BETA(2)-MICROGLOBULIN AND HLA-DR EXPRESSION IN RELATION TO THE PRESENCE OF EPSTEIN-BARR-VIRUS IN NASOPHARYNGEAL CARCINOMAS

We have investigated the immunohistochemical expression of beta(2)-mic roglobulin and HLA-DR proteins in nasopharyngeal carcinoma (NPC) in re lation to the expression of the Epstein-Barr virus (EBV)-encoded EBER 1-2 mRNAs and LMP-1 protein. beta(2)-Microglobulin is expressed in ass ociation with MHC-I molecules on most nucleated cells and HLA-DR belon gs to the MHC-II molecules which are expressed mostly on antigen-prese nting cells, Formalin-fixed paraffin-embedded tissue from 37 NPC cases was stained with immunohistochemistry for beta(2)-microglobulin, HLA- DR and LMP-1 proteins and by RNA in situ hybridization for EBER 1-2 mR NAs. beta(2)-Microglobulin-positive staining was found in neoplastic c ells in all cases, In 19/37 NPC cases the positive staining was found in most neoplastic cells. In the remaining 18 NPC cases more than 25% of the neoplastic cells showed significantly reduced or negative stain ing in comparison to the normal epithelium and infiltrating small lymp hocytes. HLA-DR-positive staining was found in 27/37 NPC cases. EBER 1 -2 transcripts were deteced in neoplastic cells in 13/37 NPC cases. LM P-1 expression in tumour cells was found in 4/13 EBER 1-2 positive cas es. No correlation was found between the presence of EBER 1-2 transcri pts or LMP-1 protein and the beta(2)-microglobulin-reduced expression in NPC. Thus, EBV does not seem to use downregulation of MHC-I to avoi d the T cell cytotoxic immune response in NPC. HLA-DR expression was o bserved in all 13 EBV-positive cases of NPC, suggesting that EBV may p articipate in the induction of HLA-DR expression in a proportion of NP C.