Method: We included 10 SLE patients (4 with SLEDAI=0, 6 with SLEDAI>6) as well as 10 healthy controls. Peripheral blood mononuclear cells were isolated by Ficoll-Hypaque centrifugation. Monocytes were purified by positive selection with anti-CD14 mAb coated microbeads. DC were generated by culturing monocytes for 6 days in presence of GM-CSF, IL-4 and for 2 additional days in presence of LPS to induce maturation. In vitro generated DC as well as peripheral blood DC defined by the following phenotype, Lin-HLA-DR+CD11c-BDCA-4+, were analyzed for HLA-DR, CD40, IRF3, and IRF5 expression by flow cytometry and Western Blot.
Result: We found that immature DC from SLE patients shown significantly diminished levels of the CD40 molecule (percentage of CD40+ DC: control median= 48.8, SLE median= 28, p=0.03). In addition, we observed that expression of IRF-3 and IRF-5 on mature DC from SLE tended to be higher compared with controls (IRF3 MFI mean= 17.7 in controls versus 32.5 in SLE; IRF5 MFI mean=22.1 in controls versus 30.01 in SLE). Furthermore, we found that the expression of these molecules was increased in peripheral blood Lin-HLA-DR+CD11c-BDCA-4+ DC from SLE patients compared with healthy controls (percentage of IRF3 positive cells= 29 in controls versus 76 in SLE; percentage of IRF5 positive cells= 3.6 in controls versus 34.6 in SLE). We found no differences on IRF expression on DC from active SLE and those with inactive disease.
Conclusion: Our results suggest that the previously reported elevated levels of IFN-I observed in SLE might be explained by the altered expression of IRF on DC from SLE patients. Furthermore, the impaired expression of these factors might be considered as an intrinsic defect in SLE.
Disclosure: K. Santana-de Anda, None; A. E. Monsivais-Urenda, None; D. Gomez-Martin, None; J. Cruz-Ruiz, None; J. Alcocer-Varela, None.