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Review Article

Exp Neurobiol 2013; 22(2): 59-67

Published online June 30, 2013

© The Korean Society for Brain and Neural Sciences

Brain Inflammation and Microglia: Facts and Misconceptions

Hey-Kyeong Jeong1,2,3,4, Kyungmin Ji1,2,3,4, Kyungjin Min1,2,3,4 and Eun-Hye Joe1,2,3,4*

1Neuroscience Graduate Program, Department of Biomedical Sciences, 2Department of Pharmacology, 3Chronic Inflammatory Disease Research Center, 4National Research Lab of Brain Inflammation, Ajou University School of Medicine, Suwon 442-721, Korea

Correspondence to: *To whom correspondence should be addressed.
TEL: 82-31-219-5062, FAX: 82-31-219-5069


The inflammation that accompanies acute injury has dual functions: bactericidal action and repair. Bactericidal functions protect damaged tissue from infection, and repair functions are initiated to aid in the recovery of damaged tissue. Brain injury is somewhat different from injuries in other tissues in two respects. First, many cases of brain injury are not accompanied by infection: there is no chance of pathogens to enter in ischemia or even in traumatic injury if the skull is intact. Second, neurons are rarely regenerated once damaged. This raises the question of whether bactericidal inflammation really occurs in the injured brain; if so, how is this type of inflammation controlled? Many brain inflammation studies have been conducted using cultured microglia (brain macrophages). Even where animal models have been used, the behavior of microglia and neurons has typically been analyzed at or after the time of neuronal death, a time window that excludes the inflammatory response, which begins immediately after the injury. Therefore, to understand the patterns and roles of brain inflammation in the injured brain, it is necessary to analyze the behavior of all cell types in the injured brain immediately after the onset of injury. Based on our experience with both in vitro and in vivo experimental models of brain inflammation, we concluded that not only microglia, but also astrocytes, blood inflammatory cells, and even neurons participate and/or regulate brain inflammation in the injured brain. Furthermore, brain inflammation played by these cells protects neurons and repairs damaged microenvironment but not induces neuronal damage.

Keywords: brain inflammation, microglia, repair