Activation of PD-1 is relatively transient during infections, and at least one of its gene-promoter regulators is modified by FOXO1 as well as Nuclear Factor of Activated T cells-c1 (NFATc1), Signal Transducer and Activator of Transcription 1 (STAT1) and NFκB [104,105,106]. This evidence concerns the gene STAT1 and infection.