The isolation and establishment of cell lines, THE-2 and THE-3, from transformed foci of human embryonic cells exposed to human leukemic culture fluid was described. A fraction of cells of both lines exhibited a specific immunofluorescent reaction with the serum of patients from which the initial leukemic cells were derived. Such reactivity decreased by the successive transfer of the culture. However, lowering the temperature of cultivation of the cells to suboptimal conditions (32°C), resulted in a marked increase or recovery in number of fluorescent cells. The implication of these findings to the hypothetical viral agent as a cause of the transformation phenomenon and of human leukemia was discussed.
The electron microscopy performed on ultrathin sections of transformed cell line THE-2 and THE-3 revealed the association of herpes-like virus particles in the cultured cells. The ultrastructure of these virus particles was similar to those reported to be present in cultured cells of Burkitt's lymphoma and in some leukemic cell lines established from American leukemia patients.