assist with blood clotting • Recruit plasma protein fibrinogen to a cut • They release clotting factors • Clotting factors convert fibrinogen to fibrin • Fibrin net prevents blood loss

  14. The liquid part of blood is called   • A) water.   • B) plasma.   • C) serum.   • D) extrastitial fluid.   • E) anionic fluid.  

  15. White blood cells come in a great variety of types

  16. Elements of Innate Immunity

  17. Lysozyme- an innate enzymatic defense • Enzyme that cuts bacterial cell walls • Also cuts chitin, a constituent of fungal cell walls and arthropod exoskeleton • Found in mucous, tears, egg whites

  18. Complement- humoral defense against non-specific invaders • A biochemical cascade • Non-specific • Signalling pathway to cause cell lysis • Also Recruitable by adaptive immune system

  19. Interferons are nonspecific anti-viral signalling molecules

  20. Phagocytic white blood cells devour bacteria

  21. Which of the following, produced by virus-infected cells, diffuses to neighboring cells to help them fight a viral infection? • A) lysozyme • B) interferon • C) histamine • D) antigen • E) interleukin-2

  22. The Inflammatory response

  23. Keeping the body safe comes at a cost • Inflammation implicated in heart disease, etc. • Gum inflammation linked to heart attacks

  24. The lymphatic system collects lymph and houses white blood cells in nodes

  25. Adaptive Immunity contains humoral and cell-mediated components

  26. Adaptive Immunity is learned, and has memory

  27. Antibodies- the Key component of humoral adaptive immunity • Two light chains, two heavy chains • Each contains a variable region and a constant region

  28. Antigen- anything which can be bound by an antibody

  29. B Cells- the source of antibodies

  30. Clonal selection musters B-cell defense forces against specific antigens

  31. Adaptive Immunity is learned, and has memory

  32. Immune cells are the only cells with different DNA • VDJ recombination of light and heavy chains generate antibody diversity • Change is permanent • A form of Russian Roulette for the cell • Successful recombination creates a binding antibody- cell survives • Unsuccessful- cell is destroyed • Finding a good cell takes time

  33. Bound antibodies are the mark of death for invaders

  34. Breast milk contains maternal antibodies • Infants have no acquired immunity • Mother’s acquired immunity is transferred to the baby through nursing • Passive immunity • Is not retained by the baby

  35. Vaccination gives the body active immunity • An antigen sample is given to a person • Person’s immune system mounts a response to the antigen • Antigen can be deactivated/destroyed virus particles, etc. • No waiting time for body to develop 2o immune response

  36. Antibodies can be used as therapy • Some growth factors are overactive in certain cancers • Antibody binds to growth factors, or their receptors

  37. Polyclonal Antibodies • From multiple B cells • Bind to different epitopes of an antigen

  38. Monoclonal antibodies • Obtained from a single B cell • Bind to a single epitope • A single B cell is fused to a myeloma cell • Myeloma cells are immortal

  39. Mouse antibodies can be humanized • Constant regions of mouse antibody are gradually replaced with human sequences

  40. Fluorescent antibodies can be used in scientific experiments • Fluorescent molecules can be linked to antibodies • Antibodies show us where proteins exist in vivo

  41. In an ELISA, Horseradish Peroxidase is linked to a 2o antibody

  42. Indirect ELISATo detect the presence of an antibody Primary Antibody Secondary Antibody Wash Block Wash Substrate

  43. Home pregnancy tests utilize antibodies

  44. The transfer of antibodies from breast milk to an infant is an example of __________ immunity. • A) nonspecific • B) passive • C) humoral • D) active • E) cell-mediated

  45. T cells are the primary cell-mediated adaptive immune response

  46. Major HistocompatibilityComplex (MHC or HLA) • MHCI Found on all cells, recognized by TC cells • MHCII Found on B cells and Macrophages recognized by TH cells

  47. When presented with antigen, Helper T cells recruit other immune cells

  48. The basic function of T cells is to identify and destroy invaders in our • A) blood or lymph. • B) interstitial fluid. • C) cells. • D) immune system. • E) brain.

  49. CD4 on the surface of TH cells is the site of HIV binding

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