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Open Access Research

Complement activation in multiple sclerosis plaques: an immunohistochemical analysis

Gillian Ingram1, Sam Loveless2, Owain W Howell3, Svetlana Hakobyan2, Bethan Dancey2, Claire L Harris2, Neil P Robertson1, James W Neal2 and B Paul Morgan2*

Author Affiliations

1 Institute of Psychological Medicine and Clinical Neuroscience, Cardiff, UK

2 Institute of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, UK

3 Department of Neurology and Molecular Neuroscience, Institute of Life Sciences, Swansea University, Swansea, UK

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Acta Neuropathologica Communications 2014, 2:53  doi:10.1186/2051-5960-2-53

Published: 9 May 2014

Abstract

Introduction

Inflammation and complement activation are firmly implicated in the pathology of multiple sclerosis; however, the extent and nature of their involvement in specific pathological processes such as axonal damage, myelin loss and disease progression remains uncertain. This study aims to bring clarity to these questions.

Results

We describe a detailed immunohistochemical study to localise a strategically selected set of complement proteins, activation products and regulators in brain and spinal cord tissue of 17 patients with progressive multiple sclerosis and 16 control donors, including 9 with central nervous system disease. Active, chronic active and chronic inactive multiple sclerosis plaques (35 in total) and non-plaque areas were examined.

Multiple sclerosis plaques were consistently positive for complement proteins (C3, factor B, C1q), activation products (C3b, iC3b, C4d, terminal complement complex) and regulators (factor H, C1-inhibitor, clusterin), suggesting continuing local complement synthesis, activation and regulation despite the absence of other evidence of ongoing inflammation. Complement staining was most apparent in plaque and peri-plaque but also present in normal appearing white matter and cortical areas to a greater extent than in control tissue. C1q staining was present in all plaques suggesting a dominant role for the classical pathway. Cellular staining for complement components was largely restricted to reactive astrocytes, often adjacent to clusters of microglia in close apposition to complement opsonised myelin and damaged axons.

Conclusions

The findings demonstrate the ubiquity of complement involvement in multiple sclerosis, suggest a pathogenic role for complement contributing to cell, axon and myelin damage and make the case for targeting complement for multiple sclerosis monitoring and therapy.

Keywords:
Multiple sclerosis; Demyelination; Complement; Immunology; Histology; Immunohistochemistry