Humoral Immune Response
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Transcript Humoral Immune Response
Humoral Immune Response
Terry Kotrla, MS,
MT(ASCP)BB
Fall 2006
Humoral Immunity
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
Primary immune response
Latent period
Gradual rise in antibody production taking
days to weeks
Plateau reached
Antibody level declines
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 challenge
antibody levels drop off, although IgG
may continue to be produced.
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
Humoral Immune Response
Dynamics of Antibody Production
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
Basic Antibody Structure
Two identical heavy chains
Gamma
Delta
Alpha
Mu
Epsilon
Basic Antibody Structure
Two identical light chains
Kappa OR
Lambda
Basic Antibody Structure
Basic Structure of Immunoglobulins
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.
Papain Cleavage
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
Papain and Pepsin Cleavage
IgG
Most abundant
Single structural unit
Gamma heavy chains
Found intravascularly AND
extravascularly
Coats organisms to enhance
phagocytosis (opsonization)
IgG
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
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
Exists as TWO basic structural units, a
DIMER
Produced by cells lining the mucous
membranes.
Secretory IgA
IgA
Does NOT cross the placenta.
Does NOT bind complement.
Present in LARGE quantities in breast
milk which transfers across gut of
infant.
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 immune
response.
IgM
IgE
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
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
Important in defending against: fungi,
parasites, bacteria.
Responsible for hypersensitivity,
transplant rejection, tumor
surveillance.
Thymus derived (T) lymphocytes
Cell Mediated Reaction
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
http://www.biology.arizona.edu/immunology/tutorials/immunology/page2.html
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