OBJECTIVETo study the surface antigen of the dendritic cells (DC) and their Toll-like receptor 4 (TLR4) expression in patients with idiopathic thrombocytopenic purpura (ITP), and to explore their role in ITP pathogenesis.

METHODSThe peripheral blood mononuclear cells isolated from complete remission patients (CR), non-complete remission patients (n-CR) and normal controls were stimulated by rhGM-CSF and rhIL-4. The surface antigen of the DC was analyzed by flow cytometry. The level of IL-12p70 in the supernatant was detected by enzyme linked immunosorbent assay. The expression of TLR4 mRNA of DC was detected by real time PCR.

RESULTSIn the 21 CR ITP patients, the expression of both CD80 and CD86 in DC was significantly increased compared with that in normal controls \[(51.60 ± 13.47)% vs (36.03 ± 15.43)%, (61.50 ± 15.93)% vs (40.28 ± 11.49)%, respectively\] (P < 0.01). The expression of CD80 and CD86 in n-CR group was also significantly increased \[(53.29 ± 19.49)% and (62.91 ± 18.43)%, respectively\] (P < 0.01). After HD-DXM treatment, both CD80 and CD86 in CR patients were decreased (P < 0.01). There was no difference between the DXM treatment patients and the normal controls. In n-CR group, there was no difference in CD80 and CD86 expression before and after DXM therapy \[(52.30 ± 20.98% and (49.79 ± 20.28)%, respectively\] (P > 0.05). CD80 was still higher than normal (P < 0.05), while CD86 was not changed. The level of IL-12p70 in CR ITP patients before treatment was significantly higher \[(67.52 ± 14.43) pg/ml\] than that of the controls \[(39.78 ± 10.03) pg/ml\](P < 0.01), and after treatment, was significantly decreased to (43.90 ± 8.49) pg/ml, being no difference from that in control. In n-CR group, IL-12p70 was lower after treatment \[(48.45 ± 9.68) pg/ml\] than that before treatment \[(65.35 ± 12.52) pg/ml\] (P < 0.01), but still higher than that in control (P < 0.05). The TLR4 mRNA level in DCs of CR ITP patients before treatment were significantly higher 0.69 ± 0.17 than that of controls (0.31 ± 0.09) (P < 0.01) and after treatment, was reduced to 0.35 ± 0.11, being no difference from that in control. In n-CR group, TLR4 mRNA was decreased from 0.65 ± 0.09 to 0.52 ± 0.21 after treatment (P < 0.01), but still higher than normal (P < 0.01).

CONCLUSIONDC may play an important role in ITP by their Toll-like receptor and cytokine secretion.