Granzyme K‐deficient mice show no evidence of impaired antiviral immunity

The biological role of granzyme K, a serine protease of cytotoxic T lymphocytes (CTL), is controversial. It has been reported to induce perforin‐mediated cell death in vitro , but is also reported to be non‐cytotoxic and to operate in inflammatory processes. To elucidate the biological role of this protease, we have deleted the granzyme K gene in mice (mutant allele: Gzmk tm1.1Pib ; MGI:5636646). Gzmk −/− mice are healthy, anatomically normal, fecund and show normal hematopoietic development. Gzmk −/− mice readily recover from lymphocytic choriomeningitis virus and mouse pox Ectromelia virus infection. Ex vivo , virus‐specific granzyme K‐deficient CTL are indistinguishable from those of wild‐type mice in apoptosis induction of target cells. These data suggest that granzyme K does not play an essential role in viral immunity or cytotoxicity. Our granzyme K knockout line completes the collection of mouse models for the human granzymes, and will further our understanding of their biological roles and relationships.