Giles Walters

Follicular helper T cells are required for systemic autoimmunity

Production of high-affinity pathogenic autoantibodies appears to be central to the pathogenesis of lupus. Because normal high-affinity antibodies arise from germinal centers (GCs), aberrant selection of GC B cells, caused by either failure of negative selection or enhanced positive selection by follicular helper T (TFH) cells, is a plausible explanation for these autoantibodies. Mice homozygous for the san allele of Roquin, which encodes a RING-type ubiquitin ligase, develop GCs in the absence of foreign antigen, excessive TFH cell numbers, and features of lupus. We postulated a positive selection defect in GCs to account for autoantibodies. We first demonstrate that autoimmunity in Roquinsan/san (sanroque) mice is GC dependent: deletion of one allele of Bcl6 specifically reduces the number of GC cells, ameliorating pathology. We show that Roquinsan acts autonomously to cause accumulation of TFH cells. Introduction of a null allele of the signaling lymphocyte activation molecule family adaptor Sap into the sanroque background resulted in a substantial and selective reduction in sanroque TFH cells, and abrogated formation of GCs, autoantibody formation, and renal pathology. In contrast, adoptive transfer of sanroque TFH cells led to spontaneous GC formation. These findings identify TFH dysfunction within GCs and aberrant positive selection as a pathway to systemic autoimmunity.

Interferon-γ Excess Leads to Pathogenic Accumulation of Follicular Helper T Cells and Germinal Centers

Overactivity of the germinal center (GC) pathway resulting from accumulation of follicular helper T (Tfh) cells causes autoimmunity, underscoring the need to understand the factors that control Tfh cell homeostasis. Here we have identifed posttranscriptional repression of interferon-γ (Ifng) mRNA as a mechanism to limit Tfh cell formation. By using the sanroque lupus model, we have shown that decreased Ifng mRNA decay caused excessive IFN-γ signaling in T cells and led to accumulation of Tfh cells, spontaneous GC, autoantibody formation, and nephritis. Unlike ICOS and T-bet deficiency that failed to rescue several autoimmune manifestations, interferon-γ receptor (IFN-γR) deficiency prevented lupus development. IFN-γ blockade reduced Tfh cells and autoantibodies, demonstrating that IFN-γ overproduction was required to sustain lupus-associated pathology. Increased IFN-γR signaling caused Bcl-6 overexpression in Tfh cells and their precursors. This link between IFN-γ and aberrant Tfh cell formation provides a rationale for IFN-γ blockade in lupus patients with an overactive Tfh cell-associated pathway.

Interventions for renal vasculitis in adults. A systematic review

BackgroundRenal vasculitis presents as rapidly progressive glomerulonephritis and comprises of a group of conditions characterised by acute kidney failure, haematuria and proteinuria. Treatment of these conditions involves the use of steroid and non-steroid agents with or without adjunctive plasma exchange. Although immunosuppression has been successful, many questions remain unanswered in terms of dose and duration of therapy, the use of plasma exchange and the role of new therapies. This systematic review was conducted to determine the benefits and harms of any intervention for the treatment of renal vasculitis in adults.MethodsWe searched the Cochrane Central Register of Controlled Trials, the Cochrane Renal Group Specialised Register, MEDLINE and EMBASE to June 2009. Randomised controlled trials investigating any intervention for the treatment of adults were included. Two authors independently assessed study quality and extracted data. Statistical analyses were performed using a random effects model and results expressed as risk ratio with 95% confidence intervals for dichotomous outcomes or mean difference for continuous outcomes.ResultsTwenty two studies (1674 patients) were included. Plasma exchange as adjunctive therapy significantly reduces the risk of end-stage kidney disease at 12 months (five studies: RR 0.47, CI 0.30 to 0.75). Four studies compared the use of pulse and continuous administration of cyclophosphamide. Remission rates were equivalent but pulse treatment causes an increased risk of relapse (4 studies: RR 1.79, CI 1.11 to 2.87) compared with continuous cyclophosphamide. Azathioprine has equivalent efficacy as a maintenance agent to cyclophosphamide with fewer episodes of leukopenia. Mycophenolate mofetil may be equivalent to cyclophosphamide as an induction agent but resulted in a higher relapse rate when tested against Azathioprine in remission maintenance. Rituximab is an effective remission induction agent. Methotrexate or Leflunomide are potential choices in remission maintenance therapy. Oral co-trimoxazole did not reduce relapses significantly in Wegeners granulomatosis.ConclusionsPlasma exchange is effective in patients with severe ARF secondary to vasculitis. Pulse cyclophosphamide results in an increased risk of relapse when compared to continuous oral use but a reduced total dose. Whilst cyclophosphamide is standard induction treatment, rituximab and mycophenolate mofetil are also effective. Azathioprine, methotrexate and leflunomide are effective as maintenance therapy. Further studies are required to more clearly delineate the appropriate place of newer agents within an evidence-based therapeutic strategy.

T Follicular Helper Cells in Transplantation.

The recently described T follicular helper (Tfh) cell is required for the production of high affinity antibody. After contact with follicular dendritic cells, Tfh cells move into the germinal centre and provide help to B cells both by direct B cell-T cell interaction and production of IL-21. This drives proliferation, differentiation, and affinity maturation of the B cells to produce plasma cells capable of secreting high-affinity antibody. Circulating Tfh cells are produced by movement of Tfh cells from lymph nodes after dendritic cell contact. A reduction of Tfh cell-associated molecules is linked with increased expression of other chemokine receptors to form Th1-, Th2-, and Th17-like Tfh cells. These circulating Tfh cells are able to help B cells in vitro and to move into target tissues to support antibody production. Alloantibody production is dependent on T-cell help via the indirect pathway. Antibody-mediated rejection is therefore dependent on Tfh cells. Animal data suggest that Tfh cells and B cells migrate to the allograft and are involved in alloantibody production within a tertiary lymphoid organ. There is some data supporting the same process within human allografts. The requirement for T-cell help provides a potential therapeutic target in the treatment of antibody-mediated rejection.

Systemic capillary leak syndrome: recognition prevents morbidity and mortality

Idiopathic systemic capillary leak syndrome (SCLS) is extremely rare but carries a high morbidity and mortality. The diagnosis is made clinically by a classic triad of hypotension, hypoalbuminaemia and haemoconcentration. There have been recent advances in understanding the pathophysiological basis for SCLS and in effective prophylaxis. We report a case of SCLS to increase awareness of the condition and to highlight the benefits of prophylactic intravenous immunoglobulin in this condition.

Candida tropicalis bezoar as a cause of obstructive nephropathy

A 27-year-old man presented with a 10-day history of dysuria, oliguria, and left-sided flank pain. On the day of presentation he developed hiccups. He had poorly controlled type 1 diabetes mellitus and was an active recreational intravenous drug user. He was febrile to 38.7°. Physical examination demonstrated only mild left-sided flank pain. Urine output was <10 ml/h.

Allograft adenovirus nephritis

We present an uncommon case of allograft adenovirus tubulointerstitial nephritis in a 63-year-old male 6 weeks following cadaveric renal transplantation for end-stage renal failure secondary to hypertensive nephrosclerosis. The patient presented with acute onset of fevers, dysuria, haematuria and diarrhoea with acute graft dysfunction. A renal biopsy demonstrated necrotizing tubulointerstitial nephritis with viral cytopathic changes and no evidence of rejection. Adenovirus was identified as the pathogen. Treatment involved the reduction in the patients usual immunosuppression, intravenous immunoglobulin, piperacillin–tazobactam and ganciclovir. We present the clinical and pathological findings of necrotizing adenoviral nephropathy, highlighting the importance of considering this diagnosis in renal transplant recipients presenting with interstitial nephritis in the setting of a systemic illness.

IL-27 Directly Enhances Germinal Center B Cell Activity and Potentiates Lupus in Sanroque Mice

Germinal centers (GC) give rise to high-affinity and long-lived Abs and are critical in immunity and autoimmunity. IL-27 supports GCs by promoting survival and function of T follicular helper cells. We demonstrate that IL-27 also directly enhances GC B cell function. Exposure of naive human B cells to rIL-27 during in vitro activation enhanced their differentiation into CD20+CD38+CD27lowCD95+CD10+ cells, consistent with the surface marker phenotype of GC B cells. This effect was inhibited by loss-of-function mutations in STAT1 but not STAT3. To extend these findings, we studied the in vivo effects of IL-27 signals to B cells in the GC-driven Roquinsan/san lupus mouse model. Il27ra−/−Roquinsan/san mice exhibited significantly reduced GCs, IgG2a(c)+ autoantibodies, and nephritis. Mixed bone marrow chimeras confirmed that IL-27 acts through B cell– and CD4+ T cell–intrinsic mechanisms to support GCs and alter the production of pathogenic Ig isotypes. To our knowledge, our data provide the first evidence that IL-27 signals directly to B cells promote GCs and support the role of IL-27 in lupus.

MMP2 and MMP9 associate with crescentic glomerulonephritis

Abstract Background: Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by multiple organ involvement. Lupus nephritis (LN) is a common manifestation with a wide variety of histological appearances. Matrix metalloproteinases (MMP) 2 and 9 are gelatinases capable of degrading glomerular basement membrane type IV collagen, which have been associated with LN. We examine the expression of MMP2 and MMP9 in different classes of LN. Methods: MMP2 and MMP9 expression was detected by immunohistochemistry in sections from renal biopsy specimens with class III, class IV and class V LN (total n = 31), crescentic immunoglobulin A nephropathy (n = 6), pauci-immune glomerulonephritis (n = 7), minimal change disease (n = 2), mesangiocapillary glomerulonephritis (n = 7), diabetic nephropathy (n = 12) and histologically normal controls (n = 8). Results: MMP2 and MMP9 were not expressed in all classes of LN, but were observed in LN with cellular and fibrocellular crescents. MMP2/MMP9 was expressed in cellular and fibrocellular crescents regardless of glomerulonephritis but not observed in inactive fibrous crescents or with mesangial proliferation. This suggests that MMP2 and MMP9 are involved in the development of extracapillary proliferative lesions. Conclusions: MMP2/MMP9 is expressed with active extracapillary proliferation. Further study is necessary to define whether the expression of MMP2/MMP9 reflects a role in glomerular repair after injury, a role in organ-level immune responses or a role as a marker of epithelialization.

Placebo-controlled, randomized clinical trial of high-dose cholecalciferol in renal dialysis patients: effect on muscle strength and quality of life

Abstract Background The importance of vitamin D sufficiency in deficient dialysis patients is uncertain. This study aimed to determine if high-dose cholecalciferol for 1-year affected symptoms, muscle strength, blood pressure (BP), cardiac ischaemia, parathyroid hormone, calcium or phosphate. Methods This was a randomized, double-blind, placebo-controlled trial with 1-year follow-up that enrolled dialysis patients with 25-hydroxy-vitamin D [25(OH)D] concentration <50 nmol/L. Consenting patients were randomized to 50 000 U/week oral cholecalciferol or matching placebo. Dosage was adjusted at 3- and 6-month study visits, targeting a 25(OH)D concentration >80 nmol/L. The primary objectives were to assess the effect of supplementation on renal-specific symptoms and on hand-grip strength. Symptoms were assessed using the Kidney Disease Quality of Life Short Form and muscle strength with a hand grip-strength dynamometer. Hypothesis testing was by two-group t-test and Wilcoxon rank-sum on an intention-to-treat basis. Results In all, 68 participants were randomized and received study medication. Median 12-month plasma 25(OH)D concentration was 119 nmol/L and 37 nmol/L in the cholecalciferol and placebo groups, respectively. There was no statistical difference in primary outcomes at 12 months. Mean symptom scores at 12 months were two lower in the cholecalciferol group (95% confidence interval −10 to 6) and geometric mean grip-strength was 27 kg in both groups. Symptoms, strength, BP, plasma mineral bone parameters and adverse events were not different between the groups at follow-up. Conclusions High-dose cholecalciferol in a deficient dialysis population had no effect on muscle strength or symptoms but appears safe.