Heterophile antigen
Heterophile antigens: certain antigens of similar nature, if not identical, present in different tissues in different biological species, classes or kingdoms.Usually different species have different antigen set but hetereophile / hetereogenetic antigen is shared by different species. Other heterophile antigen are responsible for some diagnostic serological test such as
Weil felix reaction for typhus fever
Paul bunnell test for infectious mononucleosis
Cold aglutinin test in Primary atypical pneumonia
Composition: chemically these are lipoprotein-polysaccharide complexes, possibly there are identical chemical groupings in the structure of mucopolysaccharids and lipids. Example: Forssman antigen, cross reacting microbial antigen so antibodies to these antigens produced by one species cross react with antigens of other species. It is widely present in some plants bacteria animal and birds. However it is not present in rabbit. Therefore antibodies are produced in rabit serum by injecting antigen(antiforssman antibodies)