Immune system


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Immune system

  1. 1. Immune system Basics
  2. 2. Immune system▶ the exogenous microscopic life forms▶ the defective, damaged, malignantly transformed cells = complex set of tissues + mobile elements self/non self discrimination organism protection
  3. 3. Immune cells form the major immune organs circulate through the lymphatic and blood vessels recirculate circulate extravascular spaceModulating leukocyte recruitment in inflammationMargaret Kelly et al.J Allergy and Cl Immunology, 2007
  4. 4. Immune system responses to pathogens Innate immune system Adaptive immune system▶ first line of defense ▶ second line of defense▶ exists before ▶ adaptive – specificexposure to microbes response▶ non-specific immune ▶affords protectionsystem against re-exposure to the same pathogen has cellular and humoral components by which they carry out their protective function
  5. 5. Non-specific Immunity Specific ImmunityResponse is antigen-independent Response is antigen-dependent There is immediate maximal There is a lag time between response exposure and maximal response Not antigen-specific Antigen-specific Exposure results in no Exposure results in immunologic immunologic memory memory
  6. 6. Innate Immune System barriers Defense mechanismsSkin (1st line of defense) sweat – desquamation – flushing – organic acidsNasopharynx mucus – saliva – lysozymeEyes tears – lysozyme - phospholipaseRespiratory system mucociliary elevator – surfactant – defensins (low molecular weight proteins)GI tract peristalsis – gastric acid – bile – digestive enzymes – gut flora
  7. 7. Inflammation one of the first responses stimulated by chemical factors released by injured cells h"p:// Macrophages and mast cells Local inflammatory response: Phagocytic cells release chemical signals such Capillaries widen. Fluid digest pathogens, as Histamine. containing antimicrobial and the tissue proteins enter the tissue. heals. More phagocytes invade the site.Symptoms: redness, heat, swelling, pain and possible dysfunction of the organs or tissues involved
  8. 8. Complement system - a biochemical cascade Alternative pathway Lectin pathway Classical pathway Pathogen surface creates local C-reactive protein or antibody Mannose-binding lectin binds environment conducive to binds to specific antigen on to pathogen surface complement activation pathogen surface First to act Second to act Third to act COMPLEMENT ACTIVATION Cleavage of C3 to C3a and C3b C3b covalently bound to surface components of pathogen Opsonization of pathogens, Recruitment of Perforation of pathogen facilitating uptake and inflammatory cells cell membranes killing by phagocytes Death of pathogen
  9. 9. Cells of the innate immune response Leukocytes: are the products of multipotent hematopoietic stem cells from the bone marrow are able to move freely and interact with and capture cellular debris, foreign particles, or invading microorganisms Include: natural killer cells mast cells eosinophils basophils phagocytes: macrophages,neutrophils, dendritic cellsHierarchies of organization in the innate immune system -
  10. 10. Adaptive (specific) immune system a pathogen that evadesTrigger the innate immune system        an$gen-­‐specific   defense  mechanismsmajor functions ▶ recognition of specific “non-self” antigens ▶ response to eliminate specific pathogens ▶ development of immunological memory
  11. 11. Adaptive (specific) immune system Active immunity Passive immunityis  produced  by  the  person’s  own  immune   the  transfer  of  an:body  produced  by  onesystem  –  highly  adaptable human  or  other  animal  to  anotheris  usually  permanent  (immunologic provides  protec:on  against  some  infec:onsmemory) –  is  temporary
  12. 12. Lymphocytes. A scanning electron micrograph showing lymphocytes (yellow, like cotton candy), red blood cells, and platelets. (Copyright Dennis Kunkel Microscopy, Inc.)Foreign substance (non self)= antigenes (infectious agents X noninfectious substance:pollens, foods, transplant tissue) Specific immune cells Lymphocytes B and T
  13. 13. Lymphoid tissues - Sites of B cells and T cells differentiation Immature lymphocytes migrate through primary lymphoid tissues: bone marrow – for B lymphocytes thymus – for T lymphocytes Mature B and T lymphocytes rich the secondary lymphoid tissues
  14. 14. The peripheral lymphoid organs contain a mix of B and T cells in different stages of differentiation: 1 2 3▶ naive – mature cells ▶ effector cells ▶ memory cells– they didn’t encounter the – they have been – long-lived survivorscognate antigen activated by their of past infections cognate antigen → active in pathogen elimination
  15. 15. Immunogen = a molecule or molecular fragment CAN bind with antibodies or antigen B and T cells receptors induce an immune responseALL Immunogens = AntigensNOT ALL Antigens = Immunogens(ex: urushiol from the ivy poison)
  16. 16. Immunogenicity includes:foreignness to the hostadequate sizesufficient quantity Criteria used in developing vaccines => which must be highly immunogenic to produce protective immune responses against pathogenic microorganisms
  17. 17. Humoral and Cell-Mediated Immunity Humoral immunity deals with infectious agents in the blood and body tissues managed by B-cells (with help from T-cells) Cell-Mediated immunity deals with body cells that have been infected managed by T-cells
  18. 18. Humoral immune system= the antibody-mediated system because of its use of specific immune-system structures called antibodies
  19. 19. Humoral immune systemActivation phase Ingestion (phagocytosis) of foreign matter by macrophages Digest the infectious agent and then display some of its components on their surfaces Cells called helper-T cells - recognize this presentation, activate their immune response, and multiply rapidlyEffector phase Activated helper-T cells use chemical signals to contact B-cells B-cell descendants become either plasma cells or B memory cells The plasma cells manufacture huge quantities of antibodies that will bind to the antigen and prime it for destruction
  20. 20. The Cell-Mediated System killer-T cells recognize components of the foreign matter material on the surfaces of the infected body cells destroy the invaders (primary response) T memory cells secondary response
  21. 21. Secondary Immune Response - Memory
  22. 22. Immunity as an AdaptationThe Human Immune System= important evolutionary adaptation allows humans to better cope with an often hostile environmenta highly favorable adaptation for the humanto protect the human cellular machineryfrom benefiting parasitical organismsinstead of human cells
  23. 23. Disorders of human immunity Immunodeficiency= one or more of the components of the immune system are inactive: Humoral immune deficiency – hypogammaglobulinemia T cell deficiency – acquired immune deficiency syndrome Granulocyte deficiency – granulocytopenia/agranulocytosis Asplenia Complement deficiency
  24. 24. Disorders of human immunity Autoimmunity= overactive immune response the immune system fails to properly distinguish between self and non-self, and attacks part of the body
  25. 25. Disorders of human immunity HypersensitivityOccasionally – inappropriate response of immune system to the presenceof antigen Four different types of hypersensitivity: Type I: Immediate Hypersensitivity Ex: Allergies to penicillin, insect bites,etc Type II: Cytotoxic Hypersensitivity Ex: Pemphigus, Autoimmune hemolytic anemia (AHA), Goodpastures syndrome Type III: Immune Complex Hypersensitivity Ex: Serum sickness Type IV: Delayed Hypersensitivity