ICOS and synovial sarcoma: Specifically for cutaneous T-cell lymphoma, when Phillips et al. developed and applied a 56-marker CODEX antibody panel to eight cutaneous T-cell lymphoma samples, they found that ICOS was strongly expressed on CD4+ T cells and Tregs [38], while Geskin et al. observed that Tregs from patients with SS markedly suppressed proliferation of autologous CD4+CD25- responder T cells [39].