Th1 responsiveness to nephritogenic antigens determines susceptibility to crescentic glomerulonephritis in mice

Th1 responsiveness to nephritogenic antigens determines susceptibility to crescentic glomerulonephritis in mice. The pattern of glomerulonephritis (GN) developing in response to a planted antigen (sheep anti-mouse GBM globulin) was compared in two strains of mice which demonstrated either a predominant Th1 (C57BL/6) or Th2 (BALB/c) response to this antigen. GN was induced with a subnephritogenic i.v. dose of sheep anti-mouse GBM globulin in mice presensitized to sheep globulin. Sensitized C57BL/6 mice showed pronounced cutaneous delayed-type hypersensitivity (DTH) following the challenge with sheep globulin, low titers of circulating anti-sheep globulin antibody and high interferon γ (IFNγ) and low interleukin 4 (IL-4) production by splenic T cells, consistent with a predominant Th1 pattern of immune response. Sensitized BALB/c mice did not develop DTH following cutaneous challenge with sheep globulin, had higher circulating anti-sheep globulin antibody titers, and showed high IL-4 and low IFNγ production by splenic T cells compared with C57BL/6 mice, consistent with a predominant Th2 response. In C57BL/6 mice, GN developing in response to sheep globulin exhibited a severe crescentic pattern with prominent glomerular T cell and macrophage influx and fibrin deposition. In vivo depletion with a monoclonal anti-CD4 antibody demonstrated that this injury was T helper cell dependent. Treatment with monoclonal anti-mouse IFNγ antibody significantly reduced glomerular injury and crescent formation and attenuated the cutaneous DTH response. GN induced by the same protocol in BALB/c mice exhibited pronounced glomerular IgG and complement deposition. Crescent formation, fibrin deposition, and glomerular T cell and macrophage infiltration were significantly less than observed in C57BL/6 mice, and injury was not T cell dependent in the effector phase. These data suggest that the pattern of glomerular injury induced by a planted antigen can be determined by the balance of T helper cell subset activation. A Th1 response induces a severe crescentic pattern of GN, which like cutaneous DTH, is T helper cell and IFNγ dependent

Fibrin independent proinflammatory effects of tissuefactor in experimental crescentic glomerulonephritis

Fibrin independent proinflammatory effects of tissue factor in experimental crescentic glomerulonephritis.BackgroundTissue factor initiated glomerular fibrin deposition is an important mediator of injury in crescentic glomerulonephritis. Recent data have suggested noncoagulant roles for tissue factor in inflammation.MethodsTo test the hypothesis that in addition to its effects in initiating coagulation, tissue factor has proinflammatory effects in glomerulonephritis, rabbits given crescentic anti-glomerular basement membrane (GBM) antibody–induced glomerulonephritis were defibrinogenated with ancrod. One group of defibrinogenated rabbits was also given anti-tissue factor antibodies. Comparisons were made between these groups, as well as a third group that was neither defibrinogenated with ancrod nor given anti-tissue factor antibodies.ResultsDefibrinogenation alone abolished glomerular fibrin deposition, reduced crescent formation, and limited renal impairment (ancrod-treated, serum creatinine 274 ± 37 μmol/L; untreated 415 ± 51 μmol/L; P < 0.01). Tissue factor inhibition in defibrinogenated rabbits resulted in further protection of renal function (creatinine 140 ± 19 μmol/L, P < 0.01) and reduced proteinuria (0.4 ± 0.2g/day, untreated 2.6 ± 0.4 g/day, P <0.01), which was significantly increased by defibrinogenation alone (ancrod-treated, 5.6 ± 1.2 g/day). Anti-tissue factor antibodies (but not defibrinogenation alone) attenuated glomerular T-cell and macrophage recruitment, and major histocompatibility complex (MHC) class II expression.ConclusionThese results demonstrate important proinflammatory effects of tissue factor in crescentic glomerulonephritis that are fibrin independent and provide in vivo evidence for tissue factor's proinflammatory effects on MHC class II expression and leukocyte accumulation

Interleukin-4 deficiency enhances Th1 responses and crescentic glomerulonephritis in mice

Interleukin-4 deficiency enhances Th1 responses and crescentic glomerulonephritis in mice. Evidence suggests that crescentic glomerulonephritis (GN) is due to T helper cell 1 (Th1) directed delayed-type hypersensitivity (DTH)-like injury. As endogenous interleukin (IL)-4, (the pivotal cytokine in Th2 responses) may attenuate Th1 responses in this disease, we compared the development of crescentic GN, induced by a planted antigen, in mice genetically deficient in IL-4 (IL-4−/−) with disease in normal mice (IL-4+/+). IL-4−/− mice developed more severe GN with increased renal impairment (CCr 35 ± 7 μl/min vs. 133 ± 14 μl/min, P < 0.002) and crescent formation (55.7 ± 8.4% vs. 4.9 ± 1.2%, P < 0.002). This was associated with increased glomerular fibrin deposition, glomerular CD4+ T cell infiltration and macrophage recruitment. Systemically, IL-4−/− mice showed an increased antigen specific Th1 response indicated by increased skin DTH, and increased IgG3 and IgG2b. Decreased IgG1 levels indicated a reduced Th2 response. These results demonstrate a protective role for endogenous IL-4 in crescentic GN. They show that IL-4 deficiency promotes crescentic glomerular injury and amplifies local and systemic Th1 responses. They support the hypothesis that crescent formation results from Th1 immune responses to antigens in the glomerulus

Measured estimates of semi-natural terrestrial NPP in Great Britain:comparison with modelled values, and dependence on atmospheric nitrogen deposition

Plant growth in nitrogen (N)-limited, unfertilised terrestrial ecosystems should respond to additional N inputs from atmospheric deposition (Ndep). We investigated this for sites in Great Britain (GB) by compiling 796 estimates of net primary productivity (NPP) from measured biomass production over the period 1932–2014, although the great majority were for 1990 onwards. The sites were largely vegetated with shrubs, grass and bracken, and had a wide range of Ndep (0.5–3.3 gN m−2 a−1 in 2000). The measured NPP estimates were compared with calculated values from the biogeochemical ecosystem model N14CP, which predicts that NPP depends strongly upon Ndep. The measured and modelled average total NPP values (gC m−2 a−1) from all data were 387 (standard deviation, SD = 193) and 377 (SD = 72) respectively. Measured and modelled averages for vegetation classes followed the sequence: broadleaved trees ~ needle-leaved trees > herbs (rough grassland + bracken) ~ shrubs. After averaging measured values for sites in individual model grid cells (5 km × 5 km) with 10 or more replicates, the measured and modelled NPP values were correlated (n = 26, r2 = 0.22, p = 0.011), with a slope close to unity. Significant linear relationships were found between measured ln NPP and cumulative Ndep for both herbs (n = 298, p = 0.021) and shrubs (n = 473, p = 0.006), with slopes comparable to those predicted with the model. The results suggest that semi-natural NPP in GB depends positively upon Ndep, in a manner that agrees quantitatively with N14CP predictions. Calculations with the model, using modelled temporal variation in Ndep, indicate that fertilisation by Ndep caused average increases in semi-natural NPP over the period 1800 to 2010 of 30% for shrubs, 71% for herbs, and 91% for broadleaved trees. Combined with previous published results for forests, our findings suggest a general and widespread vegetation response to fertilisation by Ndep

Conditional Ablation of Macrophages Halts Progression of Crescentic Glomerulonephritis

The presence of macrophages in inflamed glomeruli of rat kidney correlates with proliferation and apoptosis of resident glomerular mesangial cells. We assessed the contribution of inflammatory macrophages to progressive renal injury in murine crescentic glomerulonephritis (GN). Using a novel transgenic mouse (CD11b-DTR) in which tissue macrophages can be specifically and selectively ablated by minute injections of diphtheria toxin, we depleted renal inflammatory macrophages through days 15 and 20 of progressive crescentic GN. Macrophage depletion reduced the number of glomerular crescents, improved renal function, and reduced proteinuria. Morphometric analysis of renal tubules and interstitium revealed a marked attenuation of tubular injury that was associated with reduced proliferation and apoptosis of tubular cells. The population of interstitial myofibroblasts decreased after macrophage depletion and interstitial fibrosis also decreased. In the presence of macrophages, interstitial myofibroblasts exhibited increased levels of both proliferation and apoptosis, suggesting that macrophages act to support a population of renal myofibroblasts in a high turnover state and in matrix deposition. Finally, deletion of macrophages reduced CD4 T cells in the diseased kidney. This study demonstrates that macrophages are key effectors of disease progression in crescentic GN, acting to regulate parenchymal cell populations by modulating both cell proliferation and apoptosis

An analysis of single amino acid repeats as use case for application specific background models

Background Sequence analysis aims to identify biologically relevant signals against a backdrop of functionally meaningless variation. Increasingly, it is recognized that the quality of the background model directly affects the performance of analyses. State-of-the-art approaches rely on classical sequence models that are adapted to the studied dataset. Although performing well in the analysis of globular protein domains, these models break down in regions of stronger compositional bias or low complexity. While these regions are typically filtered, there is increasing anecdotal evidence of functional roles. This motivates an exploration of more complex sequence models and application-specific approaches for the investigation of biased regions. Results Traditional Markov-chains and application-specific regression models are compared using the example of predicting runs of single amino acids, a particularly simple class of biased regions. Cross-fold validation experiments reveal that the alternative regression models capture the multi-variate trends well, despite their low dimensionality and in contrast even to higher-order Markov-predictors. We show how the significance of unusual observations can be computed for such empirical models. The power of a dedicated model in the detection of biologically interesting signals is then demonstrated in an analysis identifying the unexpected enrichment of contiguous leucine-repeats in signal-peptides. Considering different reference sets, we show how the question examined actually defines what constitutes the 'background'. Results can thus be highly sensitive to the choice of appropriate model training sets. Conversely, the choice of reference data determines the questions that can be investigated in an analysis. Conclusions Using a specific case of studying biased regions as an example, we have demonstrated that the construction of application-specific background models is both necessary and feasible in a challenging sequence analysis situation