Mononucleosis antigen is a glycoprotein purified from bovine erythrocytes, suitable to produce reagents similar to the Oxoid latex, or other forms of immune techniques (lateral flow, as example) to detect heterophile antibodies (Paul Bunnel, etc). It is a freeze-dried powder suitable to detect human heterophile antibodies or Paul-Bunnel antibodies, as appears in human Infectious Mononucleosis. It is a glycoprotein purified from bovine red cells. It is antigenically related to Epstein- Barr virus.