| Type I dendritic cells ( DC1 ) , the most potent professional antigen procession cells (APC) in vivo, play a crucial role in human adaptive immune response. DC1 activate host immune responses not only by their capturing and processing antigens to MHC-I and II molecules on the cellular surface of T lymphocytes, but also by their enhancing or regulating naive T cells for boosting specific immune reaction against viral infection. The DC1 function was found to be defective in human viral diseases such as HBV or HIV infection, but it is rarely reported in patients with chronic HCV infection. In order to explore whether changes of DC1 function and lymphocyte subsets are related to chronic HCV infection and analyze the relationship between them, the monocyte-derived dendritic cells (DC1) were induced fromperipheral blood mononuclear cells (PBMC) in presence of GM-CSF, IL-4 and TNF- and analyzed using flow cytometric analysis. Simultaneously we detected lymphocyte subsets in patients with chronic HCV infection. Clinical data of our patients including serum alanine transferase (ALT) and HCV viral load were also recorded.Briefly, Eighteen patients with chronic HCV infection and 18 healthy blood donors were enrolled in our study. PBMCs were isolated and incubated in 3-5 106/ mL RPMI-1640 medium containing 10% fetal bovine serum. After 2 hours incubation at 37 in 5% CO2 atmosphere, non-adherent cells were removed by gently rinsing with PBS. The adherent cells were then induced to proliferate and differentiate in complete fresh RPMI 1640 medium containing 1000 U/mL GM-CSF and 1000 U/mL IL-4. TNF- (1000 U/mL ) was added into the culture medium at 5th day. We compared DC1 from both patients and healthy people and found DC1 from patients had a lower yield than in healthy donors, which suggests that there may be a functional defectof DC1 in HCV-infected patients.Our data showed that fluorescence density of CD80, CD86, CDla and HLA-DR expression on DC1 was significantly lower in patients with chronic HCV infection than those in normal controls ( 14.82 13.32% vs 76.46 12.25%, 18.68 13.76% vs 84.38 9.72%, 6.33 4.98% vs 89.56 8.96%, 29.14 14.00% vs 92.47 9.34%, respectively, all p<0.001 ) . Our results showed both yield of DC1 production and expression level of phenotypic molecules significantly decreased in patients with chronic HCV infection. The result suggests the defective function of DC1 may be, at least, due to HCV RNA replication.We also found there were a significant increase in ratio and numbers of circulating CD4+ T Lymphocyte subsets, but a decrease in ratio and numbers of CD8+ T cells and NK cells, which produces a increased CD4/CD8 ratio in patient group compared with those in normal controls (all p<0.01 ) . In addition, we found a negative association of HCV RNA level with DC1 numbers as well as the serum ALT level and DC1numbers in these patients. The result may partly reflect the weakness of HCV-specific cytotoxic lymphocyte (CTL) reaction and lead to the inability to control the in vivo HCV replication.Furthermore, we analyzed three of 18 patients before and after IFN- mono-therapy and found that the peripheral DC1 production increased, but ALT level and viral load significantly decreased in HCV patients after the 6 month of IFN- treatment. These results indicate that both DC1 production and function could be restored when the HCV replication was inhibited.In conclusion, mature DC1 from PBMC of HCV patients could be induced by cytokine cocktail in vitro, but the function of DC1 was significantly more defective in patients with chronic HCV infection than in healthy donors, which may contribute to viral evasion of host adaptive immunity. The lower peripheral CD8+ T cells and NK cells may present the decreased antiviral adaptive response in HCV patients. Our findings would help us not only get more insight of thepathogenesis of chronic HCV infection, but also to establish a more reasonable therapeutic regimen for HCV patients in the future.
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