In transgenic mice, in which cells expressing the chemokine CCL2, also known as monocyte chemoattractant protein-1 (MCP1), a ligand of CCR2, were marked using a bacterial artificial chromosome (BAC) mediated transgenesis with a linked GFP, the MCP1-GFP expression was significantly increased in CD45-Ter119-CD31-Sca1-PDGFRβ+ cells after administration of low concentrations of LPS and after infection with Listeria monocytogenes. The gene discussed is CCL2; the disease is infection.