Microglia in normal appearing white matter of multiple sclerosis are alerted but immunosuppressed. Issue 11 (6th September 2013)

• Record Type: Journal Article
• Authors: Melief, Jeroen; Schuurman, Karianne G.; van de, Martijn D. B.; Smolders, Joost; van, Marco; Hamann, Jörg; Huitinga, Inge
• Is Part Of: Glia. Volume 61:Issue 11(2013:Nov.)
• Page Start: 1848
• Page End: 1861
• Publication Date: 2013-09-06
• Subjects: Neuroglia -- Periodicals; Neurology -- Periodicals; 611.0188
• DOI: 10.1002/glia.22562
• Languages: English
• ISSNs: 0894-1491

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Little is known about the functional phenotype of microglia in normal appearing white matter (NAWM) of multiple sclerosis (MS), although it may hold valuable clues about mechanisms for lesion development. Therefore, we studied microglia from NAWM obtained post‐mortem from controls (<italic>n</italic> = 25) and MS patients (<italic>n</italic> = 21) for their phenotype <italic>ex vivo</italic> and their immune responsiveness <italic>in vitro</italic>, using a microglia isolation method that omits culture and adherence. By flow cytometry, microglia in MS NAWM displayed elevated CD45 levels and increased size and granularity but were distinct from autologous choroid plexus macrophages by absent or low expression of additional markers, in particular CD206. Flow cytometric analysis of microglia from NAWM of three controls and four MS patients showed alterations in levels of Fc‐gamma receptors in MS. In primary microglia from a bigger sample of subjects, analysis of Fc‐gamma receptors by quantitative PCR indicated a significant increase in mRNA levels of the inhibitory CD32b isoform in MS NAWM. Despite their changed activation status, microglia from MS NAWM were unresponsive to lipopolysaccharide <italic>in vitro</italic>. Notably, culture with dexamethasone led to an impaired induction of the inflammation‐limiting cytokine CCL18 in microglia from MS NAWM compared with those from control NAWM. Together, these data demonstrate that microglia in MS NAWM are in an alerted state, but display features of immunosuppression. Thus, the activation status of microglia in NAWM of MS patients likely reflects a response to ongoing neuroinflammation, which coincides with upregulation of immunoregulatory molecules to prevent full activation and damage to the vulnerable milieu. GLIA 2013;61:1848–1861</p> </abstract>