CCL2 acts on CXCR4-positive cells during inflammation in the bone marrow.

<p>(Inset) Transgenic reporter mice used in this study. 1) CCL2::CCL2-mRFP (CCL2 protein level reporter), 2) CCL2::mRFP (CCL2 transcriptional reporter), and 3) CCR2::CCR2-EGFP (CCR2 protein level reporter) (A-G) Bone marrow of CCL2::CCL2-mRFP; CCR2::CCR2-EGFP double transgenic mice. A differential interference contrast (A) and an overlaid fluorescent image (B) show CCL2-mRFP and CCR2-EGFP cells in close contact (arrows). (C-G) Under normal conditions, CCR2-EGFP mostly localizes to cell surface (green arrow). After LPS injection, most CCR2-EGFP cells are activated by CCL2, which is evident in granular CCR2-EGFP signals and endocytic vesicles containing both CCL2-mRFP and CCR2-EGFP (yellow arrow). (H-I) Bone marrow of CCL2::mRFP; CCR2::CCR2-EGFP double transgenic mice. After LPS injection, most CCR2-EGFP cells are activated by endogenous CCL2, which is evident in granular CCR2-EGFP (white arrow). Scale bars, 10 μm.