Systemic immunosuppression depletes peripheral blood regulatory B cells in patients with immune thrombocytopenia.

Regulatory B (Breg) cells are potentially implicated in the pathogenesis of immune thrombocytopenia (ITP). We analysed a prospective cohort of newly diagnosed steroid naïve ITP patients enrolled in the multicentre FLIGHT trial and found that the numbers of Bregs in their peripheral blood were similar to healthy controls. In contrast, Breg numbers were significantly reduced in ITP patients treated with systemic immunosuppression (glucocorticoids or mycophenolate mofetil). We also demonstrate that glucocorticoid treatment impairs Breg interleukin-10 production via an indirect T-cell-mediated mechanism.

Glucocorticoid treatment in patients with newly diagnosed immune thrombocytopenia switches CD14++ CD16+ intermediate monocytes from a pro-inflammatory to an anti-inflammatory phenotype.

Immune thrombocytopenia (ITP) is thought to result from an aberrant adaptive autoimmune response, involving autoantibodies, B and T lymphocytes, directed at platelets and megakaryocytes. Previous reports have demonstrated skewed CD4+ T-helper subset distribution and enhanced production of pro-inflammatory cytokines such as interleukin 17A and interferon gamma. The role of monocytes (MCs) in ITP is less widely described, but innate immune cells have a role in shaping CD4+ T-cell phenotypes. Glucocorticoids (GCs) are commonly used for first-line ITP treatment and modulate a broad range of immune cells including T cells and MCs. Using multiparameter flow cytometry analysis, we demonstrate the expansion of intermediate MCs (CD14++ CD16+ ) in untreated patients with newly diagnosed ITP, with these cells displaying a pro-inflammatory phenotype, characterised by enhanced expression of CD64 and CD80. After 2 weeks of prednisolone treatment (1 mg/kg daily), the proportion of intermediate MCs reduced, with enhanced expression of the anti-inflammatory markers CD206 and CD163. Healthy control MCs were distinctly different than MCs from patients with ITP before and after GC treatment. Furthermore, the GC-induced phenotype was not observed in patients with chronic ITP receiving thrombopoietin receptor agonists. These data suggest a role of MCs in ITP pathogenesis and clinical response to GC therapy.

IL-10 and IL-17 expression by CD4+ T cells is altered in corticosteroid refractory immune thrombocytopenia (ITP).

BACKGROUND: Corticosteroids remain the first-line treatment for patients with immune thrombocytopenia (ITP). However, 20% to 30% of patients do not respond to treatment at tolerable doses. This variation in corticosteroid efficacy is replicated in other autoimmune diseases and may have an adaptive immune basis. OBJECTIVE: To test the hypothesis that CD4+ T-cell responses to corticosteroids are different in patients with clinically defined corticosteroid refractory ITP. METHODS: In this prospective cohort study, CD4+ T cells from patients with ITP were cultured in the presence or absence of dexamethasone (Dex). Intracellular cytokine expression was then quantified by flow cytometry and compared with patients' clinical response to corticosteroid treatment. A control cohort of patients with autoimmune uveitis was also studied to evaluate whether our findings were limited to ITP or are potentially generalizable across autoimmune diseases. RESULTS: The ratio of interleukin (IL)-10 to IL-17 expression following CD4+ T cell culture with Dex was able to discriminate between ITP patients with a clinically defined complete (n = 33), partial (n = 12) or nonresponse (n = 11) to corticosteroid treatment (P = .002). These findings were replicated in patients with autoimmune uveitis (complete response n = 14, nonresponse n = 22; P = .01). CONCLUSIONS: There is a relative abrogation of IL-10 and persistence of IL-17 expression in the CD4+ T cells of patients who clinically fail corticosteroid therapy. This observation has potential to inform both our mechanistic understanding of the action of corticosteroids in the treatment of ITP, and as a biomarker for steroid refractory disease, with potential application across a range of hematological and nonhematological conditions.

Modelling Macular Edema: The Effect of IL-6 and IL-6R Blockade on Human Blood-Retinal Barrier Integrity In Vitro.

PURPOSE: Macular edema (ME) is a leading cause of visual loss in a range of retinal diseases and despite the use of antivascular endothelial growth factor (anti-VEGF) agents, its successful treatment remains a major clinical challenge. Based on the indirect clinical evidence that interleukin-6 (IL-6) is a key additional candidate mediator of ME, we interrogated the effect of IL-6 on blood-retinal barrier (BRB) integrity in vitro. METHODS: Human retinal pigment epithelial cell (ARPE-19) and human retinal microvascular endothelial cell (HRMEC) monolayers were used to mimic the outer and inner BRB, respectively. Their paracellular permeability was assessed by measuring the passive permeation of 40 kDa fluorescein isothiocyanate (FITC)-dextran across confluent cells in the presence of IL-6. Transendothelial/epithelial electrical resistance (TEER) then was measured and the distribution of the tight junction protein ZO-1 was assessed by immunofluorescence using confocal microscopy. RESULTS: Treatment with IL-6 for 48 hours significantly increased the diffusion rate of FITC-dextran, decreased TEER, and disrupted the distribution of ZO-1 in ARPE-19 cells, which constitutively express the IL-6 transmembrane receptor, and this was reversed with IL-6R blockade. In contrast, IL-6 did not affect the paracellular permeability, TEER, or ZO-1 distribution in HRMECs. CONCLUSIONS: These in vitro data support the hypothesis that IL-6 reversibly disrupts the integrity of ARPE-19 cells, but it does not affect HRMECs. TRANSLATIONAL RELEVANCE: IL-6 is a candidate therapeutic target in the treatment of outer BRB driven ME.

Re-programming immunosurveillance in persistent non-infectious ocular inflammation.

Ocular function depends on a high level of anatomical integrity. This is threatened by inflammation, which alters the local tissue over short and long time-scales. Uveitis due to autoimmune disease, especially when it involves the retina, leads to persistent changes in how the eye interacts with the immune system. The normal pattern of immune surveillance, which for immune privileged tissues is limited, is re-programmed. Many cell types, that are not usually present in the eye, become detectable. There are changes in the tissue homeostasis and integrity. In both human disease and mouse models, in the most extreme cases, immunopathological findings consistent with development of ectopic lymphoid-like structures and disrupted angiogenesis accompany severely impaired eye function. Understanding how the ocular environment is shaped by persistent inflammation is crucial to developing novel approaches to treatment.

The Bromodomain and Extra-Terminal Protein Inhibitor OTX015 Suppresses T Helper Cell Proliferation and Differentiation.

BACKGROUND: Dynamic epigenetic alterations accompanying CD4+ T helper cell differentiation have been implicated in multiple autoimmune diseases. The bromodomain and extra-terminal (BET) proteins are epigenetic regulators that recognize and bind to acetylated histones in chromatin and are targets for pharmacological inhibition. In this study we tested a new BET inhibitor under clinical development, OTX015, to interrogate its effects on key CD4+ T cell subsets associated with autoimmunity. METHODS: Naïve and memory murine and human CD4+ T cells were isolated and differentiated into populations characterized by the expression of interferon (IFN)-γ and interleukin (IL)-17. Cultured cells were then exposed to varying concentrations of OTX015 in vitro, and its impact on cytokine expression was quantified by flow cytometry. In parallel, the expression of the transcription factors TBX21 and RORC was quantified by PCR. A previously studied BET inhibitor JQ1 was used as a pharmacological control. RESULTS: OTX015 suppressed both murine and human CD4+ T cell proliferation. Its impact on cytokine expression varied in murine and human naïve and memory subsets. OTX015 was similarly effective as JQ1 in the suppression of cytokines and T helper cell proliferation. Higher concentrations of OTX015 also had a greater impact on the viability of murine versus human cells. IL-17 and IFN-γ expression was not altered in murine memory CD4+ T cells, whereas in human memory CD4+ T cells, OTX015 inhibited IL-17, but not IFN-γ. Across all human T cell subsets OTX015 suppressed IL-17 more effectively than IFN-γ. CONCLUSION: Our studies demonstrate that OTX015 has anti-inflammatory effects by suppressing murine and human CD4+ T cell proliferation and subset-dependent proinflammatory cytokine expression, including the selective suppression of IL-17 in human memory CD4+ T cells.

Development and validation of a novel bioassay to determine glucocorticoid sensitivity.

BACKGROUND: Glucocorticoids (GCs) remain the first line treatment for almost all non-infectious inflammatory diseases, ranging from acute asthma to rheumatoid arthritis. However, across all conditions, patients have a variable response to GCs with approximately 30% being non-responders. This group of GC resistant patients is typically exposed to high-dose GCs and their side-effects before more appropriate immunotherapy is instituted. Hence, there is a pressing clinical need for a predictive biomarker of GC responsiveness. The availability of such a tool would also enable patient stratification for the conduct of smart clinical trials in GC resistance. Lymphocyte GC sensitivity has been shown to be closely associated with clinical GC sensitivity in a number of inflammatory diseases. However, the method for determining in vitro GC response is not standardized and requires the use of specialist equipment, including a radioisotope to quantify cellular proliferation, making it challenging to translate into clinical practice. RESULTS: Here we describe the optimization and validation of a novel non-radioactive in vitro bioassay based on measuring cellular proliferation by incorporation of bromodeoxyuridine (BrdU), termed the BrdU incorporation in lymphocyte steroid sensitivity assay (BLISS). In comparison to the current gold standard lymphocyte GC sensitivity assay in 101 healthy control samples, BLISS has an area under receiver operating characteristic of 0.82 and a sensitivity of 83% for correctly identifying GC resistant subjects. CONCLUSIONS: The performance of the novel BLISS bioassay makes it a strong candidate biomarker for clinical application. It now requires validation in a prospective patient cohort.

A novel pathogenic RBP-3 peptide reveals epitope spreading in persistent experimental autoimmune uveoretinitis.

Experimental autoimmune uveoretinitis (EAU) in the C57BL/6J mouse is a model of non-infectious posterior segment intraocular inflammation that parallels clinical features of the human disease. The purpose of this study was to analyse the immune response to the four murine subunits of retinol binding protein-3 (RBP-3) to identify pathogenic epitopes to investigate the presence of intramolecular epitope spreading during the persistent inflammation phase observed in this model of EAU. Recombinant murine subunits of the RBP-3 protein were purified and used to immunize C57BL/6J mice to induce EAU. An overlapping peptide library was used to screen RBP-3 subunit 3 for immunogenicity and pathogenicity. Disease phenotype and characterization of pathogenic subunits and peptides was undertaken by topical endoscopic fundal imaging, immunohistochemistry, proliferation assays and flow cytometry. RBP-3 subunits 1, 2 and 3 induced EAU in the C57BL/6J mice, with subunit 3 eliciting the most destructive clinical disease. Within subunit 3 we identified a novel uveitogenic epitope, 629-643. The disease induced by this peptide was comparable to that produced by the uveitogenic 1-20 peptide. Following immunization, peptide-specific responses by CD4(+) and CD8(+) T-cell subsets were detected, and cells from both populations were present in the retinal inflammatory infiltrate. Intramolecular epitope spreading between 629-643 and 1-20 was detected in mice with clinical signs of disease. The 629-643 RBP-3 peptide is a major uveitogenic peptide for the induction of EAU in C57BL/6J mice and the persistent clinical disease induced with one peptide leads to epitope spreading.