Monocyte and macrophage differentiation: circulation inflammatory monocyte as biomarker for inflammatory diseases

TLDR

Monocytes are highly plastic, heterogeneous cells that express diverse receptors and can differentiate into inflammatory or anti‑inflammatory subsets, rapidly recruited to tissues during damage or infection and serving as potential biomarkers for inflammatory diseases. The review aims to summarize current knowledge on monocyte heterogeneity and its impact on human disease. The authors describe the heterogeneity of human and murine monocytes, the functions of distinct subsets, and propose a mechanism for monocyte differentiation. Inflammatory monocyte subsets are valuable biomarkers for inflammatory diseases, including cardiovascular disease.

Abstract

Monocytes express various receptors, which monitor and sense environmental changes. Monocytes are highly plastic and heterogeneous, and change their functional phenotype in response to environmental stimulation. Evidence from murine and human studies has suggested that monocytosis can be an indicator of various inflammatory diseases. Monocytes can differentiate into inflammatory or anti-inflammatory subsets. Upon tissue damage or infection, monocytes are rapidly recruited to the tissue, where they can differentiate into tissue macrophages or dendritic cells. Given the rapid progress in monocyte research from broad spectrum of inflammatory diseases, there is a need to summarize our knowledge in monocyte heterogeneity and its impact in human disease. In this review, we describe the current understanding of heterogeneity of human and murine monocytes, the function of distinct subsets of monocytes, and a potential mechanism for monocyte differentiation. We emphasize that inflammatory monocyte subsets are valuable biomarkers for inflammatory diseases, including cardiovascular diseases.