Intriguingly, higher expression of PD-1, another marker associated with T-cell exhaustion, along with loss of CD28, reflecting senescence, is also observed in both CD4+ and CD8+ T-cells in HAM/TSP and ATLL (Shimauchi et al., 2007; Saeed et al., 2020). The gene discussed is CD4; the disease is adult T-cell leukemia/lymphoma.