CXCL13 and angioimmunoblastic T-cell lymphoma: AITL originates from the neoplastic transformation of TFH cell, a subtype of T-CD4+ effector lymphocytes that reside in the germinal center and are characterized by high expression of the chemokine receptor CXCR5 (C-X-C motif receptor 5), chemokine CXCL-13 (C-X-C motif ligand 13), ICOS (CD28-related inducible T-cell co-stimulator), CD154, CD40L and NFATC1 (6, 33–36).