The CCR6/CCL20 axis expands RORγt+ Tregs to protect from glomerulonephritis.

Previous studies have identified a unique Treg population, which expresses the Th17 characteristic transcription factor RORγt. These RORγt+ Tregs possess enhanced immunosuppressive capacity, which endows them with great therapeutic potential. However, as a caveat, they are also capable of secreting pro-inflammatory IL-17A. Since the sum function of RORγt+ Tregs in glomerulonephritis (GN) remains unknown, we studied the effects of their absence. Purified CD4+ T cell populations, containing or lacking RORγt+ Tregs, were transferred into immunocompromised RAG1 knockout mice and the nephrotoxic nephritis model of GN was induced. Absence of RORγt+ Tregs significantly aggravated kidney injury, demonstrating overall kidney-protective properties. Analyses of immune responses showed that RORγt+ Tregs were broadly immunosuppressive with no preference for a particular type of T cell response. Further characterization revealed a distinct functional and transcriptional profile, including enhanced production of IL-10. Expression of the chemokine receptor CCR6 marked a particularly potent subset, whose absence significantly worsened GN. As an underlying mechanism, we found that chemokine CCL20 acting through receptor CCR6 signaling mediated expansion and activation of RORγt+ Tregs. Finally, we also detected an increase of CCR6+ Tregs in kidney biopsies, as well as enhanced secretion of chemokine CCL20 in 21 patients with anti-neutrophil cytoplasmic antibody associated GN compared to that of 31 healthy living donors, indicating clinical relevance. Thus, our data characterize RORγt+ Tregs as anti-inflammatory mediators of GN and identify them as promising target for Treg directed therapies.

Secondary immune-mediated thrombotic thrombocytopenic purpura in idiopathic inflammatory myopathy: a case-based review.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal acquired thrombotic microangiopathy syndrome that frequently develops in the context of infectious diseases or systemic autoimmune conditions including connective tissue diseases. We report the case of a 42-year-old female suffering from severe iTTP associated with anti-Jo-1 positive antisynthetase syndrome, which was successfully treated with combination therapy of intravenous immune globulin, rituximab and plasma exchange. Based on a systematic review of the literature, two additional cases of idiopathic inflammatory myopathy-associated iTTP (secondary iTTP) were identified. In conclusion, iTTP may be a rare complication of IIM that clinicians should consider in cases of marked thrombocytopenia. Further work-up of this finding should include a peripheral blood smear (schistocyte count) and ADAMTS13 activity. The concomitant manifestation of these autoimmune conditions may require intensive immunosuppressive therapy.

[Renal manifestations in connective tissue diseases]. / Nierenbeteiligung bei Kollagenosen.

Connective tissue diseases (CTD) comprise a group of inflammatory systemic diseases that can affect various organs. Kidney involvement is frequently associated with significant irreversible damage and often before patients become symptomatic. Screening tests of blood and urine as well as clinical vigilance are therefore essential for all CTDs with possible renal involvement. A kidney biopsy is the gold standard for the diagnosis, prognosis and treatment decisions. A common and severe organ involvement in systemic lupus erythematosus (SLE) is glomerulonephritis (GN), also collectively referred to as lupus nephritis (LN). If left untreated LN often leads to end-stage renal failure. The treatment depends on the clinical parameters and histopathology of the renal involvement. Mycophenolate mofetil and cyclophosphamide are potent but nonspecific immunosuppressants which have been available for many years. Recently, new substances specific for LN have also been approved for the first time. Kidney involvement in Sjogren's syndrome has been far less studied. In studies the frequency of renal involvement is still unclear and ranges from 5% to 33%. Tubulointerstitial nephritis (IN) is the typical form of renal involvement which clearly differs from GN in its clinical presentation. Recommendations for treatment are based exclusively on retrospective studies. A renal crisis in systemic scleroderma (SSc) is a rare but feared complication with a high mortality. An antiphospholipid syndrome (APS) nephropathy (APSN) can occur during CTD. These entities are vasculopathies and often thrombotic microangiopathies, which clearly differ from GN and IN in terms of pathophysiology, clinical features and treatment. This article provides an overview of the diversity of the most important renal manifestations of CTDs.

[Sarcoidosis as prime example of a granulomatous disease]. / Sarkoidose als Paradebeispiel einer granulomatösen Erkrankung.

Sarcoidosis is the most frequent immunologically related granulomatous disease and can serve as a model for understanding diseases within this category. The evidence on the diagnostics and treatment is so far limited. It is therefore all the more important that two new and significant guidelines on diagnosis and treatment of sarcoidosis were published during the last 2 years. Additionally, there were more new publications, which were considered for this review article. In this context, this review article provides a current update and overview of sarcoidosis. Pathophysiologically, there is an increasing understanding of the complex processes and interactions involved in the inflammatory processes and granuloma formation. The probability of a diagnosis of sarcoidosis is determined by compatible histology, the exclusion of differential diagnoses and if possible evidence of a multiorgan manifestation. The clinical course is variable and ranges from an asymptomatic manifestation to severe life-threatening organ failure. The most frequently affected organ are the lungs. Pulmonary fibrosis is the most severe form and is also decisive for mortality. An increasing focus is on the extrapulmonary organ manifestations, in particular, cardiac, hepatosplenic, gastrointestinal, renal, ocular and neurological involvement. Treatment, which consists primarily of immunosuppression, should be initiated in cases of organ-threatening or quality of life-impairing activity of the disease. Additional organ-specific management must also be evaluated. In cases of organ failure transplantation should be considered. Due to the limited evidence especially for the treatment of multiorgan sarcoidosis, when possible, patients with this disease should be included in clinical trials.

Antigen Cross-Presentation by Murine Proximal Tubular Epithelial Cells Induces Cytotoxic and Inflammatory CD8+ T Cells.

Immune-mediated glomerular diseases are characterized by infiltration of T cells, which accumulate in the periglomerular space and tubulointerstitium in close contact to proximal and distal tubuli. Recent studies described proximal tubular epithelial cells (PTECs) as renal non-professional antigen-presenting cells that stimulate CD4+ T-cell activation. Whether PTECs have the potential to induce activation of CD8+ T cells is less clear. In this study, we aimed to investigate the capacity of PTECs for antigen cross-presentation thereby modulating CD8+ T-cell responses. We showed that PTECs expressed proteins associated with cross-presentation, internalized soluble antigen via mannose receptor-mediated endocytosis, and generated antigenic peptides by proteasomal degradation. PTECs induced an antigen-dependent CD8+ T-cell activation in the presence of soluble antigen in vitro. PTEC-activated CD8+ T cells expressed granzyme B, and exerted a cytotoxic function by killing target cells. In murine lupus nephritis, CD8+ T cells localized in close contact to proximal tubuli. We determined enhanced apoptosis in tubular cells and particularly PTECs up-regulated expression of cleaved caspase-3. Interestingly, induction of apoptosis in the inflamed kidney was reduced in the absence of CD8+ T cells. Thus, PTECs have the capacity for antigen cross-presentation thereby inducing cytotoxic CD8+ T cells in vitro, which may contribute to the pathology of immune-mediated glomerulonephritis.

The Amphiregulin/EGFR axis protects from lupus nephritis via downregulation of pathogenic CD4+ T helper cell responses.

Systemic lupus erythematosus (SLE) is a common autoimmune disorder with a complex and poorly understood immuno-pathogenesis. Lupus nephritis (LN) is a frequent and difficult to treat complication, which causes high morbidity and mortality. The multifunctional cytokine amphiregulin (AREG) has been implicated in SLE pathogenesis, but its function in LN currently remains unknown. We thus studied the model of pristane-induced LN and found increasing renal and systemic AREG expression during the course of disease. Importantly, renal injury was significantly aggravated in the absence of AREG, revealing a net anti-inflammatory role. Analyses of immune responses showed dual effects. On the one hand, AREG enhanced activation of pro-inflammatory myeloid cells, which however did not play a major role for the course of LN. More importantly, on the other hand, AREG strongly suppressed pathogenic cytokine production by T helper effector cells. This effect was more general in nature and could be reproduced in response to antigen immunization. Since AREG has been postulated to downregulate T cell responses via enhancing Treg suppressive capacity, we followed up on this aspect. Interestingly, however, in vitro studies revealed potential direct and Treg independent effects of AREG on T helper effector cells. In favor of this notion, we found significantly enhanced T cell responses and consecutive aggravation of LN, only if epidermal growth factor receptor (EGFR) signaling was abrogated in total T cells, but not if the EGFR was absent on Tregs alone. Finally, we also found enhanced AREG expression in plasma and renal biopsies of patients with LN, supporting the relevance of our findings for human disease. In summary, our data identify AREG as an anti-inflammatory mediator of LN via broad downregulation of pathogenic T cell immunity. These findings further highlight the AREG/EGFR axis as a potential therapeutic target.

Amphiregulin Aggravates Glomerulonephritis via Recruitment and Activation of Myeloid Cells.

BACKGROUND: Recent studies have identified the EGF receptor (EGFR) ligand amphiregulin (AREG) as an important mediator of inflammatory diseases. Both pro- and anti-inflammatory functions have been described, but the role of AREG in GN remains unknown. METHODS: The nephrotoxic nephritis model of GN was studied in AREG-/- mice after bone marrow transplantation, and in mice with myeloid cell-specific EGFR deficiency. Therapeutic utility of AREG neutralization was assessed. Furthermore, AREG's effects on renal cells and monocytes/macrophages (M/M) were analyzed. Finally, we evaluated AREG expression in human renal biopsies. RESULTS: Renal AREG mRNA was strongly upregulated in murine GN. Renal resident cells were the most functionally relevant source of AREG. Importantly, the observation that knockout mice showed significant amelioration of disease indicates that AREG is pathogenic in GN. AREG enhanced myeloid cell responses via inducing chemokine and colony stimulating factor 2 (CSF2) expression in kidney resident cells. Furthermore, AREG directly skewed M/M to a proinflammatory M1 phenotype and protected them from apoptosis. Consequently, anti-AREG antibody treatment dose-dependently ameliorated GN. Notably, selective abrogation of EGFR signaling in myeloid cells was sufficient to protect against nephritis. Finally, strong upregulation of AREG expression was also detected in kidneys of patients with two forms of crescentic GN. CONCLUSIONS: AREG is a proinflammatory mediator of GN via (1) enhancing renal pathogenic myeloid cell infiltration and (2) direct effects on M/M polarization, proliferation, and cytokine secretion. The AREG/EGFR axis is a potential therapeutic target for acute GN.

A Novel Role for IL-6 Receptor Classic Signaling: Induction of RORγt+Foxp3+ Tregs with Enhanced Suppressive Capacity.

BACKGROUND: New therapies blocking the IL-6 receptor (IL-6R) have recently become available and are successfully being used to treat inflammatory diseases like arthritis. Whether IL-6 blockers may help patients with kidney inflammation currently remains unknown. METHODS: To learn more about the complex role of CD4+ T cell-intrinsic IL-6R signaling, we induced nephrotoxic nephritis, a mouse model for crescentic GN, in mice lacking T cell-specific IL-6Ra. We used adoptive transfer experiments and studies in reporter mice to analyze immune responses and Treg subpopulations. RESULTS: Lack of IL-6Ra signaling in mouse CD4+ T cells impaired the generation of proinflammatory Th17 cells, but surprisingly did not ameliorate the course of GN. In contrast, renal damage was significantly reduced by restricting IL-6Ra deficiency to T effector cells and excluding Tregs. Detailed studies of Tregs revealed unaltered IL-10 production despite IL-6Ra deficiency. However, in vivo and in vitro, IL-6Ra classic signaling induced RORγt+Foxp3+ double-positive Tregs (biTregs), which carry the trafficking receptor CCR6 and have potent immunoregulatory properties. Indeed, lack of IL-6Ra significantly reduced Treg in vitro suppressive capacity. Finally, adoptive transfer of T cells containing IL-6Ra-/- Tregs resulted in severe aggravation of GN in mice. CONCLUSIONS: Our data refine the old paradigm, that IL-6 enhances Th17 responses and suppresses Tregs. We here provide evidence that T cell-intrinsic IL-6Ra classic signaling indeed induces the generation of Th17 cells but at the same time highly immunosuppressive RORγt+ biTregs. These results advocate caution and indicate that IL-6-directed therapies for GN need to be cell-type specific.

T-Bet Enhances Regulatory T Cell Fitness and Directs Control of Th1 Responses in Crescentic GN.

Th1 cells are central pathogenic mediators of crescentic GN (cGN). Mechanisms responsible for Th1 cell downregulation, however, remain widely unknown. Recently, it was proposed that activation of the Th1-characteristic transcription factor T-bet optimizes Foxp3+ regulatory T (Treg) cells to counteract Th1-type inflammation. Because very little is known about the role of T-bet+ Treg1 cells in inflammatory diseases, we studied the function of these cells in the nephrotoxic nephritis (NTN) model of cGN. The percentage of Treg1 cells progressively increased in kidneys of nephritic wild-type mice during the course of NTN, indicating their functional importance. Notably, naïve Foxp3CrexT-betfl/fl mice, lacking Treg1 cells, showed spontaneous skewing toward Th1 immunity. Furthermore, absence of Treg1 cells resulted in aggravated NTN with selectively dysregulated renal and systemic Th1 responses. Detailed analyses of Treg cells from Foxp3CrexT-betfl/fl mice revealed unaltered cytokine production and suppressive capacity. However, in competitive cotransfer experiments, wild-type Treg cells outcompeted T-bet-deficient Treg cells in terms of population expansion and expression levels of Foxp3, indicating that T-bet expression is crucial for general Treg fitness. Additionally, T-bet-deficient Treg cells lacked expression of the Th1-characteristic trafficking receptor CXCR3, which correlated with significant impairment of renal Treg infiltration. In summary, our data indicate a new subtype of Treg cells in cGN. These Treg1 cells are characterized by activation of the transcription factor T-bet, which enhances the overall fitness of these cells and optimizes their capacity to downregulate Th1 responses by inducing chemokine receptor CXCR3 expression.

Treg17 cells are programmed by Stat3 to suppress Th17 responses in systemic lupus.

Systemic lupus erythematosus (SLE) is a complex and potentially fatal autoimmune disorder. Although Th17 cells are thought to be central mediators of SLE, mechanisms underlying their counter regulation remain largely unknown. To help define this, we studied the function of the newly defined Stat3-dependent Th17-specific regulatory T cells (Treg17). Treg-specific deletion of Stat3 was achieved by generating Foxp3(Cre) × Stat3(fl/fl) mice and SLE was induced by intraperitoneal injection of pristane. Lack of Treg17 cells in these mice caused selectively enhanced peritoneal Th17 inflammation. Importantly, Treg17 deficiency also resulted in aggravated pulmonary vasculitis with increased percentages of Th17 cells and significantly higher mortality. Similarly, 4 and 9 months after pristane injection, analysis of renal and systemic immunity showed overshooting Th17 responses in the absence of Treg17 cells, associated with the aggravation of lupus nephritis. Expression of the Th17 characteristic trafficking receptor CCR6 was strikingly reduced on Tregs of Foxp3(Cre) × Stat3(fl/fl) mice, resulting in impaired renal Treg infiltration. Thus, Stat3-induced Treg17 cells are novel antiinflammatory mediators of SLE. One mechanism enabling Treg17 cells to target pathogenic Th17 responses is shared expression of the chemokine receptor CCR6.

Overspecialized and undertrained? Patient diversity encountered by medical students during their internal medicine clerkship at a university hospital.

BACKGROUND: During the four-month internal medicine clerkship in their final year, undergraduate medical students are closely involved in patient care. Little is known about what constitutes their typical learning experiences with respect to patient diversity within the different subspecialties of internal medicine and during on call hours. METHODS: 25 final year medical students (16 female, 9 male) on their internal medicine clerkship participated in this observational single-center study. To detail the patient diversity encountered by medical students at a university hospital during their 16-week internal medicine clerkship, all participants self-reported their patient contacts in the different subspecialties and during on call hours on patient encounter cards. Patients' chief complaint, suspected main diagnosis, planned diagnostic investigations, and therapy in seven different internal medicine subspecialties and the on call medicine service were documented. RESULTS: 496 PECs were analysed in total. The greatest diversity of chief complaints (CC) and suspected main diagnoses (SMD) was observed in patients encountered on call, with the combined frequencies of the three most common CCs or SMDs accounting for only 23% and 25%, respectively. Combined, the three most commonly encountered CC/SMD accounted for high percentages (82%/63%), i.e. less diversity, in oncology and low percentages (37%/32%), i.e. high diversity, in nephrology. The percentage of all diagnostic investigations and therapies that were classified as "basic" differed between the subspecialties from 82%/94% (on call) to 37%/50% (pulmonology/oncology). The only subspecialty with no significant difference compared with on call was nephrology for diagnostic investigations. With respect to therapy, nephrology and infectious diseases showed no significant differences compared with on call. CONCLUSIONS: Internal medicine clerkships at a university hospital provide students with a very limited patient diversity in most internal medicine subspecialties. Shadowing the on call resident or shorter rotations could provide a more extended patient diversity.