180 Chapter 8 Antigen presentation Phagocytosis Immunosenescence Age Trophic support Blood-BrainBarrier Permeability for remyelination Synaptic pruning Self-renewal Apoptosis Cytokine and chemokine production Microglial functions Figure 1. Microglial functions in the central nervous system. Microglia have many immunological functions in the central nervous system by presenting antigens, secreting cytokines and chemokines and by phagocytosing myelin debris or dead cells. Microglia also self-renew the microglia pool through coordinated proliferation and apoptosis. During development, microglia are important for neuronal development by synaptic pruning. Microglia provide trophic support for maintaining myelin integrity as well as remyelination. During ageing microglia adopt a more proinflammatory profile. Microglia also play a role in maintaining and influencing the permeability of the blood–brain barrier. Frequently used markers to detect homeostatic or activated microglia are the ionized calcium binding adapter molecule 1 (IBA1), MHC class II cell surface receptor human leukocyte antigen DR (HLA-DR), CX3CR1 (fractalkine receptor), and cluster of differentiation (CD) markers, CD68, CD40, CD206, CD163, and CD11b18-20. However, these proteins are not unique to microglia as other macrophage populations, such as infiltrating monocyte-derived macrophages present during neuroinflammation and CNS-associated macrophages (CAMs), have also been reported to express these markers21-24. In addition, combinations of markers, such as
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