IL15 and cervical cancer: The direct cytotoxicity of HPV vaccine-stimulated IL-15 DC (i.e. Cer-DC) was examined in a flow cytometric lysis assay by co-culturing DC with the HPV16+ cervical cancer cell line CaSki, the HPV18+ cervical cell line HeLa or the HPV− CML cell line K562 for 4 hrs at an effector:target (E:T) ratio of 5:1 and 50:1.