New advances on glial activation in health and disease

Table 1 Immunological molecules expressed in astrocytes and associated conditions

Immunological molecules	Effects	Conditions
Class II MHC	Autoimmune reactions	MS
ICAM-1, VCAM-1	Increased expression of pro-inflammatory cytokines	MS, AD
B7 (B7-1, B7-2)	T cell activation and differentiation	EAE
CD40	Promotes production of cytokines, chemokines, and neurotoxins	MS
CD1 (CD1b)	Antigen presentation to specialized T-cells	MS

MHC: Major immunohistocompatibility complex; ICAM: Intercellular adhesion molecule; VCAM: Vascular cell adhesion molecule; CD: Cluster of differentiation; MS: Multiple sclerosis; AD: Alzheimer’s disease; EAE: Experimental autoimmune encephalitis.

Table 2 Immune function of astrocytes

Pattern recognition receptors (expressed in astrocytes)	Effects	Conditions
TLRs (TLR2, TLR3, TLR4, TLR5, TLR9)	Upregulation cytokine/chemokine expression, induction of costimulatory molecules	Viral and bacterial infection, DAMPs
NOD receptors (NOD1, NOD2)	Upregulation of pro-inflammatory cytokines through NF-κB	Bacterial CNS infections
Scavenger receptors (SR-BI, SR-MARCO, RAGE, SRCL)	Mediates adhesion/uptake of A-beta in the CNS	AD
Mannose receptors (expressed)	Receptor-mediated endocytosis, CD4 independent HIV-1 entry	HIV
Complement factors (C1q, C4, C2, C3, C3d, C5, C5b-9, C6, C8)	CNS inflammation, cell activation and astrogliosis	TBI, synaptic plasticity, Pick’s disease, MS
Complement receptors (CR1, CR2, C3aR, C5aR)	CNS inflammation, cell activation and astrogliosis	TBI, synaptic plasticity

TLR: Toll-like receptor; NOD: Nucleotide-oligomerization domain; SR: Scavenger receptor; RAGE: Receptor for advanced glycation end products; DAMP: Damage-associated molecular pattern; TBI: Traumatic brain injury; CNS: Central nervous system; SR-BI: Scavenger receptor class B type I; SR-MARCO: Scavenger receptor - macrophage receptor with collagenous structure; SRCL: Scavenger receptor C-type lectin; CR1: Complement receptor type 1; CR2: Complement receptor type 2; C3aR: Complement component 3a receptor; C5aR: Complement component 5a receptor; NF-kappaB: Nuclear factor kappa-light-chain enhancer of activated B cells; AD: Alzheimer’s disease; HIV: Human immunedeficiency virus; MS: Multiple sclerosis.

Table 3 Mediators of astroglial function

Mediators	Examples	Effects on astroglial function
Cytokines	IL-6, IFNβ, TNF-α, TGF-β, GM-CSF, BAFF, IL-1β, MCP-1, RANTES	Increase BBB permeability, astrocyte activation, endothelial cell activation, microglial and monocyte activation, differentiation and proliferation, immunosuppression, release of neuroprotective mediators
Chemokines	CCL2, CCL5, CCL20, CXCL10, CXCL1, CXCl1, CXCl2, CX3CL1	Recruitment of monocytes and macrophages, dendritic T cells, T and B lymphocytes, and neutrophils/regulation of myelination and microglial activity, astrocyte proliferation and survival, migration of microglia and neural progenitors
Trophic Factors	EGF, FGF, NGF, BDNF, VEGF, IGF1	Astrocyte activation and morphological modification, neuronal/astrocytic survival, differentiation, function, and regeneration, oligodendrocyte survival, remyelination, neurogenesis
Endothelins	Et1, Et3	Inhibit gap junction coupling, disrupts direct intercellular communication in astrocytes, intracellular and extracellular ion homeostasis, metabolic trafficking, cellular swelling

IL: Interleukin; IFN: Interferon; TNF: Tumor necrosis factor; TGF: Transforming growth factor; GM-CSF: Granulocyte-macrophage colony-stimulating factor; BAFF: B-cell activating factor; MCP: Monocyte chemoattractant protein; CCL: Chemokine ligand; CXCL: CXC motif ligand; EGF; Epidermal growth factor; FGF: Fibroblast growth factor; NGF: Nerve growth factor; BDNF: Bone derived neurotrophic factor; VEGF: Vascular endothelial growth factor; IGF: Insulin-like growth factor; Et: Endothelin.