CD8+ T lymphocytes mediate immunosurveillance against persistent virus infections and virus-induced neoplasia and Moser et al. [39] demonstrated that the natural killer cell inhibitory receptor, CD94-NKG2A, is up-regulated by antiviral CD8+ T cells during acute polyoma infection and is responsible for down-regulating their antigen-specific cytotoxicity during both viral clearance and virus-induced oncogenesis. Here, KLRD1 is linked to viral infectious disease.