ICOS and neoplasm: Being a neoplasm of TFH-origin, AITL displays multiple TFH-related antigens, including PD-1/CD279 (programmed death-1), CD10 (a metalloendopeptidase called common acute lymphoblastic leukemia antigen/CALLA), BCL-6 (B-cell lymphoma 6 protein), CXCL-13 (C-X-C motif chemokine ligand 13), ICOS (inducible T-cell costimulator), SAP (signaling lymphocyte activation molecule [SLAM]-associated protein) and CXCR-5 (C-X-C motif chemokine receptor 5) (11, 35, 36, 77, 84, 85).