Chemokine-scFv fusion proteins induce F-actin polymerization and chemotaxis. (A,B) F-actin polymerization in BALB/c peritoneal macrophages (A) or immature bone marrow–derived DCs (B) after stimulation with 10 ng/mL chemokine-fusion proteins. CD11b⁺ cells were incubated with the indicated MIP-1α and RANTES chemokine-fusion protein variants. At different time intervals, the cells were fixed with paraformaldehyde, stained with FITC-phalloidin, and analyzed by flow cytometry. Relative F-actin was calculated as the mean fluorescence relative to that of nonstimulated cells. (C,D) In vitro chemotaxis of the murine macrophage cell line P338D1 (C) or immature bone marrow–derived DCs (D) induced by RANTES- and MIP-1α-scFv fusion proteins. Chemotactic index (± SEM of triplicate samples), defined as fold increase in the number of migrating cells in the presence of fusion proteins over spontaneous migration, is presented. Recombinant human RANTES was used as control in panels A-D. (E) Recruitment of cells into the peritoneal cavity 18 hours after intraperitoneal injection of purified chemokine-scFv fusion proteins at a 1.5 μM (chemokine) concentration. Cells/mL in 10 mL lavage fluid is given. (F) Numbers of CD11c⁺ DCs in the peritoneal cavity 18 hours after intraperitoneal injection of chemokine-scFv fusion proteins.