Myeloid Cells in the Central Nervous System

Abstract

The central nervous system (CNS) and its meningeal coverings accommodate a diverse myeloid compartment that includes parenchymal microglia and perivascular macrophages as well as choroid plexus and meningeal macrophages, dendritic cells, and granulocytes. These myeloid populations enjoy an intimate relationship with the CNS, playing an essential role in both health and disease. Although the importance of these cells is clearly recognized, their exact function in the CNS continues to be explored. Here we review the subsets of myeloid cells that inhabit the parenchyma, meninges, and choroid plexus, and discuss their roles in CNS homeostasis. We also discuss the role of these cells in various neurological pathologies, such as autoimmunity, mechanical injury, neurodegeneration, and infection. We highlight the neuroprotective nature of certain myeloid cells, emphasizing their therapeutic potential for the treatment of neurological conditions.

Neuroimmune Alterations in Autism: A Translational Analysis Focusing on the Animal Model of Autism Induced by Prenatal Exposure to Valproic Acid

“…Studies have shown that, although microglial cells play a major role in brain surveillance, perivascular macrophages represent a crucial immune regulator and sensor of perturbations in the CNS and periphery. These cells are derived from the bone marrow and are intimately associated with the bloodstream since they reside between EC and astrocyte end feet [72][73][74]. This privileged location of the perivascular macrophages allows them to simultaneously monitor the blood and the brain interstitial fluid, providing a fine control of brain homeostasis and BBB integrity [72,75].…”

“…In the physiological condition, studies have observed the presence of monocytes in meningeal spaces, although more evidence is still needed [82]. Granulocytes (i.e., neutrophils, mast cells, eosinophils, and basophils) can be found in meningeal spaces with mast cells also present in brain parenchyma [72,83]. These cells are highly phagocytic and play important roles in response to brain infections and tissue damage [72,84,85].…”

“…Granulocytes (i.e., neutrophils, mast cells, eosinophils, and basophils) can be found in meningeal spaces with mast cells also present in brain parenchyma [72,83]. These cells are highly phagocytic and play important roles in response to brain infections and tissue damage [72,84,85]. DC, the main antigen-presenting cells in the periphery, can also be found in the CNS.…”

Lymphatic clearance is the main drainage route of lamotrigine-loaded micelles following delivery to the brain

“…Meantime, nanoparticles can be drained from tissues by lymphatics and they can be phagocytosed by subcapsular macrophages which exist in the draining lymph nodes; this can then be presented to adaptive immune cells, such as T cells, to mount an immune response in the brain. Alternatively, meningeal macrophages might uptake nanoparticles and modulate the meningeal immune response …”

Cancer Immunotherapy Getting Brainy: Visualizing the Distinctive CNS Metastatic Niche to Illuminate Therapeutic Resistance

“…Microglia, which are considered the primary APC in the brain microenvironment, serve as tissue-resident macrophages and may adapt to become perivascular macrophages that aid in tumor proliferation, invasion, and angiogenesis to create a more favorable tumor microenvironment (TME) (9,10). It has been shown that microglia have the potential to differentiate into the M1-like or M2-like macrophages to induce a pro-inflammatory (TNFα/IFNγ response) or pro-tumoral (IL-4/TGFβ response) phenotype, respectively (11).…”