In this report, we demonstrate that a fetal mouse skin-derived dendritic cell line produces nitric oxide (NO) in response to the endotoxin [lipopolysaccharide (LPS)] and to cytokines [tumor necrosis factor-α (TNF-α) and granulocyte-macrophage colony-stimulating factor (GM-CSF)]. Expression of the inducible isoform of NO synthase (iNOS) was confirmed by immunofluorescence with an antibody against iNOS. The tyrosine kinase inhibitor genistein decreased LPS- and GM-CSF-induced nitrite ([Formula: see text]) production. The effect of LPS and cytokines on [Formula: see text] production was inhibited by the Janus kinase 2 (JAK2) inhibitor tyrphostin B42. The p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB-203580 also reduced the [Formula: see text] production evoked by LPS, TNF-α, or GM-CSF, but it was not as effective as tyrphostin B42. Inhibition of MAPK kinase with PD-098059 also slightly reduced the effect of TNF-α or GM-CSF on [Formula: see text]production. Immunocytochemistry studies revealed that the transcription factor nuclear factor-κB was translocated from the cytoplasm into the nuclei of fetal skin-derived dendritic cells (FSDC) stimulated with LPS, and this translocation was inhibited by tyrphostin B42. Our results show that JAK2 plays a major role in the induction of iNOS in FSDC.