Induction of CTLs in vitro by using amplified CLL RNA. The cytotoxicity of CTLs induced with autologous DCs that were electroporated with native total CLL RNA or amplified CLL mRNA isolated from autologous CLL cells was analyzed in a standard ⁵¹Cr-release assay by using autologous purified leukemic cells or nonmalignant B lymphocytes as targets. Inhibition of HLA class I or class II molecules was performed by incubating DCs for 1 hour prior to the assay either with the mAb W06/32 (directed against HLA class I) or Tü39 (directed against HLA class II molecules).