Similarly to what has been observed for PD-1 expression on T cells, no association was found between PD-L1 levels on leukemic cells and other disease prognosticators [60], although its expression was further upregulated upon in vitro activation of CLL cells with proliferative stimuli such as CpG/IL-2 [58]. The gene discussed is PDCD1; the disease is B-cell chronic lymphocytic leukemia.