Expression pattern of microRNA-155 (miR-155) in serum and peripheral blood mononuclear cells (PBMCs) of genotype 4 (GT4)-hepatits C virus (HCV)-infected patients and healthy controls. miR-155 expression was quantified in PBMCs and serum of GT4-HCV-infected patients (n=15) and healthy controls (n=12), and in liver tissue samples of GT4-HCV-infected patients (n=10) and healthy controls (n=10). Expression of miR-155, as represented in relative quantitation (RQ), did not differ between patients and healthy controls (A) at the level of PBMCs (P=0.5715) or (B) at the level of the serum (P=0.8747). (C) In chronic HCV-infected liver tissues, miR-155 expression was significantly downregulated compared to healthy controls (*P=0.0301). Results are expressed as mean of relative quantitation ± standard error of the mean. ns, not significant.