antigen-antibody interaction lecturer: david. objectives
TRANSCRIPT
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ANTIGEN-A
NTIBODY
INTE
RACTION
L EC
TU
RE
R:
DA
VI D
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OBJECTIVES
• Be able to define an antibody
• Know the major classes of antibodies and their function
• Know what an antigen is and its role in the immune system
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INNATE VERSUS ADAPTIVE RESPONSE
I N N AT E
• First line of defense
• Non-specific
• Ex. Skin
A D A P T I V E
• Cell mediated/Humoral
• Very SPECIFIC and very FAST
• Functions by using ANTIBODIES
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ANTIBODY!
Drag picture to placeholder or click icon to add
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• Heavy Chain• Variable
region• Constant
region
• Light chain• Variable
region• Constant
region
ANTIBODY STRUCTURE
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WHAT IS AN ANTIBODY??
• A protein made in response to a specific antigen.
• It binds an antigen via its variable region
• Secreted by plasma cells
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BUT WHAT IS AN ANTIGEN???
• An antigen is something foreign or toxic that enters the body and causes an immune response. • Ex. Virus, bacteria, toxin made by a bacteria
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SUMMARY
• An antibody binds to an antigen so that an immune response can occur and your body can defend itself.
• The variable region of the antibody binds to the antigen.
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ANTIBODY FUNCTIONS
• There are 4 main functions of antibodies:•Neutralization•Opsonization•Agglutination •Complement
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• Antibody binds bacteria toxin and neutralizes it (makes it harmless)
• After the antigen is neutralized, a white blood cell can bind it and destroys it.
NEUTRALIZATION
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• Binds to an antigen, and targets it for phagocytosis.
• Binding of this antigen to a antibody attracts phagocytes to it.
OPSONIZATION
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• This is activated by interactions between pathogen-antibody-protein
• It allows for rapid amplification of an immune response
• The result of complement is the activation of the membrane attack complex (MAC), which causes lysis of the cell membrane
COMPLEMENT
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AGGLUTINATION
Agglutination is the clumping of particles
It is very important in blood transfusions – ABO blood groups
• There are 4 blood group types• A – has A antigen, body contains anti-B antibodies• B – has B antigen body contains anti-A antibodies• AB – has A and B antigen body, contains neither anti-A nor anti-B antibodies• O – has no antigen, body contains both anti-A and anti-B antibodies
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ABO BLOOD GROUPS
• AB is the universal acceptor
• O is the universal donor
• Why?
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THERE ARE LOTS OF TYPES OF ANTIBODIES• Antibodies are also called
immunoglobulins, or Ig.
• Different classes:• IgG• IgA• IgM• IgE• IgD
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IgG
• Provides the MAJORITY of protection against invaders among the antibodies
• Can cross the PLACENTA
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IgA
• Found in mucosal areas respiratory tract and gut
• Found in tears, saliva, and breast milk
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IgM
• The antibody that first appears when an antigen is found in the body
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IgE
• Binds allergens and releases histamine
• Responsible for ALLERGIES
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IgD• Bind basophils and mast cells• Not much is known
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OBJECTIVES
• Be able to define an antibdy
• Know the major classes of antibodies and their function
• Know what an antigen is and its role in the immune system
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QUESTION
Which immunoglobulin can cross the placenta?
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ANSWER
IgG
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QUESTION
If you mix a person with type A blood and anti-A antibodies, will agglutination occur?
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ANSWER
Yes
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QUESTION
What is the difference between neutralization and opsonization?
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ANSWER
Neutralization – antibody binds a toxin and makes it harmless
Opsonization – antibody binds an antigen and targets it for phagocytosis
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LAB TODAY
• Today you will be simulating the Ouchterlony test.
• This test is performed on an agar plate
• Antigen and antibodies are placed in well and allowed to diffuse.
• If an interaction occurs between an antibody/antigen, then a white line appears.