CD4 and B-cell chronic lymphocytic leukemia: Moreover, CLL-associated CD4+ T-cells express higher levels of the inhibitory receptors programmed cell death protein 1 (PD-1) [6, 7, 9–11], CD160 [9], and T-cell immunoreceptor with Ig and ITIM domains (TIGIT) [8] as well as human leukocyte antigen (HLA)-DR as a marker of activation [6].