Induction of autologous CLL-specific CTL responses by DCs transfected with whole-tumor RNA. Immature DCs generated from the peripheral blood of 2 patients with CLL (A, patient no. 1; B, patient no. 2) were electroporated with 10 μg whole-tumor RNA isolated from autologous malignant B cells. After further incubation with 10 ng/mL TNF-α for 24 hours DCs were used as APCs for in vitro CTL induction. Cytolytic activity of the CTLs was determined on day 5 after the last restimulation by using autologous purified leukemic cells or nonmalignant B lymphocytes as targets in a standard ⁵¹Cr-release assay. Blocking of HLA class I molecules with the monoclonal antibody W06/32 was performed to analyze the HLA class I restriction of the elicited CTL responses. K562 tumor cells were included to determine the NK cell activity. A cold target inhibition assay was performed to further assess the specificity of the CTLs induced with the DCs from patient no. 1 (C). The lysis of autologous CLL cells (pulsed with ⁵¹Cr, hot targets) could be blocked by addition of unpulsed autologous CLL cells (cold targets) but not by nonmalignant autologous peripheral blood mononuclear cells (PBMNCs).