Fatigue sensation often occurs in patients receiving IFN-α for treatment for hepatitis C. Loftis et al. [36] reported that the depressive symptoms correlate with elevated plasma levels of IL-1β and TNF-α in patients with chronic hepatitis C. Also, Kaneko et al. [37] reported that IL-1β-immunopositive cells are increased in the dentate gyrus in animals receiving subchronic i.p. injection of IFN-α. The gene discussed is IL1B; the disease is hepatitis C virus infection.