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1 Immune Defenses Against Disease Chapter 15 (innate immunity) Chapter 16 (adaptive/acquired immunity) Chapter 17 (passive vs active immunization – pp.

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Presentation on theme: "1 Immune Defenses Against Disease Chapter 15 (innate immunity) Chapter 16 (adaptive/acquired immunity) Chapter 17 (passive vs active immunization – pp."— Presentation transcript:

1 1 Immune Defenses Against Disease Chapter 15 (innate immunity) Chapter 16 (adaptive/acquired immunity) Chapter 17 (passive vs active immunization – pp 505-512) Health lies in the balance your immune system achieves in its response to different antigens Response vs Tolerance Modulation of response Immune Defenses

2 2 What are the two main arms of the immune defense system? 1. ‘Innate’ defenses against infection (antigen-nonspecific) ‘Barriers’ to infection Normal microbiota Cellular / enzymatic responses 2. ‘Acquired’ defenses against infection antigen-specific humoral & cell-mediated systems These systems interact in many ways

3 Immune Defenses3 What are the types of Innate Immunity? I. Non-induced mechanisms “Barriers to infection” -- 1 st line of defense Anatomical Mechanical Cilia and mucus Skin wounding

4 Immune Defenses4 Innate Immunity… II. Cellular responses Physiological, e.g., fever Cellular, e.g., phagocytosis Enzymatic, e.g., complement Receptor-mediated Broadly specific -- recognize “danger signals” -- molecules shared by many pathogens “PAMPs” Responses pathogen killing (intra- & extra-cellular) activation of acquired immune responses http://lpi.oregonstate.edu/infocenter/phagocytosis.html

5 Immune Defenses5 What are the cells of the Immune System? Innate granulocytes macrophages Acquired lymphocytes ‘Cytokines’ coordinate activities

6 Immune Defenses6 Organs of the Immune system Primary Lymphoid organs Bone marrow Thymus Secondary lymphoid organs Spleen lymph nodes etc. B-cells and T-cells circulate

7 Immune Defenses7 What are 4 characteristics of the Adaptive Immune system? Specificity Diversity Memory Self/nonself discrimination What are the two branches? Humoral Response: Attack free antigens via antibodies B-cell lymphocytes “B-cell receptors” (BCR) Cell-mediated Response: Hormonal regulation Attack infected cells T-cell lymphocytes “T-cell receptor” (TCR) AG on MHC proteins

8 8 Acquired Immune system recognizes antigens …What is an antigen? Complex macromolecules (e.g., proteins) -- distinctive to a pathogen (+/-) Perceived as “foreign” -- ‘self ‘ vs ‘non-self’ B-cell antigens (antibodies) -- on pathogen surface T-cell antigens -- from intracellular pathogens Immune Defenses

9 9 What is an epitope? Actual part of the antigen recognized By antibody or T-cell Receptor

10 Immune Defenses10 What is an antibody? Functional regions antigen binding sites constant region -- triggers response hinge region What are the 5 types of antibodies and their functions? IgG – primary serum Ig IgA – secretory Ig IgM – B-cell receptor IgE – eukaryotic Ags IgD – membrane associated

11 Immune Defenses11 How does the Humoral System respond to an infection? “Clonal Selection” ‘Naïve’ B-cells Activation (AG selection) + T H cell stimulation Plasma cells “Antibody” factories Memory cells create acquired defense (T-cell response is similar)

12 Immune Defenses12 Clinical Manifestation of Immunity Primary vs Secondary responses Differences in: lag time Ab Titer memory cells

13 Immune Defenses13 How do antibodies trigger an immune response? Blocking of receptors Toxin neutralization Antigen clearing Enhanced phagocytosis Activation of complement

14 14 T-Killer cell activation is carefully regulated “Professional” antigen presenting cells T-Helper cells Tc (T-Killer) cells -- attack infected body cells -- trigger cell death Thus, the need for attenuated pathogen vaccines! Immune Defenses

15 15 How does the Cell-mediated system respond to infections? MHC proteins -- antigen “presentation” Role of macrophages T-Helper cells -- release cytokines -- interferons, interleukins, etc Cytotoxic-T (T-Killer) cells -- attack infected body cels --trigger cell lysis, apoptosis Killer-T cell activationKiller-T cell video

16 How can our bodies produce millions of different types of B-cells and T-cells? Each B- or T-cell can recognize only a specific antigen Antibody/TCR genes are randomly “rearranged” Why don’t B and T-cells act against “self” antigens? -- Cells “tested” in bone marrow and thymus 16Immune Defenses

17 17 How is MHC different? -- 100s of different MHC among humans -- We each possess only 12-18 -- inherited from parents Cause predispositions -- Disease susceptibility -- Allergies -- Autoimmune disorders Is basis of Transplant Compatibility Immune Defenses

18 18 Types of tolerance Central vs Peripheral Types of peripheral tolerance 1. Missing signals, e.g., -- no T H help for B-cells or Tc cells 2. Treg cells -- Immunosuppressive cytokines 3. Tolerogenic DC cells -- induced by missing danger signals

19 Immune Defenses19 Overview of Acquire immune responses Cell meditated T H activated by AG presented on P-APC -- cytokines needed for T C and B-cell activation T C activated by DC cells & AG presented on infected cell -- kill target cells Humoral B-cells activated by free AG Ab bind to pathogens -- induce phagocytosis -- activates “complement” -- etc

20 Immune Defenses20 Immunization Passive Immunotherapy maternal antibodies anti-toxins Active Immunotherapy (i.e., vaccination) Types of vaccines dead cells attenuated cells molecular components Vaccine production

21 Immune Defenses21 Autoimmune disorders Examples Type I diabetes -- B-cells of pancreas Rheumatoid arthritis -- cartilage of joints Myasthenia Gravis -- acetylcholine receptors Multiple sclerosis -- myelin sheath

22 22 How can microbes trigger Autoimmune disorders? Examples Type I diabetes -- B-cells of pancreas Rheumatoid arthritis -- cartilage of joints Myasthenia Gravis-- acetylcholine receptors Multiple sclerosis -- myelin sheath Possible examples of “Molecular Mimicry” Immune Defenses

23 23 What causes Allergies Two steps Sensitization B-cells ----> IgE mast cells Triggering mast cell activation histamine inflammation Immune Defenses IgE and Allergy


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