Several chemokines, belonging to both the CXC and CC classes, act as positive or negative regulators of angiogenesis. We sought to investigate the role of CXCL13, B cell-attracting chemokine 1 (BCA-1), also known as B-lymphocyte chemoattractant (BLC), on endothelial cell functions. We tested the effect of CXCL13 on HUVEC chemotaxis and proliferation in the presence of fibroblast growth factor (FGF)-2 and found that such chemokine inhibits FGF-2-induced functions, while is not active by itself. To test whether other FGF-2-mediated biological activities may be affected, we evaluated the ability of CXCL13 to rescue HUVEC from starvation-induced apoptosis, as FGF-2 is a survival factor for endothelial cells, and found that CXCL13 partially inhibits such rescue. Multiple mechanisms may be responsible for these biological activities as CXCL13 displaces FGF-2 binding to endothelial cells, inhibits FGF-2 homodimerization, and induces the formation of CXCL13-FGF-2 heterodimers. Our data suggest that CXCL13 may modulate angiogenesis by interfering with FGF-2 activity. (C) 2001 Academic Press.