Mast cell activation and neutrophil recruitment promotes early and robust inflammation in the meninges in EAE

Area of Science:

• Neuroimmunology
• Central Nervous System (CNS) Inflammation
• Autoimmune Diseases

Background:

• The meninges, protective membranes of the brain and spinal cord, are increasingly recognized as active immune sites.
• The blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barrier are implicated as entry points for immune cells into the CNS in multiple sclerosis (MS).
• Previous studies indicated mast cells in the meninges exacerbate experimental autoimmune encephalomyelitis (EAE), an MS model, by promoting inflammatory cell infiltration.

Purpose of the Study:

• To investigate the mechanisms by which meningeal mast cells contribute to early inflammatory events in EAE.
• To identify the role of mast cells and neutrophils in the initial stages of CNS inflammation preceding disease onset.

Main Methods:

• Analysis of immune-associated gene expression in meninges during pre-clinical EAE.
• Assessment of mast cell activation and its effects on vascular integrity within 24 hours of disease induction.
• Investigation of mast cell-derived TNF in mediating neutrophil recruitment.

Main Results:

• Significant alterations in immune gene expression, including mast cell and neutrophil function markers, were observed in the meninges.
• Meningeal mast cells activated early (within 24 hours) but did not directly compromise CNS vascular integrity.
• Mast cell-produced TNF induced early meningeal neutrophil influx, which is known to affect vascular permeability.

Conclusions:

• Meningeal inflammation precedes CNS immune cell infiltration in EAE.
• Mast cells are early participants in disease initiation within the meninges.
• Mast cell-driven neutrophil recruitment and activation in the meninges likely promote early BBB and CSF-blood barrier breakdown, facilitating CNS immune cell entry.