The immortalization of human lymphocytes by spheroplast fusion

A method for immortalizing animal cells based on the spheroplast fusion technique of Schaffner is being developed. Human lymphocytes have been fused with E. coli spheroplasts containing the plasmid pTSV3, which represents the entire SV40 genome cloned into the EcoRI restriction enzyme site of the plasmid pAT153. The efficiency of transformation was examined using pTSV3 and derivatives which have deletions in parts of the late gene sequences. Although there was a marked increase in the survival time of the lymphocyte cultures after fusion compared with cells which had been mitogen-stimulated but not fused, the cells did not continue to proliferate indefinitely. Attempts are now being made to extend the survival time by culturing the transformed lymphocytes in the presence of feeder cells.