Innate immunity in multiple sclerosis white matter lesions: expression of natural cytotoxicity triggering receptor 1 (NCR1).
BACKGROUND
Pathogenic or regulatory effects of natural killer (NK) cells are implicated in many autoimmune diseases, but evidence in multiple sclerosis (MS) and its murine models remains equivocal. In an effort to illuminate this, we have here analysed expression of the prototypic NK cell marker, NCR1 (natural cytotoxicity triggering receptor; NKp46; CD335), an activating receptor expressed by virtually all NK cells and therefore considered a pan-marker for NK cells. The only definitive ligand of NCR1 is influenza haemagglutinin, though there are believed to be others. In this study, we investigated whether there were differences in NCR1+ cells in the peripheral blood of MS patients and whether NCR1+ cells are present in white matter lesions.


RESULTS
We first investigated the expression of NCR1 on peripheral blood mononuclear cells and found no significant difference between healthy controls and MS patients. We then investigated mRNA levels in central nervous system (CNS) tissue from MS patients: NCR1 transcripts were increased more than 5 times in active disease lesions. However when we performed immunohistochemical staining of this tissue, few NCR1+ NK cells were identified. Rather, the major part of NCR1 expression was localised to astrocytes, and was considerably more pronounced in MS patients than controls. In order to further validate de novo expression of NCR1 in astrocytes, we used an in vitro staining of the human astrocytoma U251 cell line grown to model whether cell stress could be associated with expression of NCR1. We found up-regulation of NCR1 expression in U251 cells at both the mRNA and protein levels.


CONCLUSIONS
The data presented here show very limited expression of NCR1+ NK cells in MS lesions, the majority of NCR1 expression being accounted for by expression on astrocytes. This is compatible with a role of this cell-type and NCR1 ligand/receptor interactions in the innate immune response in the CNS in MS patients. This is the first report of NCR1 expression on astrocytes in MS tissue: it will now be important to unravel the nature of cellular interactions and signalling mediated through innate receptor expression on astrocytes.
Department of Medicine, Section of Infectious Diseases and Immunity, Commonwealth Building, Hammersmith Campus, Imperial College London, UK.
Pascal F
PF
Durrenberger
Anna
A
Ettorre
Fatemah
F
Kamel
Louise V
LV
Webb
Malcolm
M
Sim
Richard S
RS
Nicholas
Omar
O
Malik
Richard
R
Reynolds
Rosemary J
RJ
Boyton
Daniel M
DM
Altmann
D000328:Adult; D001253:Astrocytes / Q000378:metabolism; D001254:Astrocytoma / Q000473:pathology; D045744:Cell Line, Tumor; D002490:Central Nervous System / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005936:Glucans / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D007694:Killer Cells, Natural / Q000378:metabolism*; D008214:Lymphocytes / Q000166:cytology; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000473:pathology*; D055627:Natural Cytotoxicity Triggering Receptor 1 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
D005936:Glucans; D055627:Natural Cytotoxicity Triggering Receptor 1; D012333:RNA, Messenger; C083094:polyglucosan