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Humoral Immune Response
Terry Kotrla, MS,
MT(ASCP)BB
Fall 2006
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Humoral Immunity Results in production of proteins called
immunoglobulins or antibodies.
Body exposed to foreign materialtermed antigen which may beharmful to body: virus, bacteria, etc.
Antigen has bypassed other protectivemechanisms, ie, first and second lineof defense.
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Dynamics of Antibody Production
Primary immune response
Latent period
Gradual rise in antibody production taking
days to weeks
Plateau reached
Antibody level declines
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Dynamics of Antibody Production
Antibody production
Initial antibody produced in IgM
Lasts 10-12 days
Followed by production of IgG
Lasts 4-5 days
Without continued antigenic challengeantibody levels drop off, although IgG
may continue to be produced.
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Secondary Response
Second exposure to SAME antigen.
Memory cells are a beautiful thing.
Recognition of antigen is immediate.
Results in immediate production of
protective antibody, mainly IgG but
may see some IgM
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Humoral Immune Response
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Dynamics of Antibody Production
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Cellular Events
Antigen is processed by T
lymphocytes and macrophages.
Possess special receptors on surface.
Termed antigen presenter cell APC.
Antigen presented to B cell
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Basic Antibody Structure
Two identical heavy chains
Gamma
Delta
Alpha
Mu
Epsilon
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Basic Antibody Structure
Two identical light chains
Kappa OR
Lambda
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Basic Antibody Structure
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Basic Structure of Immunoglobulins
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Papain Cleavage
Breaks disulfide bonds at hinge region
Results in 2 fragment antigen binding
(Fab) fragments.
Contains variable region of antibody
molecule
Variable region is part of antibody
molecule which binds to antigen.
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Papain Cleavage
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Pepsin
Breaks antibody above disulfide bond.
Two F(ab)2 molecules
The rest fragments
Has the ability to bind with antigen and
cause agglutination or precipitation
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Papain and Pepsin Cleavage
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IgG
Most abundant
Single structural unit
Gamma heavy chains
Found intravascularly AND
extravascularly
Coats organisms to enhance
phagocytosis (opsonization)
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IgG
Crosses placenta provides baby with
immunity for first few weeks of infants
life.
Capable of binding complement which
will result in cell lysis
FOUR subclasses IgG1, IgG2, IgG3and IgG4
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IgG
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IgA
Alpha heavy chains
Found in secretions
Produced by lymphoid tissue
Important role in respiratory, urinary
and bowel infections.
15-10% of Ig pool
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Secretory IgA
Exists as TWO basic structural units, a
DIMER
Produced by cells lining the mucous
membranes.
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Secretory IgA
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IgA
Does NOT cross the placenta.
Does NOT bind complement.
Present in LARGE quantities in breast
milk which transfers across gut of
infant.
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IgM
Mu heavy chains
Largest of all Ig PENTAMER
10% of Ig pool Due to large size restricted to intravascular
space.
FIXES COMPLEMENT.
Does NOT cross placenta.
Of greatest importance in primary immuneresponse.
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IgM
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IgE
Epsilon heavy chains
Trace plasma protein
Single structural unit Fc region binds strongly to mast cells.
Mediates release of histamines andheparin>allergic reactions
Increased in allergies and parasiticinfections.
Does NOT fix complement
Does NOT cross the placenta
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IgE
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IgD
Delta heavy chains.
Single structural unit.
Accounts for less than 1% of Ig pool.
Primarily a cell bound Ig found on the surface of Blymphocytes.
Despite studies extending for more than 4 decades,a specific role for serum IgD has not been definedwhile for IgD bound to the membrane of many B
lymphocytes, several functions have beenproposed.
Does NOT cross the placenta.
Does NOT fix complement.
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Cellular Immune Response
Important in defending against: fungi,
parasites, bacteria.
Responsible for hypersensitivity,
transplant rejection, tumor
surveillance.
Thymus derived (T) lymphocytes
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Cell Mediated Reaction
Helper T cells turn on immune
response
Suppressor T cells turn off immune
response
Cytotoxic T cells directly attack antigen
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Cell Mediated Immunity
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Lymphokines
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Summary
http://www.biology.arizona.edu/immunology/tutorials/immunology/page2.html
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http://www.jdaross.cwc.net/humoral_immunity.htm http://academic.brooklyn.cuny.edu/biology/bio4fv/page/aviruses/cellular-immune.html
http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect23.htm