Human monocyte-derived dendritic cells produce bioactive gelatinase B: inhibition by IFN-beta.

We studied the secretion of gelatinase B by dendritic cells (DC) generated by culturing human peripheral blood monocytes in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). First, we found the intracellular expression of gelatinase B on sections of fixed DC pellets. Zymography analysis of the supernatants of DC cultured for 72 h demonstrated the presence of gelatinase B. To determine if DC produce net enzymatic activity, bioactive gelatinase, a novel sensitive fluorescent-activated substrate conversion (FASC) assay was used to complement the zymography data. Culture media of unstimulated DC demonstrated reproducible net gelatinolytic activity. Tumor necrosis factor-alpha (TNF-alpha) IL-1beta but not lipopolysaccharide (LPS) stimulation caused a significant increase in gelatinase B production in zymography analysis. Both types of stimulation failed to increase net gelatinase activity in FASC assay. Interestingly, interferon-beta (IFN-beta) significantly diminished both the total zymolytic production and the net bioactive gelatinase produced by DC in a dose-dependent manner. We conclude that human monocyte-derived DC secrete bioactive gelatinase B and that IFN-beta inhibits this production.