CD44 and infection: Indeed, while both the frequencies and absolute numbers of CD8+CD44+ T cells specific for GP33-41 and NP396-404 did not differ between IFNARfl/fl and IFNARfl/fl x Foxp3YFP-Cre mice on day 14 post-infection (Fig 1B and 1C), the production of the effector cytokines IFN-γ and TNF-α was markedly diminished (Fig 1E and 1F).