(A) Proliferation of P-NK-92 and selected TR-IL-2-NK-92 in cultures not supplemented with exogenous IL-2. For culture of P-NK-92 cells, exogenous IL-2 was removed just before day 0. One of 2 experiments performed is shown. (B) Proliferation of TR-IL-2-NK-92 cells and NK-92 cells transduced with the retroviral vector containing the IRAP gene as control. The latter were IL-2–dependent and were cultured in the presence of exogenous IL-2. Note that the growth rates of transduced experimental and control NK-92 cells were similar.