PDCD1 and diffuse large B-cell lymphoma: In chronic diseases, compared to EBV−DLBCL, EBV+ DLBCL showed that both CD4+ and CD8+ T cells demonstrated elevated PD-1 expression.There was also a significant decline in CD28+ KLRG1−and CD28+ CD57−KLRG1−subsets among CD8+ T cells in EBV+ patients (18).