Natural killer (NK) cells play a crucial role in the initial host defense against pathogens such
as murine cytomegalovirus (MCMV). They respond rapidly and effectively control pathogen
replication while the adaptive immune system is being activated. However, in the absence of
an adaptive immune system, an effective initial NK cell response is not sufficient for long-
term pathogen control as demonstrated by the late recrudescence of disease and mortality
in immunodeficient mice infected with MCMV. In this setting, NK cells suppress the initial …