Non-Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock


Nr4a1-dependent Ly6C(low) monocytes monitor endothelial cells and orchestrate their disposal.


The functions of Nr4a1-dependent Ly6C(low) monocytes remain enigmatic. We show that they are enriched within capillaries and scavenge microparticles from their lumenal side in a steady state. In the kidney cortex, perturbation of homeostasis by a TLR7-dependent nucleic acid "danger" signal, which may signify viral infection or local cell death, triggers Galphai-dependent intravascular retention of Ly6C(low) monocytes by the endothelium. Then, monocytes recruit neutrophils in a TLR7-dependent manner to mediate focal necrosis of endothelial cells, whereas the monocytes remove cellular debris. Prevention of Ly6C(low) monocyte development, crawling, or retention in Nr4a1(-/-), Itgal(-/-), and Tlr7(host-/-BM+/+) and Cx3cr1(-/-) mice, respectively, abolished neutrophil recruitment and endothelial killing. Prevention of neutrophil recruitment in Tlr7(host+/+BM-/-) mice or by neutrophil depletion also abolished endothelial cell necrosis. Therefore, Ly6C(low) monocytes are intravascular housekeepers that orchestrate the necrosis by neutrophils of endothelial cells that signal a local threat sensed via TLR7 followed by the in situ phagocytosis of cellular debris.

Authors: Carlin LM, Stamatiades EG, Auffray C, Hanna RN, Glover L, Vizcay-Barrena G, Hedrick CC, Cook HT, Diebold S, Geissmann F
Journal: Cell; 2013 Apr 11; 153(2) 362-75. doi:10.1016/j.cell.2013.03.010
Year: 2013
PubMed: PMID: 23582326 (Go to PubMed)