Expression of DC-CK1, IL-12, and IL-18 by in vitro–generated DC. PBMNC were cultured with the indicated combinations of cytokines for 7 days. Total RNA was isolated from cultured DC, purified CD14⁺ and CD34⁺ cells, or human tumor cell lines. DC-CK1, IL-12, and IL-18 expression was examined by semiquantitative RT-PCR. Twenty-eight rounds of amplification using primers specific for DC-CK1 and IL-18, 32 cycles for IL-12 amplification, and 23 cycles for β₂-microglobulin were performed. PCR products were run on a 3% agarose gel and visualized by ethidium bromide staining. Samples containing no cDNA were used as negative control.