Humoral Immune Response
Terry Kotrla, MS,
MT(ASCP)BB
Fall 2006
Humoral Immunity
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Results in production of proteins called
“immunoglobulins” or “antibodies”.
Body exposed to “foreign” material
termed “antigen” which may be
harmful to body: virus, bacteria, etc.
Antigen has bypassed other protective
mechanisms, ie, first and second line
of defense.
Dynamics of Antibody Production
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Primary immune response
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Latent period
Gradual rise in antibody production taking
days to weeks
Plateau reached
Antibody level declines
Dynamics of Antibody Production
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Antibody production
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Initial antibody produced in IgM
Lasts 10-12 days
Followed by production of IgG
Lasts 4-5 days
Without continued antigenic challenge
antibody levels drop off, although IgG
may continue to be produced.
Secondary Response
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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
Humoral Immune Response
Dynamics of Antibody Production
Cellular Events
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Antigen is “processed” by T
lymphocytes and macrophages.
Possess special receptors on surface.
Termed “antigen presenter cell” APC.
Antigen presented to B cell
Basic Antibody Structure
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Two identical heavy chains
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Gamma
Delta
Alpha
Mu
Epsilon
Basic Antibody Structure
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Two identical light chains
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Kappa OR
Lambda
Basic Antibody Structure
Basic Structure of Immunoglobulins
Papain Cleavage
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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.
Papain Cleavage
Pepsin
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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
Papain and Pepsin Cleavage
IgG
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Most abundant
Single structural unit
Gamma heavy chains
Found intravascularly AND
extravascularly
Coats organisms to enhance
phagocytosis (opsonization)
IgG
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Crosses placenta – provides baby with
immunity for first few weeks of infant’s
life.
Capable of binding complement which
will result in cell lysis
FOUR subclasses – IgG1, IgG2, IgG3
and IgG4
IgG
IgA
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Alpha heavy chains
Found in secretions
Produced by lymphoid tissue
Important role in respiratory, urinary
and bowel infections.
15-10% of Ig pool
Secretory IgA
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Exists as TWO basic structural units, a
DIMER
Produced by cells lining the mucous
membranes.
Secretory IgA
IgA
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Does NOT cross the placenta.
Does NOT bind complement.
Present in LARGE quantities in breast
milk which transfers across gut of
infant.
IgM
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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 immune
response.
IgM
IgE
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Epsilon heavy chains
Trace plasma protein
Single structural unit
Fc region binds strongly to mast cells.
Mediates release of histamines and
heparin>allergic reactions
Increased in allergies and parasitic
infections.
Does NOT fix complement
Does NOT cross the placenta
IgE
IgD
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Delta heavy chains.
Single structural unit.
Accounts for less than 1% of Ig pool.
Primarily a cell bound Ig found on the surface of B
lymphocytes.
Despite studies extending for more than 4 decades,
a specific role for serum IgD has not been defined
while for IgD bound to the membrane of many B
lymphocytes, several functions have been
proposed.
Does NOT cross the placenta.
Does NOT fix complement.
Cellular Immune Response
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Important in defending against: fungi,
parasites, bacteria.
Responsible for hypersensitivity,
transplant rejection, tumor
surveillance.
Thymus derived (T) lymphocytes
Cell Mediated Reaction
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Helper T cells – turn on immune
response
Suppressor T cells – turn off immune
response
Cytotoxic T cells directly attack antigen
Cell Mediated Immunity
Lymphokines
Summary
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http://www.biology.arizona.edu/immunology/tutorials/immunology/page2.html
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http://www.jdaross.cwc.net/humoral_immunity.htm
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http://academic.brooklyn.cuny.edu/biology/bio4fv/page/aviruses/cellular-immune.html
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http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect23.htm