Expression of latent membrane protein 1 in clinically isolated cases and animal models of AIDS‐associated non‐Hodgkin's lymphomas

Epstein‐Barr virus (EBV)‐encoded latent membrane protein 1 (LMPl) Is known to be expressed in non‐Hodgkin's lymphomas (NHL) occurring In immunocompromlsed hosts, playing crucial roles In lymphomagenesis. LMPl expression at the microscopic level, however, was reported to be limited to some, not all, neoplastic cells In each specimen studied. In order to determine whether LMPl expression of NHL really Is IlmM to some cells, fhm cllnlcally Isolated acquired lmmunodeficlency syndrome (AIDS)‐associated and six experimental NHL were studied lmmunohlstochemlcally, Immuno‐eleclron mlcroscopically and flow cytometrically. The experimental models were the lymphocytic tumors produced In mere combined Immune deficiency (SCID) mice after engrattlng EBV‐infected B cells. Light microscopy revealed Intense LMP1‐immunostalnlng in less than 5% of neoplastic cells in the NHL, weak staining in less than 50% and apparently unstained cells in over 50%. Immunoelectron microscopy revealed that the intensely stained cells were those undergoing degeneration, whereas a proportion of the remainder demonstrated patchy reactions on their cell membranes. The weakly stained cells were found to correspond to cells with several patches on their cell membranes. Flow‐cytometric analysis demonstrated that a large proportion of the neoplastic cells expressed LMPl to some extent. Taken together, the resutts suggest that most of the neoplastic cells expressed UP1 molecules at quantitatively different levels, some of which were below the level detectable by light microscopy. The intensely stained cells were shown to be those undergoing degeneration.