Indeed, a study by Javan et al. reported the downregulation of PD-1/PD-L1 in PBMCs of relapsing RRMS patients, highlighting the dualistic role of PD-1/PD-L1 co-stimulatory signalling in different stages of RRMS. The gene discussed is PDCD1; the disease is relapsing-remitting multiple sclerosis.