CD4 and infection: Because high levels of TGFβ proteins were present in the brain by 3 days after infection and continued to increase coincident with the infiltration of inflammatory cells into the CNS, we used flow cytometry to assess TGFb1 production by ILCs that infiltrate the brain early after infection [25] (Figure 2) as well as by CD4+ and CD8+ T cells, which accumulate later (Figure 3).