Role of CD8+ CD25+ Foxp3+ regulatory T cells in multiple sclerosis.
OBJECTIVE
The objective of this study was to investigate the role of CD8+ CD25+ FoxP3+ cells during the course of multiple sclerosis (MS).


METHODS
Peripheral blood and cerebrospinal fluid (CSF) CD8+ T-cell clones (TCCs) recognizing autoreactive CD4+ T cells were isolated from 20 MS patients during exacerbations, 15 patients in remission, 15 healthy subjects, and 10 patients with other inflammatory neurological diseases. Characteristics of noncytotoxic CD8+ CD25+ regulatory T cells were studied. Cell phenotype was evaluated using flow cytometry. Cytokine production and phospho-signal transducer and activator of transcription 3 (STAT3) concentration were determined using enzyme-linked immunosorbent assay. To assess 2,3-dioxygenase (IDO) activity on dendritic cells (DCs), kynurenine concentration was measured by high-performance liquid chromatography.


RESULTS
Inhibition of CD4+ self-reactive T-cell proliferation, and of interferon-gamma and interleukin (IL)-17 secretion, was observed after adding CD8+ CD25+ FoxP3+ cells to cultures. Suppression was abrogated by silencing FoxP3 using small interfering RNA. Cells were CD122+, CTLA-4+, GITR+, CCR7+, and CD62L+, producing IL-10 and transforming growth factor-beta. CD8+ CD25+ FoxP3+ cells downregulated costimulatory molecule expression on dendritic cells through a STAT3-mediated pathway, resulting in less efficient antigen presentation, and induced IDO expression on DCs through STAT3 and cytotoxic T-lymphocyte antigen 4-dependent mechanisms. CD8+ regulatory TCC cloning frequency studied in blood and CSF was suppressed to a greater degree during exacerbations than during remission or in controls. Likewise, in CSF of MS patients during acute exacerbations, lower levels of CD8+ CD25+ FoxP3+ T cells were detected using flow cytometry.


CONCLUSIONS
CD8+ CD25+ FoxP3+ cells are novel regulatory cells exerting significant influence over self-reactive CD4+ T-cell regulation during the course of MS. Induction of these cells may provide new therapeutic alternatives for MS by eliminating or inhibiting self-reactive T cells.
Correale
Jorge
J
Department of Neurology, Institute for Neurological Research Dr Raúl Carrea, FLENI, Buenos Aires, Argentina. jcorreale@fleni.org.ar
Villa
Andrés
A
D000328:Adult; D015704:CD4 Antigens / Q000494:pharmacology; D016827:CD8 Antigens / Q000378:metabolism*; D049109:Cell Proliferation; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003713:Dendritic Cells / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D016753:Interleukin-10 / Q000378:metabolism; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism*; D016015:Logistic Models; D008297:Male; D009103:Multiple Sclerosis / Q000473:pathology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000502:physiology*
D015704:CD4 Antigens; D016827:CD8 Antigens; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D053645:Interleukin-2 Receptor alpha Subunit; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D016753:Interleukin-10; D007371:Interferon-gamma