Fig. 4: SCIMP can chemoattract the peripheral neutrophils both in vitro and in vivo.

a After separating human peripheral blood neutrophils (PBN), monocytes (PBM), and lymphocytes (PBL), the chemotactic activity of 1 nM IL-8, 1 nM SDF-1, and 1 mg/mL SCIMP-positive exosomes (SCIMP^exo) to these cells in vitro were measured using the TaxiScan system (n = 5). b, c The chemotaxis ability of the full-length SCIMP⁺ exosomes (1 mg/mL) and the extramembrane N-terminus truncated SCIMP⁺ exosomes (1 mg/mL) to human peripheral blood neutrophils in vitro were measured using the TaxiScan system (n = 5); SCIMP^- exosomes (1 mg/mL) acted as the control in (c). d The chemotactic activity of the purified full-length SCIMP protein (1 nM) and the SCIMP^N (1 nM) to human peripheral blood neutrophils in vitro were measured using the TaxiScan system (n = 5). e, f The pulmonary in situ chemotaxis activity of the murine SCIMP^N (10 μg in 50 μL PBS per mouse), vehicle buffer (PBS, 50 μL), murine SCIMP^exo (10 mg in 50 μL PBS per mouse), and the control exosomes, purified from CHO cells (10 mg in 50 μL PBS per mouse), was determined by measuring the percentage of neutrophils (Neu) in the BALF at 4 h post bronchial perfusion of these stimulators (n = 6). g, h After the mice were pretreated the mice with murine SCIMP^N (10 μg in 50 μL PBS per mouse), SCIMP-negative exosomes (10 mg in 50 μL PBS per mouse), or SCIMP-positive exosomes (10 mg in 50 μL PBS per mouse) via b.p for 2 h, the bacteria (E. coli) count in the BALF was measured at 4 h after the bacteria bronchial perfusion (1 × 10⁶ CFU per mouse, n = 6 in each group). i The activity of fMLF (1 nM), SCIMP^N (1 nM), SCIMP protein (1 nM), and SCIMP^exo (1 mg/mL) on the ROS release of human peripheral blood neutrophils was detected using cytometry at the time points of 1, 5, 10, 15, 20, 25 min after the stimulation (n = 2). The raw data is available in the “Source Data”.