Mass Cytometry of CSF Identifies an MS-Associated B-cell Population.

OBJECTIVE: To identify an MS-specific immune cell population by deep immune phenotyping and relate it to soluble signaling molecules in CSF. METHODS: We analyzed surface expression of 22 markers in paired blood/CSF samples from 39 patients using mass cytometry (cytometry by time of flight). We also measured the concentrations of 296 signaling molecules in CSF using proximity extension assay. Results were analyzed using highly automated unsupervised algorithmic informatics. RESULTS: Mass cytometry objectively identified a B-cell population characterized by the expression of CD49d, CD69, CD27, CXCR3, and human leukocyte antigen (HLA)-DR as clearly associated with MS. Concentrations of the B cell-related factors, notably FCRL2, were increased in MS CSF, especially in early stages of the disease. The B-cell trophic factor B cell activating factor (BAFF) was decreased in MS. Proteins involved in neural plasticity were also reduced in MS. CONCLUSION: When analyzed without a priori assumptions, both the soluble and the cellular compartments of the CSF in MS were characterized by markers related to B cells, and the strongest candidate for an MS-specific cell type has a B-cell phenotype.

The Emerging Jamboree of Transformative Therapies for Autoimmune Diseases.

Standard treatments for autoimmune and autoinflammatory disorders rely mainly on immunosuppression. These are predominantly symptomatic remedies that do not affect the root cause of the disease and are associated with multiple side effects. Immunotherapies are being developed during the last decades as more specific and safer alternatives to small molecules with broad immunosuppressive activity, but they still do not distinguish between disease-causing and protective cell targets and thus, they still have considerable risks of increasing susceptibility to infections and/or malignancy. Antigen-specific approaches inducing immune tolerance represent an emerging trend carrying the potential to be curative without inducing broad immunosuppression. These therapies are based on antigenic epitopes derived from the same proteins that are targeted by the autoreactive T and B cells, and which are administered to patients together with precise instructions to induce regulatory responses capable to restore homeostasis. They are not personalized medicines, and they do not need to be. They are precision therapies exquisitely targeting the disease-causing cells that drive pathology in defined patient populations. Immune tolerance approaches are truly transformative options for people suffering from autoimmune diseases.

Fingerprints of CD8+ T cells on human pre-plasma and memory B cells.

Differentiation of B cells is a stringently controlled multi-step process, which is still incompletely understood. Here we identify and characterize a rare population of human B cells, which surprisingly carry CD8AB on their surface. Existence of such cells was demonstrated both in tonsils and in human apheresis material. Gene expression profiling and real time PCR detected however no CD8A or CD8B message in these cells. Instead, we found that surface CD8 was hijacked from activated CD8+ T cells by a transfer process that required direct cell-to-cell contact. A focused transcriptome analysis at single cell level allowed the dissection of the CD8 positive B cell population. We found that the affected cells are characteristically of the CD27+CD200- phenotype, and consist of two discrete late-stage subpopulations that carry signatures of activated memory B like cells, and early plasmablasts. Thus, there is only a restricted time window in the differentiation process during which B cells can intimately interact with CD8+ T cells. The findings point to a novel link between the T and B arms of the adaptive immune system, and suggest that CD8+ T cells have the capability to directly shape the global antibody repertoire.

Identification of a SIRT1 mutation in a family with type 1 diabetes.

Type 1 diabetes is caused by autoimmune-mediated ß cell destruction leading to insulin deficiency. The histone deacetylase SIRT1 plays an essential role in modulating several age-related diseases. Here we describe a family carrying a mutation in the SIRT1 gene, in which all five affected members developed an autoimmune disorder: four developed type 1 diabetes, and one developed ulcerative colitis. Initially, a 26-year-old man was diagnosed with the typical features of type 1 diabetes, including lean body mass, autoantibodies, T cell reactivity to ß cell antigens, and a rapid dependence on insulin. Direct and exome sequencing identified the presence of a T-to-C exchange in exon 1 of SIRT1, corresponding to a leucine-to-proline mutation at residue 107. Expression of SIRT1-L107P in insulin-producing cells resulted in overproduction of nitric oxide, cytokines, and chemokines. These observations identify a role for SIRT1 in human autoimmunity and unveil a monogenic form of type 1 diabetes.

The aryl hydrocarbon receptor (AhR) ligand VAF347 selectively acts on monocytes and naïve CD4(+) Th cells to promote the development of IL-22-secreting Th cells.

The low molecular weight compound VAF347, and its pro-drug version VAG539, interact with the transcription factor aryl hydrocarbon receptor (AhR) on monocytes to mediate its anti-inflammatory activity in vitro and in vivo. AhR is a crucial factor for IL-22 production, which regulates skin and gut homeostasis. Here we investigated whether VAF347 might control the differentiation of naïve T cells into IL-22-secreting cells and/or regulate IL-22 production by memory T cells. Human monocytes exposed to VAF347 differentiated into dendritic cells capable of instructing a naïve CD4(+) T cell differentiation program that promoted IL-22 secretion and concomitantly inhibited IL-17 production. Whilst AhR ligation by VAF347 on naïve CD4(+) T cells favored the development of single IL-22-secreting cells (Th22), it suppressed the generation of T cells secreting either IL-22 and IFN-γ or IL-17 and IFN-γ. In contrast, memory T cells were refractory to AhR regulation since VAF347, AhR antagonist or AhR gene silencing did not modulate the production of any of these cytokines. Interfering with AhR functions using VAF347 may provide an efficient way to intervene with autoimmune disease since it would enhance the host protective function mediated by IL-22 while preventing the development of Th cells secreting pro-inflammatory cytokines.