Recent studies suggest that the evolution of viral infections and chronic inflammation in NAFLD are deeply influenced by CD4+ T helper cells expressing IL-17 , defined as T helper 17 (Th17) cells. Broadening the knowledge on the role of diet in the course of NAFLD and HCV infection in the activation of Th17 cells and in the alteration of some of their functions, will allow to shed light on the pathogenic mechanisms underlying the progression of immune-mediated diseases. Moreover, this investigation will allow to understand whether Th17 cells may have a role in the diminished response to therapy in patients who have high cholesterol levels.