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Mediators of Inflammation
Volume 2015, Article ID 816460, 16 pages
http://dx.doi.org/10.1155/2015/816460
Review Article

Understanding the Mysterious M2 Macrophage through Activation Markers and Effector Mechanisms

Institute for Comparative Molecular Endocrinology, Center of Biomedical Research, University of Ulm, Helmholtzstrasse 8/1, 89081 Ulm, Germany

Received 12 February 2015; Accepted 30 April 2015

Academic Editor: Yona Keisari

Copyright © 2015 Tamás Rőszer. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The alternatively activated or M2 macrophages are immune cells with high phenotypic heterogeneity and are governing functions at the interface of immunity, tissue homeostasis, metabolism, and endocrine signaling. Today the M2 macrophages are identified based on the expression pattern of a set of M2 markers. These markers are transmembrane glycoproteins, scavenger receptors, enzymes, growth factors, hormones, cytokines, and cytokine receptors with diverse and often yet unexplored functions. This review discusses whether these M2 markers can be reliably used to identify M2 macrophages and define their functional subdivisions. Also, it provides an update on the novel signals of the tissue environment and the neuroendocrine system which shape the M2 activation. The possible evolutionary roots of the M2 macrophage functions are also discussed.