Localized CCR2 Activation in the Bone Marrow Niche Mobilizes Monocytes by Desensitizing CXCR4
Fig 6
Proposed model: monocyte egress by CCR2-mediated cross-desensitization of CXCR4.
Monocytes in the bone marrow co-express CXCR4 and CCR2. These cells are juxtaposed to bone marrow-resident cells, which express their respective ligands, CXCL12 and CCL2. (A) Under normal conditions, monocytes are retained by CXCR4 signaling, which is activated by constitutively secreted CXCL12. CCR2 on these monocytes is not active as its ligand CCL2 is stored but not released. (B) During inflammation, stored CCL2 is rapidly released and activates CCR2, which desensitizes CXCR4 and promotes cell migration.