IL5 and synovial sarcoma: As an aggressive CTCL, SS is a Th2-type disease, and it exhibits an exhaustion status of antitumor defense [15,19,20], with increased levels of interleukin (IL)-4, IL-5, and IL-13, and reduced levels of Th1 cytokines such as IL-2 and interferon (IFN)-γ, that reduce cell-mediated immunity [18,21].