IL-6 modulates pDC maturation.

<p>Human pDCs from healthy volunteers were either treated with 50 ng/ml of IL-6 or cultured only in the presence of 10 ng/ml of IL-3 (to maintain pDC viability), with or without stimulation with CpG, for two days. IL-6 inhibits the phenotypic maturation induced by the culture with IL-3. In contrast, IL-6 further upregulates CD40 expression on pDCs when stimulated with CpG-rich hypomethylated oligodeoxynucleotides (mimicking fragments of microbial DNA). Freshly isolated pDCs at d0 consistently had high levels of HLA-DR expression and typically low levels of CD86 and CD40, whereas the staining intensities for CD80 and ICOS-L were at the isotype control level (data not shown). % expression values (in the bottom right part of the figure) were calculated for each experiment ((expression in the presence of IL-6/expression in the absence of IL-6) ×100) and presented as mean ± SD. Flow cytometry data from five independent experiments are presented. * <i>P</i><0.05; ** <i>P</i><0.01.