Histidine 67 is critical for inhibiting the FGF2-induced capillary tube formation of HUVECs by CXCL4L1. (A) Representative images of HUVECs on Matrigel stimuled with FGF2 and in the presence or not of the indicated chemokine. (B) Quantitative analysis of the experiments shown in panel A obtained by counting the number of branching points from 4 fields.