Oncostatin M production by human dendritic cells in response to bacterial products

Oncostatin M (OSM) is a pleiomorphic cytokine that belongs to the IL-6 cytokine family. It is produced by activated T cells and monocytes/macrophages and plays an important role in the process of inflammatory responses. Although dendritic cells (DCs) have been shown to secrete a variety of cytokines, it is not elucidated whether DCs are able to produce OSM. To clarify this, using human DCs derived from peripheral blood cells, we measured the protein levels of OSM in the supernatants of DC cultures by ELISA and examined the expression of OSM mRNA by RT-PCR after stimulation with lipopolysaccharide (LPS) or fixed Staphylococcus aureus (SACS). Upon stimulation with bacterial products, DCs secreted a large amount of OSM protein in a dose- and time-dependent manner. Concomitantly, the expression of OSM mRNA by DCs was markedly up-regulated. Compared the ability of DCs to produce OSM with that of monocytes, which are major producers of OSM, DCs released significantly higher amounts of OSM protein in the culture supernatants than monocytes. These findings indicate for the first time that human monocyte-derived DCs can synthesize and secrete large amounts of OSM in response to bacterial products, suggesting that OSM produced by DCs at infectious sites may play a role in modulating inflammatory responses.