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Chapter 17: Specific Defense

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Innate vs. Acquired (adaptive) immunity. Acquired = antigen and antibodies ... Activation of complement for lysis, inflammation, opsonization. Complement System ... – PowerPoint PPT presentation

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Title: Chapter 17: Specific Defense


1
Chapter 17Specific Defense
2
Many divisions in the immune system
  • Innate vs. Acquired (adaptive) immunity
  • Acquired antigen and antibodies
  • Cellular vs. Humoral immunity
  • Active vs. passive immunity
  • Natural acquired vs. passively acquired
  • T cells and B cells

3
Acquired Immunity Fig 17.1
4
Humoral vs. Cellular ImmunityDevelop from the
lymphoid precursor
5
Development of T cells and B cells
6
Humoral Immunity
  • Antibody-mediated
  • Antibodies produced by B cells
  • 2nd part of chapter T cells

7
Antigens Fig 17.3
  • Self versus non-self
  • T cells and B cells removed if they recognize
    self proteins
  • Antigens are mostly proteins or polysaccharides
  • Antigenic determinants (epitopes)
  • Each bacterial cell has many different epitopes

8
Hapten Fig 17.4
  • A Hapten is a partial antigen
  • It is too small to stimulate antibody formation
    by itself
  • When combined with a carrier (another protein),
    the hapten carrier can stimulate an immune
    response

9
Antibody Structure Fig 17.5
  • 2 Heavy and 2 Light Chains
  • Joined by disulfide links
  • Variable regions/hypervariable regions at tip of
    Y
  • Constant regions
  • Fc region (stem)- can bind complement

10
Animation of the antibody structure
  • B cells recognize antigen alone, not in
    combination with MHC
  • B cells recognize intact and entire antigen
  • while T cells recognize only a small part of the
    antigen

11
Different classes of antibodies
  • http//www.whfreeman.com/kuby/content/anm/kb06an01
    .htm

12
Immunoglobulin Classes
  • IgG (80) Monomer found in blood, lymph and
    intestine
  • Most abundant antibody found in blood
  • can fix complement, can cross placenta
  • Enhances phagocytosis, neutralizes toxins and
    viruses, and protects fetus (or newborn)
  • IgD (0.2) Monomer found on B-cell surface,
    blood and lymph
  • function unknown
  • IgE (0.002) monomer found bound to mast and
    basophil cells, and in blood
  • Allergic reactions lysis of parasitic worms, and
    attracts IgG, complement and phagocytic cells

13
IgE and allergy
14
Immunoglobin Classes
  • IgM (5-10) pentamer found in blood, lymph, and
    B-cell surface
  • fix complement, stay in blood, and very large
  • First antibodies produced at initial infection
  • Enhance phagocytosis
  • Important in diagnosis
  • Short lived and at initial infection

15
Immunoglobin Classes
  • IgA (10-15) Dimer with secretory component
    found in secretions
  • A monomer when in blood serum
  • Not very abundant in blood, but very abundant in
    secretions
  • complement fixation (alternative pathway)
  • Defense against respiratory infections and infant
    GI infection

16
Clonal Selection Fig 17.8
  • B cell surface receptor recognizes antigen
  • Proliferation same immunological specificity
  • Memory cells long-term immunity
  • Plasma cells secrete antibodies (2000/sec)
  • Why we dont attack our own cells
  • Self tolerance
  • Clonal deletion in embryo (thymus)
  • Dangerous versus Nondangerous (recognition of
    inflammation response)

17
Memory vs. effector or plasma cells
18
Memory
  • Antibody titer
  • Amount of antibody in the serum
  • Primary response after 1st exposure
  • IgM produced first
  • Lower titer than 2nd response
  • Secondary (memory) response after 2nd exposure
  • Years or decades later
  • This time IgG peaks first and most

19
Primary vs. secondary response
20
  • Look at textbook web site, interactive tutorials
    B cells
  • Look at textbook web site, animations humoral
    immunity

21
Antigen-Antibody Binding Triggers Mechanisms to
inactivate antigens
22
Antibody Activities Fig 17.18
  • Antibody dependent cell-mediated cytotoxicity
  • Antibodies coat infecting cell (large parasite
    usually)FC facing out
  • NK (lysing ability), Macrophage, neutrophils, and
    eosinophils have receptors for FC region of
    antibody
  • Secretion of lytic enzymes to destroy parasite

23
Antibody Activities Fig 17.9
  • Neutralization
  • Block attachment
  • Block active sites (or binding sites) of toxins
  • Activation of complement for lysis, inflammation,
    opsonization

24
Complement System
  • Nonspecific response often stimulated by a
    specific response
  • Causes lysis, inflammation, and phagocytosis
  • Can occur by 2 pathways
  • Antibody reaction (classical)
  • Direct interaction of proteins and
    polysaccharides (alternative)
  • Cascade of events
  • Components
  • Classical C1 through C9 proteins
  • Alternative Factor B, D and P

25
Complement System Fig 16.13
  • Classical Pathway

26
Complement System Fig 16.14
  • Alternative Pathway

27
Complement Activation Fig 16.12
  • Inflammation
  • C3a and C5a bind to mast cells, basophils and
    platelets and triggers histamine release
  • Increases permeability of blood vessel and
    increases emigration
  • C5a can also be a strong chemotactic factor
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