CCL4 and B-cell chronic lymphocytic leukemia: Transfer of chronic lymphocytic leukemia (CLL)-derived exosomes or transmission of hY4, a non-coding Y RNA enriched in exosomes of CLL patient plasma, to monocytes can generate key CLL-associated phenotypes, including the release of cytokines CCL2, CCL4 and IL-6, and the expression of programmed cell death ligand 1 (PD-L1) [98].