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Abstract Continuous human lymphoblastoid cell lines (LL), derived from lymphoid tissue or peripheral blood of 20 adults without histories of recent infectious mononucleosis at a frequency close to 100 %, were examined for the presence of Epstein‐Barr virus (EBV) using immunofluorescence methods for the detection of EBV‐dependent cell membrane and EB viral capsid antigens. All lines except one were found to be EBV carriers in the initial tests, but the antigens gradually disappeared in most during the course of an observation period of 4 months. Only eight lines maintained the initial percentage of antigen‐containing cells. The results of the two immunofluorescence tests, performed simultaneously on each cell pool, were concordant in all instances. Sera were available from 16/20 donors. All cell donors, except one, possessed antibodies to EBV as an indication of prior EBV infections. The growth‐promoting role of EBV in the establishment of LL was supported by studies with fetal lymphoid tissue cultured by the same grid method which yielded the high frequency of LL from adults. In sharp contrast to the results obtained with adult lymphoid tissue, no lines were established from 20 fetuses aged 13‐20 weeks. However, when such tissue was exposed to a cell‐free filtrate prepared from an EBV‐carrying LL lymphoblastoid cell, lines were established in some instances. Filtrate from an EBV‐negative line inoculated into parallel cultures failed to promote the establishment of LL. The results indicate that EBV infection in vivo or in vitro may be a prerequisite for the indefinite growth of lymphoblastoid cells in vitro and that EBV infections, as a rule, are not vertically transmitted.
Nilsson et al. (Mon,) studied this question.