IFNG and infection: Given the known differences in the timing of IFNγ production in response to N. caninum infection (13) as well as the significantly higher frequency of peritoneal IFNγ+ cells 4 h post-infection in N. caninum-infected mice compared to those infected with T. gondii (Fig. 6B), we used a follow-up experiment to quantify the numbers of IFNγ+ NK cells in peritoneal and spleen cells from mice infected with each species.