CD4 and B-cell chronic lymphocytic leukemia: The use of HLA-DR in the staining further identified groups of CD8+ and CD4+ effector memory T cells that increased between CLL time point 1 and 2 with the CD4+ cluster being specifically enriched for PD-1 (Fig. 2f, g and Supplementary Fig. 5), similar to that reported by Elston et al.15.