Adaptive Immunity: Specific Defenses of the Host

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Adaptive Immunity Specific Defenses of the Host
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• Innate immunity Defenses against any pathogen.
• Adaptive immunity Specific antibody and
  lymphocyte response to an antigen.

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Historical Development

• Pasteur observed immunity in chickens injected
  with weakened pathogens.
• Von Behring received the Nobel Prize for
  development of antitoxin.
• Ehrlichs work led to the identification of
  antibodies in serum.

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Terminology

• Antigen (Ag) A substance that causes the body to
  produce specific antibodies or sensitized T
  cells.
• Antibody (Ab) Proteins made in response to an
  Ag can combine with that Ag.
• Complement Serum proteins that bind to Ab in an
  AgAb reaction cause cell lysis.

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Dual Nature of Adaptive Immunity

• Adaptive immunity develops during an individuals
  lifetime.

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Dual Nature of Adaptive Immunity

• Humoral immunity involves antibodies produced by
  B cells.
• B cells recognize antigens by antibodies on their
  surfaces.
• humoral

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Dual Nature of Adaptive Immunity

• Cell-mediated immunity involved T cells.
• T cells recognize antigens by TCRs on their
  surfaces.

Cell Mediated
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Terminology

• Serology The study of reactions between
  antibodies and antigens.
• Antiserum The generic term for serum because it
  contains Ab.
• Globulins Serum proteins
• Immunoglobulins Antibodies
• Gamma (?) globulin Serum fraction containing Ab.

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Serum Proteins
Figure 17.17
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Antigenic Determinants

• Antibodies recognize and react with antigenic
  determinants or epitopes on an antigen.

Figure 17.1
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Haptens

• React with antibodies.
• How is this different from an antibody?

Figure 17.2
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Antibody Structure
Figure 17.3ab
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IgG antibodies

• Monomer
• 80 of serum antibodies
• Fix complement
• In blood, lymph, and intestine
• Cross placenta
• Enhance phagocytosis neutralize toxins and
  viruses protects fetus and newborn
• Half-life 23 days

Table 17.1 (1 of 3)
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IgM Antibodies

• Pentamer
• 5-10 of serum antibodies
• Fix complement
• In blood, lymph, and on B cells
• Agglutinates microbes first Ab produced in
  response to infection
• Half-life 5 days

Table 17.1 (2 of 3)
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IgA Antibodies

• Dimer
• 10-15 of serum antibodies
• In secretions
• Mucosal protection
• Half-life 6 days

Table 17.1 (3 of 3)
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IgD Antibodies

• Monomer
• 0.2 of serum antibodies
• In blood, lymph, and on B cells
• On B cells, initiate immune response
• Half-life 3 days

Table 17.1 (1 of 3)
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IgE Antibodies

• Monomer
• 0.002 of serum antibodies
• On mast cells, basophils, and in blood
• Allergic reactions lysis of parasitic worms
• Half-life 2 days

Table 17.1 (1 of 3)
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Activation of B Cells
Figure 17.4
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Clonal Selection
Figure 17.5
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Activation of B Cells

• T-independent antigen
• T-dependent antigen

Figure 17.6
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T-Dependent Antigens

• Activated TH cell secretes cytokines
• TH cell recognizes antigen

Figure 17.18, step 1
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Self-Tolerance

• Body doesn't make Ab against self.
• Clonal deletion
• The process of destroying B and T cells that
  react to self antigens.

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The Diversity of Antibodies

• During embryonic development, regions of V genes
  combine with C genes to produce ? 1015 different
  antibodies.

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AntigenAntibody Binding

• Affinity Strength of bond between Ag and Ag.
• Specificity Ab recognizes a specific epitope.

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The Results of Ag-Ab Binding
Figure 17.7
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• M (microfold) cells over
• Peyers patches which contain
• Antigen-presenting cells and
• T cells

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T Cells

• Helper T Cells (CD4, TH)
• TCRs Recognize antigens and MHC II.
• TH1 Activate cells related to cell-mediated
  immunity (TOLL).
• TH2 Activate B cells to produce eosinophils,
  IgM, and IgE.

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Activation of TH
Figure 17.9
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T Cells

• Cytotoxic T Cells (CD8, TC) activated in
  cytotoxic T lymphocytes.
• CTLs recognize Ag MHC I.
• Induce apoptosis in target cell.

Figure 17.11
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Activation of TC into CTL
Figure 17.10
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T Cells

• Regulatory T Cells (TR)
• Suppress other T cells

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Antigen-Presenting Cells

• Digest antigen
• Ag fragments on APC surface with MHC
• B cells
• Dendritic Cells

Figure 17.12
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Antigen-Presenting Cells

• Activated macrophages Macrophages stimulated by
  ingesting Ag or by cytokines.

APC
Figure 17.13
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Extracellular Killing

• Antibody-dependent cells-mediated cytotoxicity.
• Natural killer cells destroy cells which dont
  express MHC I.

Figure 17.14b
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Extracellular Killing
Figure 17.14a
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Immune System Cells Communicate via Cytokines

• Interleukin-1 Stimulates TH cells.
• Interleukin-2 Activates TH, B, TC, and NK cells.
• Interleukin-8 Attracts phagocytes.
• Interleukin-10 Intereferes with TH1 cell
  activation.
• Interleukin-12 Differentiation of CD4 cells.
• ?-Interferon Increase activity of macrophages.
• Chemokines Cause leukocytes to move to an
  infection.

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Immunological Memory

• Antibody titer is the amount of Ab in serum.

Figure 17.15
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Adaptive Immunity

• Naturally acquired active immunity
• Resulting from infection
• Naturally acquired passive immunity
• Transplacental or via colostrum
• Artificially acquired active immunity
• Injection of Ag (vaccination)
• Artificially acquired passive immunity
• Injection of Ab

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Figure 17.18