Human placenta growth factor-1 (PLGF-1, PLGF) binds to the receptor FLT1/VEGFR-1. It acts as a potent chemoattractant for monocytes and only as a very weak mitogen for some endothelial cell types. The physiological function in vivo is still controversial. In several reports it was shown not to be a potent mitogen for endothelial cells and not angiogenic in vivo by using different assays. It was shown that PLGF from cell culture supernatants was angiogenic in the CAM assay and in the rabbit cornea assay.