Monocyte Chemotactic Protein 1 (MCP1), also known as C-C motif chemokine 2(CCL2), is a member of the β (C-C) subfamily of chemokines that is a chemoattractant for monocytes and basophils. Rat CCL2 is secreted as a 14 kDa glycoprotein monomer but noncovalent dimers probably occur. CCL2 is best known as a chemotactic agent for mononuclear cells. Thus, chemotaxis assay used 24-well microchemotaxis system was undertaken to detect the chemotactic effect of recombinant rat MCP1 on the THP-1 cell line. Briefly, THP-1 cells were seeded into the upper chambers (150 μL cell suspension, 106 cells/mL in RPMI 1640 with FBS free) and MCP1 (0.01 ng/mL, 0.1 ng/mL, 1 ng/mL, 10 ng/mL,100 ng/mL and 1000 ng/mL diluted separately in serum free RPMI 1640 ) was added in lower chamber with a polycarbonate filter (8 μm pore size) used to separate the two compartments. After incubation at 37 ℃ with 5% CO2 for 2h, 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 MCP1 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 results were shown in Figure 2. The optimum chemotaxis of recombinant rat MCP1 occurs at 0.01-0.1 ng/mL.

Figure 2. The chemotactic effect of recombinant rat MCP1 on THP-1cells