CD27 and infection: In line with the study of Ahn et al. [33], the percentage of PD-1+ MuV-specific T cells was associated with the differentiation status of the MuV-specific T cells, as we found a significant negative correlation with the percentage of both CM (CD27+, CD45RO+) and MPEC (KLRG-1−, CD127+) at 1.5 and 9 months post-MuV-infection (Figure S8).