Which part of bacteria is most antigenic-
Proteins are most immunogenic, while lipids & nucleic acids arc least immunogenic.
Polysaccharides (carbohydrates) are less immunogenic than protein antigens, but are more antigenic than lipids &nucleic acids.
 
Determinants of antigenicity
A number of properties of antigen determine its antigenicity (production of antibody or induction of cell mediated immunity):
 
Chemical nature
Proteins > Polysaccharide > lipids and nucleic acids.
All proteins except gelatin arc immunogenic.
 
Size
High molecular weight particles > low molecular weight particles.
 
Foreign ness
In general, molecules recognized as "self are not immunogenic; for immunogenicity, molecules must be recognized as "nonself".
 
Susceptibility to tissue enzymes
Only substances which are metabolized and are susceptible to the action of tissue enzymes behave as antigens.
 
Route of administration
Parenteral > oral
Protein coat
Lipopolysaccharide
Nucleic acid
Lipids