Objective: To study the effect of interferon-alpha IFN-α in the serum of SLE patients on the differentiation and maturation of dendritic cells (DCs) derived from CD34+ hematopoietic precursor cells (HPCs). Methods: Serum samples from SLE patients and normal controls were collected and the concentration of IFN-α detected by ELISA. CD34+HPCs were purified from cord blood by a magnetic cell sorting system (MACS), and cultured to differentiate to DCs. Normal serum, normal serum with exogenous IFN-α, SLE serum with raised levels of IFN-α, or SLE serum with anti-IFN-α neutralizing antibody was added to the culture medium. The phenotype of DCs was analyzed by flow cytometry (FCM) and the capacity of DCs to stimulate allogenic T lymphocyte proliferation was evaluated in a mixed lymphocyte reaction by the Cell Counting Kit-8. Cytokine production was assessed by ELISA. Results: Serum levels of IFN-α were significantly higher in SLE patients than in normal controls and this correlated positively with disease activity. Cultured in SLE serum with raised levels of IFN-α, CD34+ HPCs could differentiate into DCs that expressed higher levels of HLA-DR, CD80 and CD86, and showed an enhanced allogenic T-cell stimulatory capacity, while producing lower levels of IL-12 and higher amounts of IL-10 compared with those DCs cultured in normal serum. Conclusion: Increased levels of IFN-α in SLE serum promotes the differentiation and maturation of DCs derived from CD34+ HPCs and could contribute to the pathogenesis of SLE.