To further define the phenotype associated with WNV-induced splenomegaly in IPS-1 2/2 mice, we also assessed the numbers of NK cells and neutrophils. Spleens from infected IPS-1 2/2 mice contained greater numbers of NK cells (CD4 2 CD8 2 NK1.1 + cells), NKT cells (CD4+/CD8+/NK1.1+ cells) and neutrophils (CD11b + Gr1 + cells) (Fig 7E) . Although WNVinfected wild type mice infected displayed slight increases in the absolute numbers of these specific cell types, a deficiency of IPS-1 resulted in a more marked enhancement of these immune cell populations.