“…This is made evident by: (1) NPC patients showing a different pattern of humoral immune responses to EBV antigens from that shown by control groups of non-NPC subjects (Henle et al, 1970;Henle et al, 1973;de Schryver et al, 1974;de-The et al, 1975;Ho et al, 1977b;Ng, Ho and Kwan, 1977) and (2) the persistent presence of EBV genomes and EBV nuclear antigen(s) in NPC cells (Desgranges et al, 1975;Huang et al, 1974;Wolf, Zur Hausen and Becker, 1973;Klein et al, 1974). The resident EBV genomes may be activated to synthesize early viral antigens and/or virus particles when NPC cells have been treated with IUdR and BUdR respectively (Glaser et al, 1976;Trumper, Epstein and Giovanella, 1976).…”