Microglia

The first observation of the dynamic nature of microglia, in particular of their potential to change morphology following an insult, has begun over one century ago, in 1919, when Pío del Río Hortega characterized and described the immune cells in the brain parenchyma. Driven by the growing interest in microglia, since then, enormous scientific advances have been made specifically on how they subtly respond to environmental stimuli by moving among different phenotypes. Although the great amount of studies in the field, however, microglia and their signaling remain enigmatic, and the study of the mechanisms through which different biological environments produce different microglia phenotypes (phenotypic plasticity) as well as the dynamics of microglia–neuron communication in health and disease has attracted great attention in the field of neurobiology. The 9 articles included in this special issue of Seminars in Cell and Developmental Biology reflect the wide scope of current research and provide a compelling review of the possible mechanisms/factors that control microglia identity and function in health and disease. All articles highlight the dynamic role that microglia play within the CNS for maintaining and restoring the homeostatic environment for an efficient cell-to-cell communication. The striking morphology of microglia is functional for this purpose, and their ramifications constantly survey the microenvironment and allow these cells to detect any homeostatic change.