CCL17 and classic Hodgkin lymphoma: The majority of T cells in cHL acquire immunosuppressive functions and their differentiation is shifted towards either THs or Tregs by tolerogenic cytokines (in particular, galectin-1, macrophage migration inhibitory factor, IL-7, CCL17/TARC, CCL22, CCL5, IL-4, IL-5, IL-10, and IL-13) secreted by tumor and non-tumor cells.