Chemotactic activity of PF-4 variants for immature DCs. CXCL4L1 and CXCL4 were tested for their ability to induce chemotaxis of human immature DCs derived from peripheral blood in the Boyden microchamber (A). * (P < .05) indicates statistically significant migration toward chemokine (Mann Whitney test). The chemotactic response of CXCL4 (100 ng/mL), CXCL4L1 (100 ng/mL), and CCL3 (100 ng/mL) was reduced after treatment with 3 μg/mL pertussis toxin (Ptox; B) as determined by the Mann Whitney test (*P < .05; **P < .005). Results represent the mean ± SD of migrated cells of 4 (A) or 3 (B) independent experiments.