HETEROPHILE ANTIGEN AND ANTIBODY

Similar antigens present on dissimilar organisms are heterophile antigens. Closely related antigens can occur on widely different organisms. Antibodies reacting with such antigens are called heterophile antibodies. Serologic tests employing these heterophile antigens are called Heterophile tests.

Examples:

1. Forssman antigen: It is a lipid-carbohydrate complex widely distributed in human, animals, birds, plants, and bacteria. Distribution of Forssman antigen:
   � Erythrocytes of horse, cat, mouse, sheep, chicken
   � Kidney cells of guinea pig.
   � S.pneumoniae, S.dysenteriae, Pasteurella, C.perfringens and some Salmonella species.

2. Other Heterophile antigens:
   � Blood group B antigen and E.coli O86
   � Blood group A antigen and Pneumococcal type 14 capsular polysaccharide.
   � Blood group P1 antigen and Hydatid cyst fluid.
   � Blood group A antigen and Streptococcal extracts.

Heterophile tests:

• Weil-Felix test: Patients suffering from certain rickettsial diseases will produce antibodies that will react and agglutinate certain non-motile strains of Proteus (OXK, OX2, and OX19).

• Paul-Bunnel test: patients suffering from infectious mononucleosis due to EBV will produce antibodies that will react and agglutinate sheep erythrocytes.

• Cold agglutination test: Patients suffering from atypical pneumonia due to Mycoplasma pneumoniae will produce antibodies that will react and agglutinate human O group RBC at 4^oC.

• Streptococcus MG agglutination test: Patients suffering from Mycoplasma pneumoniae develop heterophile antibodies to Streptococcus MG, which are titrated in a tube agglutination test.