CS1-4 reacts strongly with EBV-positive lymphoblastoid cell lines and EBV infected B cell immunoblasts in infectious mononucleosis. It also reacts with 25 to 50 per cent of EBV-associated undifferentiated nasopharyngeal carcinomas and with Reed Sternberg cells in approximately 90% of EBV-associated Hodgkin’s lymphoma cases. The cocktail recognizes distinct epitopes on the hydrophilic carboxyl region of LMP which is exposed to the cytosol.