Thus, besides the TRM cell markers these cells also expressed the inhibitory receptors PD-1 and CD223, and the ectonucleotidase CD39, which are all markers associated with T cell exhaustion (Barber et al., 2006; Blackburn et al., 2009; Gupta et al., 2015) and are known to be upregulated upon LCMV clone 13 infection. This evidence concerns the gene ENTPD1 and infection.