MCP-1 (monocyte chemoattractant protein 1), also known as CCL2 (C-C motif chemokine 2), is a small cytokine that belongs to the CC chemokine family. MCP-1 has been described as a chemoattractant for monocytes and proven to be able to induce chemotactic migration of THP-1 cells. Therefore, chemotaxis assay used 24-well microchemotaxis system was undertaken to detect the chemotactic effect of MCP-1 on the human monocytic cell line THP-1. Briefly, THP-1 cells were seeded into the upper chambers (100uL cell suspension, 106 cells/mL in RPMI 1640 with 0.5% FBS) and MCP-1 (25ng/mL and 50ng/mL diluted separately in serum free RPMI 1640) was added in lower chamber with a polycarbonate filter (8um pore size) used to separate the two compartments. After incubation at 37oC with 5% CO2 for 3h, 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).<br/>Result: MCP-1 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. Five fields of each chamber were randomly chosen, and the migrated cells were counted at high magnification (×400). Statistical result were shown in Figure 2. The optimum chemotactic concentration of MCP-1 is about 25ng/mL, which is in accordance with references.<br/>(A) THP-1 cells were seeded into the upper chambers and serum free RPMI 1640 with 50ng/mL MCP-1 was added in lower chamber, then cells in lower chamber were observed at low magnification (×100) after incubation for 3h; <br/>(B) THP-1 cells were seeded into the upper chambers and serum free RPMI 1640 with 25ng/mL MCP-1 was added in lower chamber, then cells in lower chamber were observed at low magnification (×100) after incubation for 3h;<br/>(C) THP-1 cells were seeded into the upper chambers and serum free RPMI 1640 without MCP-1 was added in lower chamber, then cells in lower chamber were observed at low magnification (×100) after incubation for 3h.<br/>Figure . The chemotactic effect of MCP-1 on THP1 cells.

Figure. The chemotactic effect of MCP-1 on THP-1 cells