Ow MM, et al. - Researchers focused on a minority of injecting drug users who were resistant to hepatitis C (HCV) infection despite repeated low-dose exposures. They recognized rarity of exposure without infection following transfusion of HCV-contaminated blood. This suggested a high level of resistance to infection. In uninfected recipients, enhanced natural killer cell activation and killing, with weak HCV-specific T cell responses, were observed many years after exposure. This might contribute to protection from HCV acquisition, although additional protective factors were being searched in this important cohort.