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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