CCL2 and bacterial infectious disease: We found that resident macrophages were also the first-responders in bacterial infections wherein overall myeloid cell recruitment is dependent on Toll-like receptor (TLR-MyD88) signaling rather than the CCL2-CCR2 axis (Cambier et al., 2014b), such as in the case of PDIM-deficient Mm (ΔmmpL7) and the mucosal commensal-pathogens Staphylococcus aureus and Pseudomonas aeruginosa (Figures 1F–1H).