Expression of macrophage‐derived chemokine (MDC) mRNA in macrophages is enhanced by interleukin‐1 β, tumor necrosis factor α, and lipopolysaccharide

A cDNA encoding the CC chemokine MDC was isolated from a human macrophage cDNA library by differential hybridization using monocyte‐ and macrophage‐specific cDNA probes. During monocyte to macrophage differentiation in vitro, MDC expression is first detected after 1 day of culturing and reaches maximum levels after 6 days when macrophages have fully matured, as judged from the expression of known macrophage marker genes. Exposure of macrophages to lipopolysaccharide (LPS) results in a dose‐dependent increase in MDC mRNA levels, with maximum induction occurring after 6–8 h, whereas expression levels of macrophage inflammatory protein‐1α (MIP‐1α), MIP‐2, interleukin‐1β (IL‐1β), and tumor necrosis factor α (TNF‐α) respond much faster to LPS. Furthermore, MDC expression in macrophages is enhanced by the inflammatory mediators TNF‐α and IL‐1β. Similar to other TNF‐α/IL‐1β‐inducible genes, costimulation of macrophages with both cytokines leads to higher MDC expression levels than stimulation with a single cytokine. By contrast, both resting and activated monocytes do not express MDC mRNA. J. Leukoc. Biol . 63: 606–611; 1998.