This study examined the effect of IL-10 on immunoglobulin-like transcript (ILT4) expression of human monocytic leukemic cell line THP-1, especially the role of the ILT4 promoter activity.ILT4 promoter area was amplified by PCR, and was cloned into the eukaryotic expressing vector pGL3-Basic.The pGL3-ILTP obtained was tested by double endonuclease digestion and sequencing.Then, the recombinant plasmid was transfected into THP-1 cells by using lipofectamine.After culture with IL-10 for 12 h, the mRNA extracted from THP-1 cells was detected by RT-PCR and the protein was detected by FACS.The dual-luciferase reporter assay system was employed to detect the activity of ILT4 promoter with or without IL-10.The results showed that the activity of pGL3-ILTP was significantly increased and was more than ten times that of pGL3-Basic cells.After culture with IL-10 for 12 h, the expression of ILT4 protein and its mean fluorescence intensity (MFI) were increased.Moreover, the mRNA was remarkably higher than that of the control group.Dual-luciferase reporter assay revealed that ILT4 promoter was much more activated after being treated with IL-10.We were led to conclude that pGL3-ILTP containing ILT4 promoter was constructed successfully.The expression of ILT4 could be up-regulated by IL-10 both at the transcriptional and translational level.Furthermore, ILT4 promoter could be much more active after addition of IL-10.This study suggests that IL-10 up-regulates ILT4 expression on monocytes via increasing ILT4 gene promoter activity, which may have implication for inducing transplantation tolerance in clinical practice.
