PDCD1 and synovial sarcoma: More specifically, patients with SS had an expansion of circulating CXCR5+ICOS+PD-1+ activated Tfh-cells (figure 1D, E, online supplementary figure S2E, O) which displayed significantly increased IFN-γ, IL-21 and double IL-21/IFN-γ production in patients with SS compared with NSCS (figure 1F).