[ ABSTRACT] AIM: To investigate the differential expression of human leukocyte antigen-G ( HLA-G) isoforms and its receptors in human monocyte line THP-1 after human cytomegalovirus ( HCMV) infection for exploring the role of HLA-G in HCMV escaping the immune response of the organism .METHODS: THP-1 cells were infected with HCMV Towne strain.The expression of HLA-G isoforms at mRNA and protein levels was determined by RT-PCR and Western blot, respectively.The surface expression of HLA-G and its receptors ILT2/ILT4 and the cell viability were analyzed by flow cytometry.The levels of soluble HLA-G (sHLA-G) and IL-10 were measured by ELISA.RESULTS:After infection of the THP-1 cells with HCMV , no obvious apoptosis in the cells was observed , and the viability of the cells was high .A significant up-regulation of HLA-G1,-G3,-G4 and-G5 at mRNA expression level 1 d after infection was found , while the protein expression of HLA-G1 and HLA-G5 isoforms was mainly detected .The expression of HLA-G/ILT2/ILT4 was evi-dently up-regulated 1 d after infection .The level of sHLA-G was significantly increased 1 d after infection as compared with control group (P<0.01).The expression of IL-10 was obviously up-regulated 1 d post-infection as compared with control group.CONCLUSION:The differential expression of HLA-G isoforms and secretion of the receptors ILT 2/ILT4 and IL-10 in the THP-1 cells are induced after HCMV infection .This study provides experimental evidence for evaluating the immune mechanism of HCMV infection .