Types of Acquired Immunity

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Ch. 17 Acquired Immunity

• Types of Acquired Immunity
• Antigens and Antibodies
• B cells and Humoral Immunity
• T cells and Cell-mediated Immunity
• Interrelationship of Cell-mediated and Humoral
  Immunity

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Types of Acquired 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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Artificially acquired passive immunity

• Serology
• Antiserum
• Globulins
• Gamma (?) globulin

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Antigens

• Immunogen/antigen a molecule that specifically
  interacts with an antibody or lymphocyte
• Antigenic determinants (epitopes)

Figure 17.3
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Antibody structure
Figure 17.5a-c
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IgG antibodies

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

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IgM antibodies

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

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IgA antibodies

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

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IgD antibodies

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

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IgE antibodies

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

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B cells and Humoral Immunity

• Bone marrow gives rise to B cells.
• Mature B cells migrate to lymph organs.
• Clonal Selection Specific response of mature B
  cells to an antigens epitopes.
• Immature
• Naïve
• Activated
• Effector/ plasma cells
• Memory

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Clonal Selection
Figure 17.8
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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 Results of Ag-Ab Binding
Figure 17.9
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Antibody titer
Figure 17.10
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Monoclonal Antibodies

• Hybridomas are produced by fusing a cancer cell
  with an Ab-secreting plasma cells
• The hybridoma cell culture is immortal and
  produces monoclonal Abs (Mabs)
• Immunotoxins Mabs conjugated with a toxin to
  target cancer cells
• Chimeric Mabs Genetically modified mice that
  produce Ab with a human constant region
• Humanized Mabs Mabs that are mostly human,
  except for mouse antigen-binding

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Monoclonal Antibodies
Figure 17.11
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Cell-mediated immunity

• Chemical messengers of immune cells
• T -lymphocytes
• T cell receptor
• Helper T cells (CD4)
• Cytotoxic T cells (CD8)
• Delayed hypersensitivity T cells
• Suppressor T cells
• Activation of T cells

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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-12 Differentiation of CD4 cells
• ?-Interferon Increase activity of macrophages
• Chemokines Cause leukocytes to move to an
  infection

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T cell receptor

• Alpha and beta polypeptide chains
• Antigen - major histocompatibility (MHC) binding
  site

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Major Histocompatibility Complex (MHC)

• Class I MHC proteins
• Expressed on every nucleated cell in body
• Class I MHC/peptide antigen bind to TC cells
• Class II MHC proteins
• Expressed only on specific antigen-presenting
  cells (APCs)
• Class II MHC/peptide antigen bind to TH cells

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T Cells

• Helper T Cells (CD4, TH)
• TH1 Activate cells related to cell-mediated
  immunity
• TH2 Activate B cells to produce eosinophils,
  IgM, and IgE
• Cytotoxic T Cells (CD8, TC)
• Destroy target cells with perforin
• Induces apoptosis

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T Cells

• Delayed Hypersensitivity T Cells (TD)
• Associated with allergic reaction, transplant
  rejection, and tuberculin skin test
• Suppressor T cells (TS)
• Turn off immune response when Ag no longer present

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Helper T Cells
Figure 17.13
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Cytotoxic T Cell
Figure 17.14
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Activation of T cells

• Dendritic cells
• Activated macrophages
• Macrophages stimulated by ingesting Ag or by
  cytokines
• Natural killer cells
• Lymphocytes that destroy virus-infected cells,
  tumor

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Cell-mediated and Humoral Immunity

• T-dependent Antigens
• T-independent Antigens
• Antibody-Dependent Cell-Mediated Cytotoxicity
  (ADCC)

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T-dependent Antigens

• Ag ingested and digested by APC
• TH cell specific to Ag reacts with MHC-Ag Complex
• TH cell produces IL-2 to activate B cell
• B cell differentiates into plasma cell that
  secretes Ab

Figure 17.16
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T-independent Antigens
Polysaccharide Ag with multiple repeating
subunits trigger B cell response
B cell
Figure 17.17
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Antibody-Dependent Cell-Mediated Cytotoxicity
Figure 17.18
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Cell-mediated and Humoral Immunity
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Summary of immune system