Flow cytometric characterisation of antigen presenting dendritic cells after in vitro exposure to diesel exhaust particles

The aim of this study was to obtain more insight into the effect of diesel exhaust particles (DEP) on the maturation of primary human dendritic cells. Monocyte-derived dendritic cells (Mo-DC) derived from seven different donors were exposed to different DEP concentrations (0.2, 2, 20, 200 and 2000 ng/ml) in the presence or absence of lipopolysaccharide (LPS), and changes in the surface expression of HLA-DR, CD86 and CD83 were examined. Exposure of Mo-DC to DEP alone did not alter expression levels of any of the markers. Treatment with LPS alone increased the expression levels of all three surface markers, although the levels were not significantly different compared to untreated DCs. The LPS-induced marker expression could be further enhanced by co-stimulation of the cells with DEP. Statistical significantly increased levels of CD83 expression were observed after exposure to 0.2 (p = 0.018), 20 (p = 0.010) and 200 ng/ml (p = 0.047) DEP combined with LPS in the group of responders. We conclude that DEP has an adjuvant effect on LPS-induced maturation of Mo-DC.