Moreover, in the present study, PD-1 expression was substantially upregulated in the effector memory CD8+ T cells of ABC-fed B*57:01-Tg mice as well as their CD4+ T cell-depleted counterparts (Fig. 2); this might suppress the induction of skin rash often associated with clinical AHS. The gene discussed is CD8A; the disease is mitochondrial DNA depletion syndrome 4a.