Abstract
Fresh nasopharyngeal carcinoma (NPC) biopsies were treated in several ways to yield satisfactory cell preparations for detection of Epstein‐Barr virus (EBV)‐associated nuclear antigen (EBNA) by anti‐complement immunofluorescence tests. If the cells were well dispersed (trypsinization or extensive mechanical dispersal) few or none of them were EBNA‐positive. In contrast, if the biopsy preparations contained small to moderately sized tissue fragments (touch preparations or limited mechanical dispersal), nuclear staining was detected in nearly every cell at the margin of the fragments or in cell sheets protruding from them. The stained cells corresponded to the carcinoma cells when compared to histologically stained replicate cell preparations. Nuclear staining was obtaining with anti‐EBNA positive sera [healthy donors, NPC patients, convalescents from infectious mononucleosis (IM)], shown to be free of antibodies to other nuclear antigens, but not with anti‐EBNA negative sera (healthy donors or patients in the early acute phase of IM). These results confirm and extend previous reports that the carcinoma cells harbor EBV genomes. The implications of these findings are discussed.