Chapter 17: Adaptive Immunity Flashcards Preview

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Flashcards in Chapter 17: Adaptive Immunity Deck (42):
1

The ability, obtained during the life of the individual, to produce specific antibodies and T cells

Adaptive Immunity

2

First response to particular antigen called ______ ______.

Primary Response

  • May take a week or more to develop; during this time, the innate immune system is working

3

Immune system remembers pathogen on subsequent exposure

​Secondary Response

4

Adaptive Immunity divided into 2 categories

  1. Humoral immunity
  2. Cellular immunity

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Humoral Immunity

  • Works to eliminate antigens that are extracellular like bacteria, toxins, viruses in the blood or fluid in the tissues
    • extracellular antigens
    • B cells that secrete antibodies

6

Cellular Immunity

  • eliminates antigens residing inside a host cell like a virus which has infected a host cell
    • Intracellular antigen
    • T cells (do no secrete antibodies)

7

​B cells

  • B lymphocytes
  • Develops in bone marrow
  • B cells may be triggered to proliferate into plasma cells
    • Plasma cells produce antibodies
      • antibodies are produced when antigen binds a B cell receptors
  • Some B cells produce  memory cells

8

T Cells

  • T lymphocytes
  • Matures in thymus
  • 2 subsets:
    1. Cytotoxic T cells
    2. Helper T cells
  • T cell receptors also recognize antigen

9

​Antigens

  • Antibody generator
    • coined from compounds that produce antibodies
  • Proteins and polysaccharides induce strong response
  • Recognition of antigen directed at antigenic determinant or epitope

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Epitopes

  • sizes range from 10 amino acids up to larger protrusions
  • multiple epitopes on any macromolecule surface

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​Antibodies

  • a protein produced by the body in response to an antigen, and capable of combining specifically with that antigen
  • antibody = ​immunoglobin (Ig)

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Ab divided into 5 classes

  1. IgG
  2. IgA
  3. IgM
  4. IgD
  5. IgE

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IgM

  • First Ab to respond to infection
  • 5-13% of Ab in circulation
  • Pentamer
  • Primarily exists in blood

14

​IgG

  • Dominant Ab in circulation (80-85%)
  • Monomer
  • Long-half life
  • Able to enter tissues
    • Only Ab that can cross the placenta
      • Maternal IgG protects fetus and newborn
  • The antibody of memory

15

IgA

  • Found in secretions
  • 10-13% of Ab in circulation
  • Dimer in secretions
    • monomer in serum
  • Breast milk, mucous, tears, saliva

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5 Protective Outcomes of Antibody binding to antigen

  1. Agglutination
  2. Opsonization
  3. Neutralization
  4. Activation of Complement
  5. Antibody-dependent cell-mediated cytotoxicity

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Agglutination

  • Reduces number of infectious units to be dealt with (clumping)

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​Opsonization

  • Coating antigen with antibody enhances phagocytosis

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​Neutralization

  • Blocks adhesion of bacteria and viruses to mucosa

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​Activation of complement

  • Causes inflammation and cell lysis

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Antibody-dependent cell-mediated cytotoxicity

  • Antibodies attached to target cell causes destruction by macrophages, eosinophils, and NK cells

22

Antibody production

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​Forms of Lymphocytes

  • Immature
  • Naive
  • Activated
  • Effectors
  • Memory Lymphocytes

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Immature

  • no antigen receptor

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Naive

  • have antigen receptor but have not yet encountered antigen

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Activated

  • have bound antigen, able to proliferate

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Effectors

  • descendants of activated lymphocytes, able to produce specific cytokines
    • examples:
      • Plasma cells
      • T helper cells
      • cytotoxic T cells

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​Memory lymphocytes

  • long-lived descendants of activated lymphocytes
  • memory cells are responsible for the speed and effectiveness of the secondary response
  • remembers antigen on subsequent exposure

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To prevent damaging self, B cell needs a ____ _ __ in order to be activated

  • Helper T cell

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T Lymphocytes

  • Cytotoxic T cells
    • destroy infected or cancerous "self" cells
    • have CD8 marker
    • recognize MHC class I
  • Helper T cells
    • multiply and develop into cells that activate B cells and macrophages
    • stimulate other T cells; orchestrate immune response
    • have CD4 marker
    • Recognize antigen display by MHC class II

31

T lymphocytes cont...

  • never produce antibodies
    • T cell receptor does not react with free antigen
      • Antigen must be presented by Antigen-Presenting Cell (APC) aka B cells and macrophages

32

Major Histocompatibility Complexes (MHC)

  • also called HLA (human leukocyte antigens)
  • Class I MHC on all nucleated cells
  • Class II MHC on APCs
    • ​​B Cells
    • Macrophages
    • Dendritic cells

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Antigen Presentation

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  • Antigen (usually protein molecule) binds to B cell receptor
  • B-cell internalizes the antigen, enclosing it within a membrane-bound vacuole inside the B cell
  • In the vacuole, antigen (protein) is degraded into peptide fragments
  • Peptide fragments are delivered to Major Histocompatibility Complex II molecules that then move to the surface of the cell

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Secondary Response

  • Memory cells responsible secondary response
  • Vaccine exploits phenomenon of immunologic memory
  • Some memory B cells will differentiate into plasma cells

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Cytotoxic T Cell actively destroys the target cell

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Functions of Tc (CD8) cells

  • Induce apoptosis in "self" cells
  • Nucleated cells degrade portion of proteins

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T cell activation

  • Naive T cell to an effector T cell, has to see another (second) signal
  • (signal 2) is provided by the dendritic cell

39

Obtaining Antibody

  • Retrieved by harvesting animal's serum
    • Serum is blood that has red and white blood cells removed and the clotting factors removed
    • All that remains is the fluid portion containing proteins such as antibodies

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40

​Principles of Immunological Testing

  • Seronegative
    • person not yet exposed to antigen and has no specific antibodies
  • Seropositive
    • person with exposure and actively producing antibody
  • Titer
    • concentration of antibody in serum
    • Indicates previous exposure

41

Attenuated Vaccines (long term)

  • Weakened form of pathogen
  • Strain replicates in vaccine recipient

42

Inactivated Vaccine (short term)

  • Unable to replicate in vaccinated individual
  • Retains immunogenicity of infectious agent
  • Inactivated vaccines fall into 2 categories:
    1. Whole Agents
      • contain killed organisms of inactivated virus
    2. Fragments
      • portions of organisms or agents including toxins, proteins, and cell wall components