Cytokine mediated growth inhibition of HTLV-I infected transformed human lymphocytes

The interaction between HTLV-I infected immortalized cells and transformed cells was studied. HTLV-I infected immortalized human lymphocytes (Coculture-5) dependent of IL-2 medium (IL-2+PHA+TPA) and transformed cells (UV-5) derived from Coculture-5 following UV irradiation were cocultured in equal numbers in IL-2 medium. UV-5 cells were suppressed and disappeared about 1 month in cocultivation. UV-5 cells were not suppressed in IL-2 medium. Coculture-5 cells and UV-5 cells were seeded in Transwell dishes that were separated by membrane with pores 0.4 micron in diameter and cultured in IL-2 medium. UV-5 cells were suppressed indicating that cell-cell contact was not required for the observed suppression. UV-5 cells were markedly suppressed in IL-2 medium harvested from Coculture-5 cells when recombinant interferon alpha (1000 U/ml) was added to the medium. These findings demonstrated that growth of HTLV-I infected transformed cells could be suppressed by cytokine(s) released by HTLV-I carrier lymphocytes.