Notch-regulated miR-223 targets the aryl hydrocarbon receptor pathway and increases cytokine production in macrophages from rheumatoid arthritis patients.

Evidence links aryl hydrocarbon receptor (AHR) activation to rheumatoid arthritis (RA) pathogenesis, although results are inconsistent. AHR agonists inhibit pro-inflammatory cytokine expression in macrophages, pivotal cells in RA aetiopathogenesis, which hints at specific circuits that regulate the AHR pathway in RA macrophages. We compared microRNA (miR) expression in CD14(+) cells from patients with active RA or with osteoarthritis (OA). Seven miR were downregulated and one (miR-223) upregulated in RA compared to OA cells. miR-223 upregulation correlated with reduced Notch3 and Notch effector expression in RA patients. Overexpression of the Notch-induced repressor HEY-1 and co-culture of healthy donor monocytes with Notch ligand-expressing cells showed direct Notch-mediated downregulation of miR-223. Bioinformatics predicted the AHR regulator ARNT (AHR nuclear translocator) as a miR-223 target. Pre-miR-223 overexpression silenced ARNT 3'UTR-driven reporter expression, reduced ARNT (but not AHR) protein levels and prevented AHR/ARNT-mediated inhibition of pro-inflammatory cytokine expression. miR-223 counteracted AHR/ARNT-induced Notch3 upregulation in monocytes. Levels of ARNT and of CYP1B1, an AHR/ARNT signalling effector, were reduced in RA compared to OA synovial tissue, which correlated with miR-223 levels. Our results associate Notch signalling to miR-223 downregulation in RA macrophages, and identify miR-223 as a negative regulator of the AHR/ARNT pathway through ARNT targeting.

A leaky mutation in CD3D differentially affects αß and γδ T cells and leads to a Tαß-Tγδ+B+NK+ human SCID.

T cells recognize antigens via their cell surface TCR and are classified as either αß or γδ depending on the variable chains in their TCR, α and ß or γ and δ, respectively. Both αß and γδ TCRs also contain several invariant chains, including CD3δ, which support surface TCR expression and transduce the TCR signal. Mutations in variable chains would be expected to affect a single T cell lineage, while mutations in the invariant chains would affect all T cells. Consistent with this, all CD3δ-deficient patients described to date showed a complete block in T cell development. However, CD3δ-KO mice have an αß T cell-specific defect. Here, we report 2 unrelated cases of SCID with a selective block in αß but not in γδ T cell development, associated with a new splicing mutation in the CD3D gene. The patients' T cells showed reduced CD3D transcripts, CD3δ proteins, surface TCR, and early TCR signaling. Their lymph nodes showed severe T cell depletion, recent thymus emigrants in peripheral blood were strongly decreased, and the scant αß T cells were oligoclonal. T cell-dependent B cell functions were also impaired, despite the presence of normal B cell numbers. Strikingly, despite the specific loss of αß T cells, surface TCR expression was more reduced in γδ than in αß T cells. Analysis of individuals with this CD3D mutation thus demonstrates the contrasting CD3δ requirements for αß versus γδ T cell development and TCR expression in humans and highlights the diagnostic and clinical relevance of studying both TCR isotypes when a T cell defect is suspected.

Frequency of BCL2 and BCL6 translocations in follicular lymphoma: relation with histological and clinical features.

Follicular lymphomas (FLs) usually carry BCL2 translocations although BCL6 translocations are also present. We explored relationships between translocations status and clinical or histological parameters at diagnosis in 182 patients stratified in four groups: BCL2-/BCL6-, BCL2+/BCL6-, BCL2-/BCL6+ and BCL2+/BCL6+. BCL2-/BCL6- and BCL2+/BCL6-. Double negative cases were ascribed to lower histological grades. In contrast, BCL2-/BCL6+ cases corresponded to higher grades. However, a majority of BCL2+/BCL6+ tumours were classified as lower grades. These results were reinforced by the finding that double positive patients had lower LDH levels and PS than those with solitary BCL6 rearrangements. Bone marrow involvement was more frequent in BCL2+/BCL6+ compared with BCL2-/BCL6+ tumours. Our data confirm the presence of a relationship between histological grade and translocation status, suggesting that FLs carrying BCL6 translocations probably constitute a special biological subtype. Clinical and histological differences between BCL2-/BCL6+ and BCL2+/BCL6+ tumours could reflect an interplay between both translocations.

IL-10 production in B cells is confined to CD154+ cells in patients with systemic lupus erythematosus.

The immunological hallmark of SLE is B cell hyperactivity. CD154 (CD40-L) is normally expressed in activated T cells, and plays an important role in T-B interactions. Its expression is increased in SLE T cells. Additionally, its expression on B cells leads to the development of SLE-like disease in a transgenic model. IL-10 is a key cytokine in the disturbed SLE immune system. The aim of this work was to explore the relation between IL-10 and CD154 expression in SLE B cells. We studied 11 SLE patients and 10 healthy volunteers. Mononuclear cells were isolated from peripheral blood and cultured in the presence or absence of Cowan I Strain Staphylococcus (CSS). Surface CD154 and intracytoplasmic IL-10 expression were quantified with flow cytometry. In basal conditions, CD154 expression was not different in patients and controls. B cell stimulation did not cause a significant increase in CD154 expression in control B cells. However, its expression increased 2 times in B cells obtained from SLE patients. IL-10 expression was confined to CD154(+) cells. Our results show that IL-10 production is intimately linked to CD154 expression in B cells, and that the IL-10(+)CD154(+) B cell subset increases abnormally when SLE-derived cells are stimulated with CSS.