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The ability of a particular substance (antigen) to provoke an immune response.


The ability to induce humoral and/or cell mediated immune responses

The ability of antigen to elicit immune response is called “Immunogenicity”.

Antigens that do provoke the immune response are called-”immunogens”

Immunogenic Potency of antigens

Proteins>>>Polysaccharides Lipids, Nucleic acids serve as immunogens only when they are in combination with proteins/polysaccharides.

-For studies of humoral immune response – proteins/ polysaccharides are used

-For cell-mediated immunity – only proteins serve as immunogens

Factors influencing immunogenicity

->Contribution of antigen to immunogennicity

->Contribution of Biological system to immunogenicity

Antigen and Immunogenicity

see the diagram

Immunogenicity is influenced by different factors of an antigen:

-Foreignness Phylogenetic distance – immunogeniciry

-Molecular size

-Epitope density

-Chemical composition and heterogeneity Protein structure, aa-polymers, Glu-Lys, Tyr, Phe -Degradability (ability to be processed & presented to T cells) D-amino acids