Neutrophil-activating protein 3 (NAP3) also known as chemokine (C-X-C motif) ligand 1 (CXCL1) is a small cytokine belonging to the CXC chemokine family. NAP3 is expressed by macrophages, neutrophils and epithelial cells,and has neutrophil chemoattractant activity. Thus, chemotaxis assay used 24-well microchemotaxis system was undertaken to detect the chemotactic effect of NAP3 on THP-1 the human monocytic cell line. Briefly, THP-1 cells were seeded into the upper chambers (150 ul cell suspension,106 cells/ml in RPMI 1640 with FBS free) and different concentrations of recombinant mouse NAP3 diluted with serum free RPMI 1640 was added in lower chamber with a polycarbonate filter (8 um pore size) used to separate the two compartments. After incubation at 37 ℃ with 5% CO2 for 1h, the filter was removed, then cells in low chamber were observed by inverted microscope at low magnification (×100) and the number of migrated cells were counted at high magnification(×400) randomly (five fields for each filter). Result shows recombinant mouse NAP3 is able to induce migration of THP-1 cells. The migrated THP-1 cells in low chamber at low magnification (×100) were shown in Figure 1. Statistical results were shown in Figure 2. The optimum chemotaxis of NAP3 occurs at 0.001 ng/ml.

Figure 2. The chemotactic effect of NAP3 on THP-1 cells