Two PD-1+CD8+ T cell subsets, stem-like (PD-1+CXCR5+TIM-3−) and terminally differentiated (exhausted; PD-1+CXCR5−TIM-3+), were sorted from the pooled splenocytes of chronically LCMV-infected mice (CD45.2+), and each CD8+ T cell subset was transferred into infection-matched mice (CD45.1+), followed by muPD1-IL2v therapy. Here, PDCD1 is linked to infection.