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ANTIGEN-A
NTIBODY
INTE
RACTION
L EC
TU
RE
R:
DA
VI D
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
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
ANTIBODY!
Drag picture to placeholder or click icon to add
• Heavy Chain• Variable
region• Constant
region
• Light chain• Variable
region• Constant
region
ANTIBODY STRUCTURE
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
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
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.
ANTIBODY FUNCTIONS
• There are 4 main functions of antibodies:•Neutralization•Opsonization•Agglutination •Complement
• 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
• Binds to an antigen, and targets it for phagocytosis.
• Binding of this antigen to a antibody attracts phagocytes to it.
OPSONIZATION
• 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
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
ABO BLOOD GROUPS
• AB is the universal acceptor
• O is the universal donor
• Why?
THERE ARE LOTS OF TYPES OF ANTIBODIES• Antibodies are also called
immunoglobulins, or Ig.
• Different classes:• IgG• IgA• IgM• IgE• IgD
IgG
• Provides the MAJORITY of protection against invaders among the antibodies
• Can cross the PLACENTA
IgA
• Found in mucosal areas respiratory tract and gut
• Found in tears, saliva, and breast milk
IgM
• The antibody that first appears when an antigen is found in the body
IgE
• Binds allergens and releases histamine
• Responsible for ALLERGIES
IgD• Bind basophils and mast cells• Not much is known
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
QUESTION
Which immunoglobulin can cross the placenta?
ANSWER
IgG
QUESTION
If you mix a person with type A blood and anti-A antibodies, will agglutination occur?
ANSWER
Yes
QUESTION
What is the difference between neutralization and opsonization?
ANSWER
Neutralization – antibody binds a toxin and makes it harmless
Opsonization – antibody binds an antigen and targets it for phagocytosis
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.