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Tanaka. Neuroimmunol Neuroinflammation 2020;7:73-91 Neuroimmunology
DOI: 10.20517/2347-8659.2020.04 and Neuroinflammation

Review Open Access

Favorable and unfavorable roles of microglia and
macrophages in the pathologic central nervous

system

Junya Tanaka

Department of Molecular and Cellular Physiology, Graduate School of Medicine, Ehime University, Toon, Ehime 791-0295,
Japan.

Correspondence to: Prof. Junya Tanaka, Department of Molecular and Cellular Physiology, Ehime University, School of Medicine,
Toon, Ehime 791-0295, Japan. E-mail: jtanaka@m.ehime-u.ac.jp

How to cite this article: Tanaka J. Favorable and unfavorable roles of microglia and macrophages in the pathologic central nervous
system. Neuroimmunol Neuroinflammation 2020;7:73-91. http://dx.doi.org/10.20517/2347-8659.2020.04
Received: 8 Jan 2020 First Decision: 14 Feb 2020 Revised: 21 Feb 2020 Accepted: 12 Mar 2020 Available online: 10 Apr 2020

Science Editor: Jeffrey Bajramovic Copy Editor: Jing-Wen Zhang Production Editor: Jing Yu

Abstract

Resident microglia in the central nervous system (CNS) are activated rapidly in response to even minor pathologic
changes in the CNS, releasing various cytokines, growth factors, reactive oxygen species and other bioactive
substances, in addition to eliminating synapses and degenerating cells through phagocytosis. Monocytes in
circulation invade the inflamed brain tissues and develop into macrophages that also produce several bioactive
substances and engage in phagocytosis. This article introduces methods for distinguishing microglia and
macrophages. The pathophysiological roles of resident microglia and macrophages are discussed in animal models
with neuroinflammation in the brain either with or without disruption of the blood-brain barrier. Both cell types have
ameliorating and aggravating effects on the pathologic CNS, and their different roles are addressed in this article.
Furthermore, this article compares the effects of some pharmacological interventions to induce phenotypic cellular
changes for improved outcomes of the pathologic CNS.

Keywords: Parkinson’s disease, stroke, traumatic brain injury, axotomy, spinal cord, glucocorticoid, noradrenaline,
bromovalerylurea

INTRODUCTION
Microglia and blood-borne macrophages play major roles in the pathophysiological processes in various
kinds of pathologies of the central nervous system (CNS) by releasing numerous bioactive substances,

© The Author(s) 2020. Open Access This article is licensed under a Creative Commons Attribution 4.0
International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
sharing, adaptation, distribution and reproduction in any medium or format, for any purpose, even commercially, as long
as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
and indicate if changes were made.

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