[Effect of high dose dexamethasone on function and TLR-9 mRNA expression of plasmacytoid dendritic cells in patients with immune thrombocytopenic purpura].

This study was purposed to investigate the effect of high-dose dexamethasone (DXM) on function and Toll like receptor 9 (TLR-9) expression of plasmacytoid dendritic cells (pDC) in peripheral blood of patients with immune thrombocytopenic purpura (ITP). 15 newly diagnosed patients with ITP received high dose DXM at single daily doses of 40 mg for 4 consecutive days. The peripheral blood plasmacytoid dendritic cells from 13 remission patients and 15 normal controls were separated by immunomagnetic beads and then induced by CpG-OND2216. 24 h later, the levels of IFN-α, IL-6 and TNF-α in the supernatant were detected by enzyme linked immunosorbent assay (ELISA). The expression of TLR9 mRNA of pDC was detected by real-time quantitative PCR. The results indicated that the levels of IFN-α, IL-6 and TNF-α produced by pDC in ITP patients were significantly higher than those in normal controls (P < 0.05). After high dose DXM treatment, the levels of IFN-α, IL-6 and TNF-α decreased without significant difference compared with normal controls (P > 0.05). The expression of TLR9 mRNA in pDC of untreated patients was significantly higher than that in control group (P < 0.05), and significantly reduced after treatment without difference from that in control group (P > 0.05). It is concluded that pDC may play an important role in ITP by their TLR9 and secreted cytokines; dexamethasone may down regulate the expression of TLR9, inhibit pDC function, and thus play a therapeutic role.