Objective: To investigate the changes of total natural killer (NK) cell number and its subset proportions and the expression levels of activation factor CD100 on NK cells in chronically hepatitis C virus (HCV) infected patients before and after initiation of antiviral treatment.
Methods: The frequencies of total NK cells and their subsets as well as CD100 expression on NK cells in HCV infected patients were detected by flow cytometry. The level of soluble CD100 (sCD100) in serum was measured by ELISA. The correlations of CD100 with alanine aminotransferase (ALT) and HCV-RNA were analyzed using Spearman correlation test.
Results: The proportion of CD56(dim) NK cell subset decreased, whereas CD56(neg) subset increased in chronic HCV infected patients as compared with healthy controls (P<0.05). The proportion of CD56(bright) NK cells was elevated and that of CD56(neg) NK subsets was reduced in HCV infected patients with early virological response (EVR) (P<0.05); however, total NK cells and their subsets returned to the normal in patients with sustained virological response (SVR) after the initiation of antiviral treatment. We also observed that sCD100 level declined significantly (P<0.05), whereas CD100 expression on NK cells slightly decreased as compared with healthy controls, but the difference was not statistically significant. The levels of sCD100 and CD100 expression on NK cells were markedly up-regulated in EVR patients (P<0.05) and dropped to the normal in SVR patients. Spearman correlation analysis showed that CD100 expression was positively related to ALT level and negatively associated with HCV-RNA titer in HCV infected patients (P<0.05).
Conclusion: Decreased CD100 expression may be associated with viral persistence. As one of immune molecules regulated by IFN-α, CD100 seems to be involved in HCV clearance by NK cells.