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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 ... – PowerPoint PPT presentation

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Title: Specific Defenses


1
Specific Defenses
  • The Immune System

2
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

3
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

4
Serum Proteins
Figure 17.2
5
Immunity Types
  • Acquired immunity Developed during an
    individual's lifetime
  • Humoral immunity Involves Ab produced by B
    cells
  • Cell-mediated immunity Involves T cells

6
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

7
Antigenic Determinants
  • Antibodies recognize and react with antigenic
    determinants or epitopes.

Figure 17.3
8
Haptens
Figure 17.4
9
Antibody Structure
Figure 17.5a-c
10
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

11
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

12
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

13
Clonal Selection
Figure 17.8
14
Clonal Selection
  • Bone marrow gives rise to B cells.
  • Mature B cells migrate to lymphoid organs.
  • A mature B cells recognizes epitopes.

15
Self-tolerance
  • Body doesn't make Ab against self
  • Clonal deletion
  • The process of destroying B and T cells that
    react to self antigens

16
The Results of Ag-Ab Binding
Figure 17.9
17
Antibody titer
  • Is the amount of Ab in serum

Figure 17.10
18
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

19
Monoclonal Antibodies
Figure 17.11
20
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

21
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

22
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

23
Dendritic cells present antigens
Figure 17.12
24
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

25
Helper T Cells
Figure 17.13
26
Cell-mediated Cytotoxicity
Figure 17.14
27
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
28
T-independent Antigens
Figure 17.16
29
Antibody-Dependent Cell-Mediated Cytotoxicity
Figure 17.18
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