Multiple studies have found that the individual loss of either GzmA or GzmB has no effect on the immune response to bacterial and viral infections,8 although perforin is clearly important for protection against various viral infections,11 and even a few bacterial pathogens.12, 13 Interestingly, extracellular levels of GzmA and GzmB were found to be increased in blood of humans infected with Salmonella enterica serovar Typhi.14 This evidence concerns the gene PRF1 and viral infectious disease.