antigen-antibody interaction lecturer: david. objectives

ANTIGEN-A

NTIBODY

INTE

RACTION

L EC

TU

RE

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DA

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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

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!

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• 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.