In vitro proliferation and functional activation of V alpha 24NKT cells following stimulation with alpha -galactosylceramide (alpha -GalCer)-pulsed dendritic cells (DCs) have been observed. Because little is known about the molecular events on DCs following interaction with alpha -GalCer, we performed gene expression profiling of 2400 genes in monocytes and monocyte-derived immature DCs pulsed with alpha -GalCer (alpha -GalCer-imDCs). Overall, the expression levels of 48 genes were up-regulated and 28 were down-regulated in alpha -GalCer-imDCs. Semiquantitative RT-PCR analysis on monocytes, imDCs, alpha -GalCer-imDCs, and mature DCs confirmed the up- and down-regulation of the mRNA expression levels of 28 selected genes. Notably, we identified the specific up-regulation of mRNA expression levels of ribonuclease A and collapsin response mediator protein upon the stimulation of imDC with alpha -GalCer, suggesting a novel immunomodulating effect of alpha -GalCer on imDCs. In this study, we used imDCs prepared by culturing of monocytes with GM-CSF and IL-4 for 5 days and mDCs prepared by further culturing of imDCs with TNF alpha for two extra days.