T cell growth factor from human splenic cell cultures: conditions for its production, and its utilization for maintenance of cytotoxic T cell lines.

We prepared the T cell growth factor (TCGF) from human spleen cell cultures stimulated with phytohemagglutinin (PHA). Various cell culture conditions and agents supporting the active TCGF production of the spleen cells were examined. The highest TCGF activity was obtained in the supernatants under the conditions that 2 x 10(6)/ml spleen cells were stimulated with PHA for 48 hr. Production of TCGF from spleen cells depended markedly on their individual sources. Addition of indomethacin to the culture or irradiation of the responding spleen cells increased TCGF activity in the supernatant of the culture. Further, addition of irradiated cells of an Epstein-Barr virus (EBV)-transformed lymphoblastoid cell line (LCL) to spleen cell cultures stimulated with PHA greatly enhanced TCGF production. Human splenic TCGF facilitated the establishment of human cytotoxic T cell (Tc) lines specific for EBV-transformed LCL cells when those Tc line cells were stimulated periodically with irradiated autologous LCL cells but not with the other two types (K-562 or Molt-4) of cells. Allogeneic LCL stimulators allowed the Tc line cells to proliferate. However, Tc line cells cocultured once with allogeneic LCL stimulators no longer exhibited EBV-specificity in their cytotoxicities.