PlGF increases monocyte chemotaxis. Total leukocytes from fresh peripheral blood obtained after hypotonic lysis of RBCs were placed in a Boyden chamber against no chemical gradient (white bars, control) or a PlGF gradient of 1 nM (striped bars) or 5 nM (black bars). Lipopolysaccharide (LPS, gray bars) gradient was the positive control, which promotes neutrophil transmigration. Cells that transmigrated across 3 μm pore filters were stained and the total leukocytes counted in 9 fields (A) and a differential count obtained on the transmigrating neutrophils (B) or monocytes (C). Each bar represents mean ± SD (n = 3), and values that were statistically significant from controls are represented with an asterisk: *P < .05 and **P < .01.