PDCD1 and infection: Consistent with the notion that PD-1-expressing cells are predominantly LCMV-specific in the context of chronic LCMV infection, we also confirmed a similar differentiation pattern of LCMV tetramer-positive CD8+ T cells to PD-1+ CD8+ T cells in the spleen at 7 days post-infection (dpi) (Supplementary Fig. 3).