Interestingly, another study of adult kidney transplant recipients immunophenotype have shown an association between increased PD-1 expression by CD8+ T cells and increased risk of graft rejection [47], authors of that study conclude that increased PD-1 expression might result from chronic immuneactivation; which is also in line with our hypothesis of chronic allogeneic stimulation. The gene discussed is CD8A; the disease is kidney transplant.