Complement Receptor 2 is increased in cerebrospinal fluid of multiple sclerosis patients and regulates C3 function

Area of Science:

• Neuroimmunology
• Complement System Biology
• Neuroinflammation

Background:

• The complement system is crucial for immunity and brain synaptic plasticity.
• Soluble Complement Receptor 2 (sCR2) was previously identified in rodent nerve injury responses.
• The role of CR2 in human neuroinflammatory diseases like multiple sclerosis (MS) remains largely unexplored.

Purpose of the Study:

• To investigate the levels and significance of sCR2 in MS patients.
• To explore the molecular mechanisms of CR2 in complement C3 activation.
• To determine the potential role of CR2/sCR2 in neuroinflammation.

Main Methods:

• Quantification of sCR2 levels in cerebrospinal fluid (CSF) from MS patients (relapsing-remitting and secondary-progressive) and controls using ELISA.
• Correlation analysis of sCR2 levels with CSF complement components (C3, C1q) and disease severity measures.
• In vitro experiments to assess the effect of sCR2 on C3b cleavage to iC3b.

Main Results:

• Significantly elevated sCR2 levels were observed in CSF of MS patients compared to controls.
• CSF sCR2 levels positively correlated with CSF C3, C1q, and a disease severity measure.
• In vitro, sCR2 was found to inhibit the C3b to iC3b cleavage, modulating complement activation downstream of C3.

Conclusions:

• sCR2 is a potential biomarker for MS, with levels correlating to disease activity and complement component levels.
• sCR2 modulates complement activation by inhibiting C3b cleavage.
• These findings suggest a novel function for CR2/sCR2 in human neuroinflammatory conditions, particularly MS.