Induction of P198-specific CTLs by immunization with peptide-pulsed DCs activated by CD40 triggering. Mice were injected subcutaneously in the footpads on days 0 and 14 with 3 x 10⁵ P198-loaded DCs either previously cocultured with CD40L-transfected 3T3 cells (CD40L-activated DC + peptide P198) or untreated (DC + peptide P198). Spleen cells from injected mice were harvested on day 21 and stimulated in vitro with P198 tumor cells. Six days later, these cultures were submitted to a second short-term stimulation (4 days) with P198 tumor cells and subsequently tested on ⁵¹Cr-labeled P198 or L1210 tumor cells loaded or not with the P198 peptide in a three hours and half chromium release assay. Each curve gives the CTL response of spleen cells from an individually injected mouse. Data are from one representative experiment of 4 performed.