Background& study aim: Natural killer (NK) cells are an integral part of the innate immune system. They have been suggestedto play an important role in both defense against viral hepatitis and the pathogenesis of other liver diseases. Our study aimsto investigating the expression of natural killer cells in viral hepatitis patients and if there is difference in those patients when compared with normal population

Patients & Methods: NK cell markers (CD3,CD56, and CD16) were studied by flowcytometery from96individuals including 76 patients with hepatitis B and C as well as 20 healthy subjects as control.

Results: Infection with viral hepatitis was associated with increased frequencies of CD3-&CD56+NK cells and CD3-&CD16+ NK cells in the peripheralblood; and severity of hepatitis is correlated with the percentage of NK cells in peripheral blood with no statistically significant difference between HCV and HBV infections.

Conclusion: NK cell phenotypic changes can equally be observed in HBVand HCVinfections andpercentage of NK cell differ with severity of hepatitis. So this study suggests that the alteration of NK cell phenotypeswith viral hepatitis depend ondisease activity rather than virus-specific factors.