Seeing is believing: Visualizing immune cells and calcium signals at different stages of neuroinflammation

Abstract

Multiple sclerosis (MS) is a neuroinflammatory disease characterized by demyelination of neurons in the central nervous system (CNS) (1). While the ultimate cause of the disease is unknown, MS is commonly considered to be an autoimmune disorder in which autoreactive CD4+ T cells are activated by an (unknown) autoantigen presented by antigen-presenting cells (APCs) outside the CNS. Once in the CNS, T cells are activated by microglia-derived or CNS-infiltrating APC, resulting in inflammation and myelin damage. The main T cell subsets causing disease in MS are T helper (Th) 1 and Th17 cells, which produce the proinflammatory cytokines interferon gamma (IFN-γ), interleukin (IL)-17A, and granulocyte–macrophage colony-stimulating factor. Studies in MS patients have shown that IL-17A and IFN-γ levels are increased in T cells isolated from CNS lesions and the cerebrospinal fluid (2, 3). A similar role of Th1 and Th17 cells has been found in the experimental autoimmune encephalomyelitis (EAE) rodent model of MS. The proinflammatory function of Th1 and Th17 cells is kept in check by regulatory T (Treg) cells, a subset of CD4+ T cells that express the transcription factor Foxp3 by suppressing effector T cell functions and thus CNS inflammation. Treg cells attenuate the severity of EAE and contribute to recovery from CNS inflammation (4). A report by Othy et al. (5) sheds light on the spatiotemporal interaction of Th17 cells, Treg cells, and APCs and their migration at three different stages of EAE. It also shows how Treg cells modulate Ca2+ signals in Th17 cells in the spinal cord. For their studies, Othy et al. (5) developed Foxp3EGFP IL-17TdT reporter mice to express enhanced green fluorescent protein (EGFP) in Treg cells and TdTomato in Th17 cells, as well as Foxp3EGFP CD11cEYFP reporter mice. Using this fate-mapping approach, the … [↵][1]1To whom correspondence may be addressed. Email: feskes01{at}nyumc.org. [1]: #xref-corresp-1-1