[Different Echinococcus granulosus antigens induced indoleamine 2,3-dioxygenase expression in dendritic cells].

Objective: To observe the expression of indoleamine 2, 3-dioxygenase (IDO) in dendritic cells (DCs) via different Echinococcus granulosus antigens in vitro.

Methods: Bone Marrow DCs generated from bone marrow precursor cells of C57BL/6 mice and cultured in the presence of recombinant mouse GM-CSF (rmGM-CSF). Then, DCs were induced with 15 microg/ml recombinant antigen B (rAgB), 5 mg/ml mouse hydatid fluid (MHF), 1,000 U/ml IFN-gamma (as positive control), and RPMI 1640 complete medium (as negative control), respectively. Meanwhile, the treated DCs and cell supernatants were collected at 18, 24 and 48 h after induction. The positive expressions of D40, CD80, CD86 and I- A/I-E on DCs were determined by flow cytometry. By real-time fluorescent quantitative reverse-transcription polymerase chain reaction (FQ-RT-PCR), the expression level of IDO mRNA in DCs was measured. Concentrations of tryptophan (Try) were tested by high-performance liquid chromatography (HPLC) assay in cell supernatant.

Results: The data from flow cytometry showed that the positive expressions of CD40, CD80, CD86, I-A/I-E were decreased after stimulated by rAgB and MHF. At 24 h after induction, there was significant difference in the level of CD40, CD86 and I-A/I-E among rAgB-treated group [(22.60 +/- 2.69)%, (35.50 +/- 4.38)%, (57.30 +/- 4.38)%], MHF-treated group [(38.00 +/- 3.54)%, (53.00 +/- 3.39)%, (77.10 +/- 1.70)%] and negative control [(37.95 +/- 3.61)%, (19.55 +/- 1.06)% and (85.45 +/-1.63)%] (P < 0.05). At 18, 24 and 48 h after induction, the levels of IDO mRNA in rAgB-treated group [(9.20 +/- 0.01), (29.44 +/- 0.02), (16.48 +/- 0.04)] and MHF-treated group [(9.67 +/- 0.02), (17.52 +/- 0.01), (16.81 +/- 0.01)] was higher than that of negative control group [(2.46 +/- 0.01), (7.77 +/- 0.01), and (10.56 +/- 0.01)] (P < 0.01). And significant difference was found between rAgB-treated group and MHF-treated group (P < 0.05). At 18, 24 and 48 h after induction, the concentrations of Try were lowest in rAgB-treated group [(23.65 +/- 0.64), (13.95 +/- +1.06), (19.0 +/- 00.64) micro.mol/L]. At 24h after induction, Try concentration in negative control group (22.9 +/- 0.14) was higher than that of MHF-treated group (20.65 +/- 0.34) ( P < 0.05).

Conclusion: Under in vitro condition, rAgB and MHF can up-regulate IDO expression. The ability of rAgB to up-regulate IDO activity was stronger than that of MHF at 24 h after induction.