CCL2 and escherichia coli infection: To explore the role of specific immune pathways in the vascular changes associated with infection, we applied the E. coli infection paradigm to mice with null mutations in (1) Tlr4, the gene coding for the innate immune system’s LPS receptor, or (2) Ccr2, the gene coding for one of the receptors for monocyte chemoattractant protein-1 (MCP1/CCL2), a chemokine that recruits immune cells to sites of infection (Figure 7).