A Polecat’s View of Patrolling Monocytes

Abstract

A major obstacle to intravital visualization of inflammatory processes within large arteries is the motion of vessels that occurs near the beating heart. In this issue, Quintar et al. apply ILTIS, the German word for the European polecat that serves as an acronym for Intravital Live-cell Triggered Imaging System, to capture the most sophisticated images of inflammatory cell dynamics in the arterial vasculature to date, by timing data acquisition to a consistent point in every heartbeat. The authors show that patrolling nonclassical monocytes scan endothelium in plaque-prone areas, much as they have been described to elsewhere. The inability of these monocytes to patrol arteries leads to heightened endothelial damage within the artery. In this way, nonclassical monocytes safeguard against plaque development and progression.

Monocyte Dysfunction, Activation, and Inflammation After Long-Term Antiretroviral Therapy in an African Cohort

“…Low circulating nonclassical monocytes among ART-treated adults is likely due to continuous death of this phenotype, which is more permissive to HIV infection due to its high expression of CCR5. The nonclassical monocytes have high expression of CD16 + and FcγRIII and are known to have a unique ability of patrolling resting vasculature to remove debris and repair damaged tissue [10]. The low nonclassical monocytes exhibited by ART-treated HIV-infected adults without coinfections may play a role in the noncommunicable disease risk associated with chronic HIV disease [11].…”

Monocyte Recruitment, Specification, and Function in Atherosclerosis

“…They persist in vasculature by patrolling on the blood endothelial cells with crawling behavior dependent on LFA-1, CX3CR1, and CD36 [ 33 , 38 , 39 ]. Visualizing monocyte patrolling the endothelial surface through the use of intravital multiphoton microscopy, behavior has been a major advancement in the field [ 38 , 40 ]. Animals deficient in nonclassical monocytes, such as NR4A1 knockout mice [ 32 ], support the concept that nonclassical monocytes support endothelial health and maintenance [ 41 , 42 ].…”

Macrophage Biology, Classification, and Phenotype in Cardiovascular Disease

“…Functionally, classical and nonclassical monocytes possess unique qualities. Classical monocytes are typically associated with recruitment into tissues in response to insults, although they do circulate through tissues in the steady state (25), whereas nonclassical monocytes patrol the endothelium to promote vascular health (37–41). Even with the known roles of monocytes expanding, monocytes likely remain an important contributor of macrophage homeostasis in tissues.…”