THE EXPRESSION OF EPSTEIN-BARR-VIRUS LATENT PROTEINS IS RELATED TO THE PATHOLOGICAL FEATURES OF POSTTRANSPLANT LYMPHOPROLIFERATIVE DISORDERS

Transplant recipients are at increased risk for the development of pos t-transplant lymphoproliferative disorders (PTLDs). PTLDs harbor genom es of the Epstein-Barr virus, a herpesvirus that immortalizes B cells in vitro At least five viral proteins are required for immortalization . Two of them are particularly important. Latent membrane protein (LMP ) has transforming activity, in fibroblasts, and Epstein-Barr antigen (EBNA)2 transactivates the expression of numerous cellular and viral g enes To determine whether the expression of EBNA2 and LMP is related t o the histological and clinical presentation of PTLD, we tested their expression in 14 Epstein-Barr virus-positive cases. Using monoclonal a ntibodies to EBNA2 and LMP on paraffin sections, we found an expressio n of both proteins in 2 of 3 polymorphic PTLD and in 7 of 8 cases of m onomorphic, large cell PTLD, without plasmacytic differentiation One p olymorphic and one large cell PTLD expressed LMP only. LMP and EBNA2 w ere found particularly in immunoblasts. The number of positive cells w as extremely variable in the different cases as well as within the sam e biopsy. Three cases of PTLD had morphological and phenotypical featu res of plasmacytomas and did not stain for EBNA2 or LMP. This suggests that the expression of EBNA2 and LMP is related to the differentiatio n stage of the infected cells and that other viral or cellular protein s may contribute to tumor growth.