Mammalian target of rapamycin complex 2 regulates invariant NKT cell development and function independent of promyelocytic leukemia zinc-finger.

The mammalian target of rapamycin (mTOR) senses and incorporates different environmental cues via the two signaling complexes mTOR complex 1 (mTORC1) and mTORC2. As a result, mTOR controls cell growth and survival, and also shapes different effector functions of the cells including immune cells such as T cells. We demonstrate in this article that invariant NKT (iNKT) cell development is controlled by mTORC2 in a cell-intrinsic manner. In mice deficient in mTORC2 signaling because of the conditional deletion of the Rictor gene, iNKT cell numbers were reduced in the thymus and periphery. This is caused by decreased proliferation of stage 1 iNKT cells and poor development through subsequent stages. Functionally, iNKT cells devoid of mTORC2 signaling showed reduced number of IL-4-expressing cells, which correlated with a decrease in the transcription factor GATA-3-expressing cells. However, promyelocytic leukemia zinc-finger (PLZF), a critical transcription factor for iNKT cell development, is expressed at a similar level in mTORC2-deficient iNKT cells compared with that in the wild type iNKT cells. Furthermore, cellular localization of PLZF was not altered in the absence of mTOR2 signaling. Thus, our study reveals the PLZF-independent mechanisms of the development and function of iNKT cells regulated by mTORC2.

What happens to endoscopic/arthroscopic tenotomies with iliopsoas impingement in the medium term? Review of a prospective cohort of 64 patients with a minimum follow-up of 5 years.

INTRODUCTION: The occurrence of iliopsoas impingement (IPI) after total hip arthroplasty (THA) is a proven risk factor for negative outcomes. Endoscopic or arthroscopic tenotomies of the iliopsoas offer a surgical solution with short-term results that have already been validated in prospective multicenter series. We carried out a review of the patients at more than 5 years of follow-up in order to assess the stability of the results over time. HYPOTHESIS: Our main hypothesis was that endoscopic/arthroscopic tenotomies allow stable medium-term resolution of the painful symptoms of IPI. Our secondary hypothesis was that medium-term survival was satisfactory. MATERIAL AND METHOD: This study is a continuation of a multicenter prospective series. Patients were contacted through multiple channels in order to: obtain an Oxford score, assess for satisfaction, psoas irritation, and daily pain on a visual analogue scale (VAS). RESULTS: Of 64 patients in the original study, 57 were contacted. The Oxford score at the last follow-up was 40.7±7.7 [12-48]. There was a significant difference between the Oxford scores preoperatively, at 8 months and at the last follow-up. The mean satisfaction out of 10 was 8.0±2.1 [1-10]. We found 84% satisfaction at 5 years against 83% at 8 months. The VAS was 2.1±2.3 [0-10]. A straight leg psoas sign was present in 19.6% (10/51) of patients at 5 years, compared to 15.6% (8/51) at 8 months. The sign disappeared in four cases, while it reappeared during the interval in six cases. Survival was 91.2% (95% CI: 80.2-96.3) at 5 years. CONCLUSION: Endoscopic/arthroscopic iliopsoas tenotomies represent a permanent medium-term solution to treat IPI after THA. The existence of a force differential or an acetabular overhang does not seem, within a certain limit, to impact the results in the medium term. LEVEL OF EVIDENCE: IV; prospective series without control group.

Abrogation of ICOS/ICOS ligand costimulation in NOD mice results in autoimmune deviation toward the neuromuscular system.

NOD mice spontaneously develop insulin-dependent diabetes around 10-40 wk of age. Numerous immune gene variants contribute to the autoimmune process. However, genes that direct the autoimmune response toward ß cells remain ill defined. In this study, we provide evidence that the Icos and Icosl genes contribute to the diabetes process. Protection from diabetes in ICOS(-/-) and ICOSL(-/-) NOD mice was unexpectedly associated with the development of an autoimmune disorder of the neuro-muscular system, characterized by myositis, sensory ganglionitis and, to a reduced extent, inflammatory infiltrates in the CNS. This syndrome was reproduced upon adoptive transfer of CD4(+) and CD8(+) T cells from diseased donors to naïve NOD.scid recipients. Our data further show that protection from diabetes results from defective activation of autoimmune diabetogenic effector T cells in ICOS(-/-) NOD mice, whereas acceleration of diabetes in BDC2.5 ICOS(-/-) NOD mice is induced by a dominant defect in Treg. Taken together, our findings indicate that costimulation signals play a key role in regulating immune tolerance in peripheral tissues and that the ICOS/ICOSL costimulatory pathway influences the balance between Treg and diabetogenic effector T cells.

The chaperonin CCT8 controls proteostasis essential for T cell maturation, selection, and function.

T cells rely for their development and function on the correct folding and turnover of proteins generated in response to a broad range of molecular cues. In the absence of the eukaryotic type II chaperonin complex, CCT, T cell activation induced changes in the proteome are compromised including the formation of nuclear actin filaments and the formation of a normal cell stress response. Consequently, thymocyte maturation and selection, and T cell homeostatic maintenance and receptor-mediated activation are severely impaired. In the absence of CCT-controlled protein folding, Th2 polarization diverges from normal differentiation with paradoxical continued IFN-γ expression. As a result, CCT-deficient T cells fail to generate an efficient immune protection against helminths as they are unable to sustain a coordinated recruitment of the innate and adaptive immune systems. These findings thus demonstrate that normal T cell biology is critically dependent on CCT-controlled proteostasis and that its absence is incompatible with protective immunity.

FOXN1 forms higher-order nuclear condensates displaced by mutations causing immunodeficiency.

The transcription factor FOXN1 is a master regulator of thymic epithelial cell (TEC) development and function. Here, we demonstrate that FOXN1 expression is differentially regulated during organogenesis and participates in multimolecular nuclear condensates essential for the factor's transcriptional activity. FOXN1's C-terminal sequence regulates the diffusion velocity within these aggregates and modulates the binding to proximal gene regulatory regions. These dynamics are altered in a patient with a mutant FOXN1 that is modified in its C-terminal sequence. This mutant is transcriptionally inactive and acts as a dominant negative factor displacing wild-type FOXN1 from condensates and causing athymia and severe lymphopenia in heterozygotes. Expression of the mutated mouse ortholog selectively impairs mouse TEC differentiation, revealing a gene dose dependency for individual TEC subtypes. We have therefore identified the cause for a primary immunodeficiency disease and determined the mechanism by which this FOXN1 gain-of-function mutant mediates its dominant negative effect.

Inhibition of type 1 diabetes by upregulation of the circadian rhythm-related aryl hydrocarbon receptor nuclear translocator-like 2.

The genetic locus Idd6 is involved in type 1 diabetes development in the non-obese diabetic (NOD) mouse through its effect on the immune system and in particular, on T cell activities. Analysis of congenic strains for Idd6 has established the Aryl hydrocarbon receptor nuclear translocator-like 2 (Arntl2) as a likely candidate gene. In this study we investigate the role of Arntl2 in the autoimmune disease and T cell activation. An Arntl2 expressing plasmid was transfected into CD4(+) T cells by nucleofection. Expression levels of cytokines and CD4(+) T cell activation markers, cell death, apoptosis, and cell proliferation rates were characterized in ex vivo experiments whilst in vivo the transfected cells were transferred into NOD.SCID mice to monitor diabetes development. The results demonstrate that Arntl2 overexpression leads to inhibition of CD4(+) T cell proliferation and decreases in their diabetogenic activity without influence on the expression levels of cytokines, CD4(+) T cell activation markers, cell death, and apoptosis. Our findings suggest that Arntl2 at the Idd6 locus may act via the inhibition of CD4(+) T cell proliferation and the reduction in the diabetogenic activity of CD4(+) T cells to protect against autoimmune type 1 diabetes in the NOD mice.

The Spontaneous Autoimmune Neuromyopathy in ICOSL-/- NOD Mice Is CD4+ T-Cell and Interferon-γ Dependent.

Abrogation of ICOS/ICOS ligand (ICOSL) costimulation prevents the onset of diabetes in the non-obese diabetic (NOD) mouse but, remarkably, yields to the development of a spontaneous autoimmune neuromyopathy. At the pathological level, ICOSL-/- NOD mice show stronger protection from insulitis than their ICOS-/- counterparts. Also, the ICOSL-/- NOD model carries a limited C57BL/6 region containing the Icosl nul mutation, but, in contrast to ICOS-/- NOD mice, no gene variant previously reported as associated to NOD diabetes. Therefore, we aimed at providing a detailed characterization of the ICOSL-/- NOD model. The phenotype observed in ICOSL-/- NOD mice is globally similar to that observed in ICOS-/- and ICOS-/-ICOSL-/- double-knockout NOD mice, manifested by a progressive locomotor disability first affecting the front paws as observed by catwalk analysis and a decrease in grip test performance. The pathology remains limited to peripheral nerve and striated muscle. The muscle disease is characterized by myofiber necrosis/regeneration and an inflammatory infiltrate composed of CD4+ T-cells, CD8+ T-cells, and myeloid cells, resembling human myositis. Autoimmune neuromyopathy can be transferred to NOD.scid recipients by CD4+ but not by CD8+ T-cells isolated from 40-week-old female ICOSL-/- NOD mice. The predominant role of CD4+ T-cells is further demonstrated by the observation that neuromyopathy does not develop in CIITA-/-ICOSL-/- NOD in contrast to ß2microglobulin-/-ICOSL-/- NOD mice. Also, the cytokine profile of CD4+ T-cells infiltrating muscle and nerve of ICOSL-/- NOD mice is biased toward a Th1 pattern. Finally, adoptive transfer experiments show that diabetes development requires expression of ICOSL, in contrast to neuromyopathy. Altogether, the deviation of autoimmunity from the pancreas to skeletal muscles in the absence of ICOS/ICOSL signaling in NOD mice is strictly dependent on CD4+ T-cells, leads to myofiber necrosis and regeneration. It provides the first mouse model of spontaneous autoimmune myopathy akin to human myositis.