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MBIO 1010 > Adaptive Immunity > Flashcards

Adaptive Immunity Flashcards

1
Q

Acquired

A
  • Begins as soon as a pathogen is encountered for the very first time
  • Adaptive response will not occur until a pathogen is encountered
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2
Q

Very Specific

A
  • Very targeted to a specific feature of a given bacterium, virus, toxin
  • Immunity to one pathogen will not confer immunity to another
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3
Q

Has a memory component

A

Produces a more effective response when a pathogen is encountered for the
second time-faster and stronger

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4
Q

Consists of two components

A
  1. Humoral (antibody mediated) immunity
  2. Cell mediated immunity
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5
Q

Antibodies

A

Proteins produced by the immune system that bind and inactivate foreign
antigen

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6
Q

Immunogens

A
  • Any foreign material that has the ability to active the adaptive immune system
    • Normally protein, polysaccharide, lipid material
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7
Q

Epitopes

A
  • The actual portion of the antigen that binds to the antibody
  • A single antigen will have more than one epitope
    • Increases the ability of an antigen to activation the immune system ->
      immunogenicity
    • Each epitope requires a distinct antibody
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8
Q

Hapten

A
  • Low molecular weight compound that is too small on its own to activate
    adaptive immunity
  • Not immunogenic
  • Can bind to other molecules such as protein in blood and tissues
    • Becomes strongly immunogenic
      • An allergy forms
        • Ex) penicillin
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9
Q

Antibody Mediated Immunity

A
  • Antibodies (Ab) are glycosylated protein molecules
    • Also called immunoglobulins (Ig)
    • Consist of 4 subunits
      • Two identical heavy chains
      • Two identical light chains
      • Chains are assembled creating three distinct regions
        • 2 identical variable regions (Fab regions)
          • Provide the specificity of the antibody
        • 1 constant region (Fc region)
          • Allows for interaction with immune cells
          • Based on differences in the Fc region there are five different types of antibody
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10
Q

Classes of Antibody

A
  1. Immunoglobulin M (IgM)
  2. Immunoglobulin G (IgG)
  3. Immunoglobulin A (IgA)
  4. Immunoglobulin D (IgD)
  5. Immunoglobulin E (IgE)
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11
Q

Immunoglobulin M (IgM):

A
  • Pentameric
    • Five different antibody units form IgM
  • Always the first antibody to be produced in
    response to an antigen
    • Primary antibody response
  • Found on the surface of B lymphocytes
    • Remains in the blood
      • Unable to enter the tissues
  • Low affinity for antigen
  • Very good at agglutination
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12
Q

Immunoglobulin G (IgG)

A
  • Monomer
  • Most predominate antibody in the blood
  • Also present in the tissues
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13
Q

Immunoglobulin A (IgA)

A
  • Dimeric
  • Secreted at mucosal sites
    • Saliva, tears, mucous
  • Important defense against respiratory, reproductive, digestive tract infections
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14
Q

Immunoglobulin D (IgD)

A
  • Monomer
  • Located on the surface of B cells
  • Important in activation of B cells to begin producing antibody against a specific antigen
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15
Q

Immunoglobulin E (IgE)

A
  • Monomer
  • Binds to receptors located on the surface of mast cells and basophils
    • Binding of IgE-antigen complex triggers degranulation and histamine release
      • Allergy
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16
Q

Antibody Functions

A
  1. Neutralization
  2. Opsonization
  3. Agglutination
  4. Antibody Mediated cytotoxicity
  5. Complement activation
17
Q

Neutralization

A
  • Antibodies bind to antigen blocking attachment sites
    • Prevents bacteria, virus and toxin entry into tissues and host cells
18
Q

Opsonization

A
  • Antibodies coat the surface of the bacterial cell
    • Attracts phagocytes
    • Greatly enhances the rate of phagocytosis
    • Phagocyte has the ability to interact with the Fc region of the antibody
19
Q

Agglutination

A
  • Each class of antibody can bind to a minimum of 2
    identical antigen units
  • Clumps together many antigens
  • Allows phagocytosis to occur more efficiently
20
Q

Antibody Mediated cytotoxicity

A
  • Attachment of antibody to parasites recruits eosinophils
    • Eosinophils attach to the Fc component of antibodies
    • Activated eosinophil releases reactive oxygen species and hydrolytic enzymes
    • Parasite is destroyed
21
Q

Complement activation

A
  • Complement is a system consisting of a series of proteins found in the blood
    • Can be activated by antibody that is bound to a bacterial cell
      • Classical pathway of complement activation
  • Create a number of different immune responses when activated
    • Memebrane Attack Complex (MAC) attack complex forms
      • Inserts into the membrane of bacterial cell forming a pore
      • Contents of the cell leak and the bacterium dies
22
Q

Activation of Antibody Mediated Immunity

A
  • B cells are antigen presenting cells
    • Macrophages and dendritic cells also perform antigen presentation
    • All antigen presenting cells can insert MHC II into the plasma membrane
  • Antibodies are produced against exogenous antigen
    • Antigen that exists outside of the cell in the surrounding extra-cellular fluid
      • Can be bacteria, virus, parasite, toxin, etc.
    • Once antibodies are secreted from B cells they can bind to and neutralize/opsonize these exogenous antigens
23
Q

What are the Steps in Antibody Production?

A
  1. B cell phagocytoses exogenous antigen
  2. T helper cells bind to MHC II-ANtigen complex resulting in T helper cell activation
  3. Some of these newly produced B cells will become plasma cells
24
Q

B cell phagocytoses exogenous antigen

A
  • Digested content in the phagolysosome will not be exocytosed to the extracellular fluid
    • Instead it will be complexed together with MHC II and inserted into the plasma membrane
25
Q

T helper cells bind to MHC II-ANtigen complex resulting in T helper cell activation

A

The activated T helper cell releases cytokines that bind to receptors on the B cell
resulting in B cell proliferation

26
Q

Some of these newly produced B cells will become plasma cells

A
  • Actively transcribe, translate and secrete an identical antibody protein to the extra- cellular fluid
    - These antibodies are specific to the original exogenous antigen
  • A smaller fraction of newly produced B cells will become memory cells
    • These will be used in subsequent encounters with the same antigen
      • They will not produce antibodies during the current response
27
Q

Primary Antibody Response

A
  • Occurs the very first time a specific antigen is encountered
    • Can be a natural encounter or an artificial encounter (ex: vaccination)
  • Produces a weak antibody mediated response
    • Slow production of low levels of antibody
  • Results in the production of memory B cells: major goal
28
Q

Secondary Antibody Response

A
  • Occurs every additional time (after the primary response) a specific antigen is encountered
  • Produces a strong antibody mediated response
    • Rapid production of high levels of antibody
      • So rapid that the pathogen will not be able to
        establish infection
        • No disease occurs
29
Q

Tolerance

A
  • Tolerance prevents immune responses against self-antigens
    • Any immune cells that are found to recognize self-antigens are destroyed early on in development
    • Helps to prevents auto-immune disease
30
Q

Cell Mediated Immunity

A
  • Recognizes and destroys abnormal cells present in the body
    • Cells infected with virus or obligate intracellular bacteria
    • These are endogenous antigen because they are present inside of the host cell
  • Involves cytotoxic T cells
  • Diseased host cell will display endogenous antigen in the plasma membrane complexed together with MHC I
    • Cytotoxic T cells will bind to MHC I-Antigen complex using their T cell receptor
      (TCR)
    • This results in activation of the cytotoxic T cell
      triggering it to release perforins and granzymes
      that cause death of the infected host cell
  • In order to clear a viral infection both antibody
    mediated immunity and cell mediated immunity are required

MBIO 1010 (13 decks)

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