Forssman antigen

The Forssman Antigen is a glycolipid heterophil protein and a type of heterogenetic antigen found in certain animals like dogs, horses, cats, turtles and sheep, including enteric organisms such as pneumococci. In sheep, it is found in their erythrocytes but not on tissue and organs, except for hamsters and guinea pigs. The Forssman antigen is distinct from the Paul-Bunnell antigen, antibodies to which are diagnostic of glandular fever (infectious mononucleosis). Both antigens are present on the red blood cells of horse and sheep but guinea pig kidney cells have only the Forssman antigen. A serum positive for glandular fever therefore agglutinates horse or sheep red blood cells after absorption with guinea pig kidney (see Basson V, Sharp AA (May 1969). "Monospot: a differential slide test for infectious mononucleosis". J. Clin. Pathol. 22 (3): 324–5. doi:10.1136/jcp.22.3.324. PMC 474075. PMID 5814738.)