CCR4 and adult T-cell leukemia/lymphoma: C–C chemokine receptor type 4 (CCR4), also known as CD194, is expressed by several normal T-cell populations including regulatory T-cells (Tregs), Th2, and Th17 cells, and overexpressed on malignant T-cell subsets of patients with PTCL, CTCL and ATLL [98,99].