FKBP51s, a spliced isoform of 51 KDa FK506-binding protein (FKBP51), which is a cochaperone and plays a role in immunoregulation and basic cellular processes involved in protein folding and trafficking, was shown to physically interact with the naïve PD-L1 in the ER and catalyze PD-L1 folding, thus contribute to the glycosylation of PD-L1 in glioma as proposed by D'Arrigo et al. (225). The gene discussed is CD274; the disease is glioma.