Antigens and MHC
Prof. Dr Shahina Yasmin
, Antigens
Antigen: Molecules which react/bind with antibody,
( product of immune response)
Immunogen: Molecules which induce an immune response
• Any foreign or endogenous substance that elicits an
immune response when introduced into tissues/
susceptible animal.
• All immunogens are antigens, all antigens are not
immunogens
Haptens: small univalent molecules which can react with
specific antibody but not immunogenic.
• These combine with carrier proteins to be immunogenic.
Able to cross link with antibodies eg. penicillin, poison ivy.
• can not bind with MHC Class II molecules but bind with
carrier protein.
, Antigens
• Antigen antibody reaction is highly specific. Lock and key
model
• Antigen and antibody bind with weak forces such as
hydrogen bonds and Vander Waals forces.
• Affinity (strength of binding) depends upon the fit of
antigen at binding site and ability to form more bonds.
Affinity increases with subsequent exposure.
• Antigens include allergens, bacteria and viruses. Usually
proteins, may be polysaccharides, lipids or nucleic acids.
• Origin: within the body or externally
Prof. Dr Shahina Yasmin
, Antigens
Antigen: Molecules which react/bind with antibody,
( product of immune response)
Immunogen: Molecules which induce an immune response
• Any foreign or endogenous substance that elicits an
immune response when introduced into tissues/
susceptible animal.
• All immunogens are antigens, all antigens are not
immunogens
Haptens: small univalent molecules which can react with
specific antibody but not immunogenic.
• These combine with carrier proteins to be immunogenic.
Able to cross link with antibodies eg. penicillin, poison ivy.
• can not bind with MHC Class II molecules but bind with
carrier protein.
, Antigens
• Antigen antibody reaction is highly specific. Lock and key
model
• Antigen and antibody bind with weak forces such as
hydrogen bonds and Vander Waals forces.
• Affinity (strength of binding) depends upon the fit of
antigen at binding site and ability to form more bonds.
Affinity increases with subsequent exposure.
• Antigens include allergens, bacteria and viruses. Usually
proteins, may be polysaccharides, lipids or nucleic acids.
• Origin: within the body or externally
