Specific Defenses

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					Specific Defenses
   The Immune System
                    Definitions
   Innate (nonspecific)   Defenses against any pathogen

   Immunity               Specific antibody and lymphocyte
                           response to an antigen

   Antigen (Ag)           A substances that causes the
                           body to produce specific
                           antibodies or sensitized T cells

   Antibody (Ab)          Proteins made in response to an
                           antigen
                Terminology

   Serology           Study of reactions between
                            antibodies and antigens

   Antiserum          Generic term for serum
    because                 it contains Ab

   Globulins          Serum proteins

   Gamma () globulin Serum fraction containing
    Ab
Serum Proteins




                 Figure 17.2
             Immunity Types


   Acquired immunity        Developed during an
                             individual's lifetime

   Humoral immunity         Involves Ab produced
    by                       B cells

   Cell-mediated immunity   Involves T cells
             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
       Antigenic Determinants
   Antibodies recognize and react with antigenic
    determinants or epitopes.




                                              Figure 17.3
Haptens




          Figure 17.4
Antibody Structure




                     Figure 17.5a-c
               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
               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
              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
Clonal Selection




                   Figure 17.8
            Clonal Selection


   Bone marrow gives rise to B cells.
   Mature B cells migrate to lymphoid
    organs.
   A mature B cells recognizes epitopes.
               Self-tolerance

   Body doesn't make Ab against self
   Clonal deletion
       The process of destroying B and T cells
        that react to self antigens
The Results of Ag-Ab
       Binding




                       Figure 17.9
            Antibody titer:
   Is the amount of Ab in serum




                                   Figure 17.10
         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
Monoclonal Antibodies




                        Figure 17.11
       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
       Cell-Mediated Immunity

   Specialized lymphocytes, mostly T cells,
    respond to intracellular Ags
   After differentiating in the thymus, T
    cells migrate to lymphoid tissue
   T cells differentiate into effector T cells
    when stimulated by an Ag
   Some effector T cells become memory
    cells
       Pathogens entering the
         gastrointestinal or
       respiratory tracts pass
              through:
   M (microfold) cells in
   Peyer's patches which contains
   Dendritic cells which are antigen-
    presenting cells and
   T cells
Dendritic cells present antigens




                              Figure 17.12
                       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
Helper T Cells




                 Figure 17.13
Cell-mediated Cytotoxicity




                         Figure 17.14
              Nonspecific Cells
   Activated
    macrophages:
    Macrophages
    stimulated by
    ingesting Ag or by
    cytokines
   Natural killer
    cells: Lymphocytes
    that destroy
    virus-infected
    cells, tumor



                                  Figure 17.15
T-independent Antigens




                         Figure 17.16
Antibody-Dependent Cell-
 Mediated Cytotoxicity




                       Figure 17.18

				
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