A transmembrane chemokine, CXC chemokine ligand 16, expressed by lymph node fibroblastic reticular cells has the potential to regulate T cell migration and adhesion

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Abstract
Stromal cells in lymphoid tissues provide microenvironmental fields required for the triggering of efficient immune responses. Fibroblastic reticular cells (FRCs) are one of the integral constituents of such stromal fields; they construct the reticular network and are considered to regulate immune cells' behavior. However, the factors that mediate the interaction between lymphocytes and FRCs are poorly understood. Here we show that a mouse lymph node (LN)-derived FRC cell line, BLS4, expresses a transmembrane chemokine, CXC chemokine ligand (CXCL) 16, in response to tumor necrosis factor α (TNFα) and IFNγ. TNFα-induced expression of CXCL16 depends on NFκB, p38 MAPK and PKA. Matrix metalloproteinase activity is required for producing soluble CXCL16 in the culture supernatant, likely via shedding at the juxtamembrane region of the extracellular domain. IL-12 enhances the expression of CXCR6 in anti-CD3/CD28-stimulated CD8+ T cells and their adhesion to the BLS4 cell surface in a TNFα-dependent fashion. The adherence is significantly inhibited in the presence of both anti-CXCL16 and anti-vascular cell adhesion molecule 1 (VCAM-1) antibodies. CXCL16 expression is also detected in the FRCs in LN sections and in gp38+VCAM-1+ FRCs isolated from LNs. Taken together, these findings suggest that CXCL16 is an important mediator of lymphocyte–stromal interaction within lymphoid tissues.