Can regulatory T cells improve outcomes of sensitised patients after HLA-Ab incompatible renal transplantation: study protocol for the Phase IIa GAMECHANgER-1 trial.

BACKGROUND: Kidney transplantation is the gold-standard treatment for patients with kidney failure. However, one-third of patients awaiting a kidney transplant are highly sensitized to human leukocyte antigens (HLA), resulting in an increased waiting time for a suitable kidney, more acute and chronic rejection, and a shorter graft survival compared to non-highly sensitised patients. Current standard immunosuppression protocols do not adequately suppress memory responses, and so alternative strategies are needed. Autologous polyclonally expanded regulatory T cells (Tregs) have been demonstrated to be safe in transplant settings and could be a potential alternative to modulate memory immune alloresponses. METHODS: The aim of this trial is to determine whether adoptive transfer of autologous Tregs into HLA sensitised patients can suppress memory T and B cell responses against specific HLA antigens. This is a two-part, multi-centre, prospective clinical trial, comprising an observational phase (Part 1) aiming to identify patients with unregulated cellular memory responses to HLA (Pure HLA Proteins) followed by an interventional phase (Part 2). The first 9 patients identified as being eligible in Part 1 will undergo baseline immune monitoring for 2 months to inform statistical analysis of the primary endpoint. Part 2 is an adaptive, open labelled trial based on Simon's two-stage design, with 21 patients receiving Good Manufacturing Practice (GMP)-grade polyclonally expanded Tregs to a dose of 5-10 × 106 cells/kg body weight. The primary EP is suppression of in vitro memory responses for 2 months post-infusion. 12 patients will receive treatment in stage 1 of Part 2, and 9 patients will receive treatment in stage 2 of Part 2 if ≥ 50% patients pass the primary EP in stage 1. DISCUSSION: This is a prospective study aiming to identify patients with unregulated cellular memory responses to Pure HLA Proteins and determine baseline variation in these patterns of response. Part 2 will be an adaptive phase IIa clinical trial with 21 patients receiving a single infusion of GMP-grade polyclonally expanded Tregs in two stages. It remains to be demonstrated that modulating memory alloresponses clinically using Treg therapy is achievable. TRIAL REGISTRATION: EudraCT Number: 2021-001,664-23. REC Number: 21/SC/0253. Trial registration number ISRCTN14582152.

Ceramic vs polymeric membrane implementation for potable water treatment.

The continued technological developments and decreased purchase costs of ceramic membranes have seen increased recent interest in the technology as an alternative to the more widely used polymeric membranes. This paper assesses the relative technical, practical and economic merits of the two membrane materials in the context of potable water production from surface water sources. The work focuses on phenomena of direct technoeconomic significance, namely cleaning efficacy (manifested as permeability recovery), membrane integrity and incurred labour effort. Topics reviewed thus comprise: (a) practical comparison of the two technologies challenged with the same feedwater, (b) comparative technoeconomic analyses, (c) membrane integrity studies of polymeric membranes - incorporating aged samples extracted from operating installations, (d) sludging incidents, and (e) pilot and full-scale data. Available relevant data reveal: (a) bench-scale comparative tests do not indicate a consistent significant difference in the net permeability between the two membranes; (b) polymeric membranes are subject to a decline in both mechanical strength and permeability from the loss of the hydrophilic agent over a period of years from the action of hypochlorite used for cleaning; (c) the decreased mechanical strength with age of polymeric membranes increases the manual repair requirement and shortens membrane life, respectively impacting on labour and membrane replacement costs where the latter is also determined by the permeability; (d) the chemical and mechanical robustness of ceramic membranes permits more aggressive chemical cleaning, which then affects the chemicals consumption cost; and (e) anecdotal evidence suggests that polymeric membranes challenged with pre-coagulated surface waters may be subject to sludging, the agglomeration of solids in the membrane channels, which may also be age-related. Notwithstanding the above, data from published comparative technoeconomic studies indicate a linear relationship between the overall cost benefit and the membrane module cost ratio mitigated by the relative membrane life and operating flux.

Bioaugmentation of pilot-scale slow sand filters can achieve compliant levels for the micropollutant metaldehyde in a real water matrix.

Metaldehyde is a polar, mobile, low molecular weight pesticide that is challenging to remove from drinking water with current adsorption-based micropollutant treatment technologies. Alternative strategies to remove this and compounds with similar properties are necessary to ensure an adequate supply of safe and regulation-compliant drinking water. Biological removal of metaldehyde below the 0.1 µg•L-1 regulatory concentration was attained in pilot-scale slow sand filters (SSFs) subject to bioaugmentation with metaldehyde-degrading bacteria. To achieve this, a library of degraders was first screened in bench-scale assays for removal at micropollutant concentrations in progressively more challenging conditions, including a mixed microbial community with multiple carbon sources. The best performing strains, A. calcoaceticus E1 and Sphingobium CMET-H, showed removal rates of 0.0012 µg•h-1•107 cells-1 and 0.019 µg•h-1•107 cells-1 at this scale. These candidates were then used as inocula for bioaugmentation of pilot-scale SSFs. Here, removal of metaldehyde by A. calcoaceticus E1, was insufficient to achieve compliant water regardless testing increasing cell concentrations. Quantification of metaldehyde-degrading genes indicated that aggregation and inadequate distribution of the inoculum in the filters were the likely causes of this outcome. Conversely, bioaugmentation with Sphingobium CMET-H enabled sufficient metaldehyde removal to achieve compliance, with undetectable levels in treated water for at least 14 d (volumetric removal: 0.57 µg•L-1•h-1). Bioaugmentation did not affect the background SSF microbial community, and filter function was maintained throughout the trial. Here it has been shown for the first time that bioaugmentation is an efficient strategy to remove the adsorption-resistant pesticide metaldehyde from a real water matrix in upscaled systems. Swift contaminant removal after inoculum addition and persistent activity are two remarkable attributes of this approach that would allow it to effectively manage peaks in metaldehyde concentrations (due to precipitation or increased application) in incoming raw water by matching them with high enough degrading populations. This study provides an example of how stepwise screening of a diverse collection of degraders can lead to successful bioaugmentation and can be used as a template for other problematic adsorption-resistant compounds in drinking water purification.

First-in-human study demonstrating the safety and clinical efficacy of novel anti-IL-17A monoclonal antibody CJM112 in moderate to severe plaque psoriasis.

BACKGROUND AND OBJECTIVE: Anti-IL-17A IgG/κ monoclonal antibody CJM112 binds both IL-17A and IL-17AF. The purpose of this First-in-Human study was to assess CJM112 effects on safety and efficacy in patients with moderate to severe plaque psoriasis. METHODS: This study had two parts: single ascending doses of 5-450 mg subcutaneous (s.c.) CJM112 (SAD) and multi-dose parallel groups of CJM112 15 mg, 50 mg and 150 mg s.c. low frequency or high frequency (MD). SAD/MD were double-blind, randomized and placebo-controlled; MD also included a secukinumab 150 mg s.c. arm as an active comparator. Patients 18-65 years with moderate to severe psoriasis were included in this study. The efficacy outcome was the change in Psoriasis Area Severity Index (PASI) from baseline to Week 4 in the SAD part of the study, and from baseline to Week 12 in the MD part. RESULTS: 96 patients were enrolled in this study (SAD, n = 42; MD, n = 54). In SAD, CJM112 doses from 15 mg and above demonstrated higher PASI responses compared with placebo at Week 12. CJM112 450 mg did not add further efficacy, but efficacy duration was prolonged compared with CJM112 150 mg. CJM112 MD resulted in a dose-dependent decrease in PASI over time to Week 12. CJM112 150 mg high frequency did not exceed the effect of CJM112 150 mg low frequency and had similar efficacy to secukinumab 150 mg. The safety profile of CJM112 was as expected for an antibody targeting IL-17A/IL-17AF. CONCLUSIONS: CJM112 had clinical efficacy in moderate to severe psoriasis and was generally safe and well tolerated in the doses tested. Additional neutralization of IL-17AF did not translate to increased clinical efficacy compared with secukinumab.

Influence of granular activated carbon media properties on natural organic matter and disinfection by-product precursor removal from drinking water.

Operational and financial constraints challenge effective removal of natural organic matter (NOM), and specifically disinfection by-product (DBP) precursors, at remote and/or small sites. Granular activated carbon (GAC) is a widely used treatment option for such locations, due to its relatively low maintenance and process operational simplicity. However, its efficacy is highly dependent on the media capacity for the organic matter, which in turn depends on the media characteristics. The influence of GAC media properties on NOM/DBP precursor removal has been studied using a range of established and emerging media using both batch adsorption tests and rapid small-scale column tests. DBP formation propensity (DBPFP) was measured with reference to trihalomethanes (THMs) and haloacetic acids (HAAs). All GAC media showed no selectivity for specific removal of precursors of regulated DBPs; DBP formation was a simple function of residual dissolved organic carbon (DOC) levels. UV254 was found to be a good surrogate measurement of DBPFP for an untreated water source having a high DOC. Due to the much-reduced concentration of DBP precursors, the correlation was significantly poorer for the coagulation/flocculation-pretreateed water source. Breakthrough curves generated from the microcolumn trials revealed DOC removal and consequent DBP reduction to correlate reasonably well with the prevalence pores in the 5-10 nm range. A 3-6 fold increase in capacity was recorded for a 0.005-0.045 cm3/g change in 5-10 nm-sized pore volume density. No corresponding correlation was evident with other media pore size ranges.

The combined influence of hydrophobicity, charge and molecular weight on natural organic matter removal by ion exchange and coagulation.

Three different source waters were investigated using virgin and pre-used anion exchange resins, coagulation, and ion exchange combined with coagulation (IEX&Coagulation). The hydrophobicity, size distribution and charge of natural organic matter (NOM) were used to evaluate its removal. Dissolved organic carbon (DOC) removal by pre-used IEX resin was 67-79%. A consistent ratio of different hydrophobicity fractions was found in the removed DOC, while the proportion and quantity of the molecular weight fraction around 1 kDa was important in understanding the treatability of water. For pre-used resin, organic compounds were hypothesised to be restricted to easily accessible exchange sites. Comparatively, virgin resin achieved higher DOC removals (86-89%) as resin fouling was absent. Charge density and the proportion of the hydrophobic fraction were found to be important indicators for the specific disinfection byproduct formation potential (DBP-FP). Treatment of raw water with pre-used resin decreased the specific DBP-FP by between 2 and 43%, while the use of virgin resin resulted in a reduction of between 31 and 63%. The highest water quality was achieved when the combination of IEX and coagulation was used, reducing DOC and the specific DBP-FP well below that seen for either process alone.

Understanding the potential for selective natural organic matter removal by ion exchange.

Dissolved organic carbon (DOC) removal from a river water source was investigated using ion exchange (IEX), coagulation and membrane filtration. This research linked the variable charge characteristics of the organic compounds present in the source water with removal by IEX and coagulation. The raw water charge density fluctuated considerably (between 5.4 and 10.7 meq mgDOC-1) and controlled removal of the charge loading. Importantly, charge density was not correlated with the organic carbon concentration. The combined IEX and coagulation process reduced the specific DBP-FP (sDBP-FP) of the final water, with values as low as 18 µg mgDOC-1 for both haloacetic acids and trihalomethanes. IEX removed a particular fraction of NOM that 1) enhanced coagulation efficiency, providing increased removal of overall DOC; and 2) enabled coagulation to subsequently remove higher levels of specific components of NOM that have a high DBP-FP. The component of NOM removed by IEX that had a positive impact on coagulation was identified to be charged low molecular weight organic compounds of all hydrophobicity levels, resulting in a reduced specific DBP-FP compared to coagulation alone.

THM and HAA formation from NOM in raw and treated surface waters.

The disinfection by-product (DBP) formation potential (FP) of natural organic matter (NOM) in surface water sources has been studied with reference to the key water quality determinants (WQDs) of UV absorption (UV254), colour, and dissolved organic carbon (DOC) concentration. The data set used encompassed raw and treated water sampled over a 30-month period from 30 water treatment works (WTWs) across Scotland, all employing conventional clarification. Both trihalomethane (THM) and haloacetic acid (HAA) FPs were considered. In addition to the standard bulk WQDs, the DOC content was fractionated and analysed for the hydrophobic (HPO) and hydrophilic (HPI) fractions. Results were quantified in terms of the yield (dDBPFP/dWQD) and the linear regression coefficient R2 of the yield trend. The NOM in the raw waters was found to comprise 30-84% (average 66%) of the more reactive HPO material, with this proportion falling to 18-63% (average 50%) in the treated water. Results suggested UV254 to be as good an indicator of DBPFP as DOC or HPO for the raw waters, with R2 values ranging from 0.79 to 0.82 for THMs and from 0.71 to 0.73 for HAAs for these three determinants. For treated waters the corresponding values were significantly lower at 0.52-0.67 and 0.46-0.47 respectively, reflecting the lower HPO concentration and thus UV254 absorption and commensurately reduced precision due to the limit of detection of the analytical instrument. It is concluded that fractionation offers little benefit in attempting to discern or predict chlorinated carbonaceous DBP yield for the waters across the geographical region studied. UV254 offered an adequate estimate of DBPFP based on a mean yield of ∼2600 and ∼2800 µg per cm-1 absorbance for THMFP for the raw and treated waters respectively and ∼3800 and2900 µg cm-1 for HAAFP, albeit with reduced precision for the treated waters.

Pilot-scale spiral wound membrane assessment for THM precursor rejection from upland waters.

The outcomes of a pilot-scale study of the rejection of trihalomethanes (THMs) precursors by commercial ultrafiltration/nanofiltration (UF/NF) spiral-wound membrane elements are presented based on a single surface water source in Scotland. The study revealed the expected trend of increased flux and permeability with increasing pore size for the UF membranes; the NF membranes provided similar fluxes despite the lower nominal pore size. The dissolved organic carbon (DOC) passage decreased with decreasing molecular weight cut-off, with a less than one-third the passage recorded for the NF membranes than for the UF ones. The yield (weight % total THMs per DOC) varied between 2.5% and 8% across all membranes tested, in reasonable agreement with the literature, with the aromatic polyamide membrane providing both the lowest yield and lowest DOC passage. The proportion of the hydrophobic (HPO) fraction removed was found to increase with decreasing membrane selectivity (increasing pore size), and THM generation correlated closely (R2 = 0.98) with the permeate HPO fractional concentration.

New Insights Into Roles of Ubiquitin Modification in Regulating Plastids and Other Endosymbiotic Organelles.

Recent findings have revealed important and diverse roles for the ubiquitin modification of proteins in the regulation of endosymbiotic organelles, which include the primary plastids of plants as well as complex plastids: the secondary endosymbiotic organelles of cryptophytes, alveolates, stramenopiles, and haptophytes. Ubiquitin modifications have a variety of potential consequences, both to the modified protein itself and to cellular regulation. The ubiquitin-proteasome system (UPS) can target individual proteins for selective degradation by the cytosolic 26S proteasome. Ubiquitin modifications can also signal the removal of whole endosymbiotic organelles, for example, via autophagy as has been well characterized in mitochondria. As plastids must import over 90% of their proteins from the cytosol, the observation that the UPS selectively targets the plastid protein import machinery is particularly significant. In this way, the UPS may influence the development and interconversions of different plastid types, as well as plastid responses to stress, by reconfiguring the organellar proteome. In complex plastids, the Symbiont-derived ERAD-Like Machinery (SELMA) has coopted the protein transport capabilities of the ER-Associated Degradation (ERAD) system, whereby misfolded proteins are retrotranslocated from ER for proteasomal degradation, uncoupling them from proteolysis: SELMA components have been retargeted to the second outermost plastid membrane to mediate protein import. In spite of this wealth of new information, there still remain a large number of unanswered questions and a need to define the roles of ubiquitin modification further in the regulation of plastids.

The Nottingham Prognostic Index: five- and ten-year data for all-cause survival within a screened population.

INTRODUCTION: The Nottingham Prognostic Index (NPI) is an established prognostication tool in the management of breast cancers (BCs). Latest ten-year survival data have demonstrated an improved outlook for each NPI category and the latest UK five- and ten-year survival from BC has been reported to be 85% and 77%, respectively. We compared survival of each NPI category for BCs diagnosed within the national breast screening service in Wales (Breast Test Wales (BTW)) to the latest data, and reviewed its validity in unselected cases within a screened population. METHODS: All women screened between 1998 and 2001 within BTW were included. The NPI score for each cancer was calculated using the size, nodal status, and grade of the primary tumour. Survival data (all-cause) were calculated after ten years of follow-up. RESULTS: In the three-year screening period, 199,082 women were screened. A total of 1,712 cancers were diagnosed, and 1,546 had data available for calculating the NPI. Overall five-year and ten-year survival was 94% and 82%, respectively. CONCLUSIONS: Overall five-year and ten-year survival (all-cause) has improved even when compared with UK data for BC-specific survival. We found that the NPI remains valid for BC treatment, and that our data provide a reference for updating the all-cause survival of women diagnosed with BCs within a screened population.

Removal of phosphorus from trickling filter effluent by electrocoagulation.

As regulatory requirements for contaminants in wastewater discharged to the environment get stricter, alternative or additional treatment processes to those already being used are necessary. One contaminant of particular concern associated with discharging treated municipal wastewater to a receiving water body is phosphorus (P). A continuous scale electrocoagulation (EC) system was investigated as an alternative to conventional chemical addition for P removal from municipal wastewater. The EC process was optimized for iron dose delivery by changing the electrical current, electrode spacing and the reactor contact time, and a comparison was made with conventional ferric dosing through jar testing. Results showed that EC could achieve P removal to meet a P consent of 1 mg L⁻¹ at a dose of 154 mg L⁻¹ Fe. The process was shown to provide a supplementary benefit for chemical and biological oxygen demand removal of 86% and 82%, respectively, but gave no significant removal of other sanitary pollutants. When compared directly with conventional iron dosing, EC required approximately twice the iron dose. When electrical costs were also factored into the comparison, EC was shown to be approximately double the cost of conventional dosing and at present is not a feasible alternative to conventional coagulation using ferric chloride.

The incidence and 10-year survival of interval breast cancers in Wales.

AIM: To evaluate the number of interval cancers (IC) within one screening cycle and the overall 10-year survival of IC, including its four main classifications, and compare that to screen-detected cancers (SDC). MATERIALS AND METHODS: Within Breast Test Wales (BTW), all SDC between the years 1998 and 2001 were included. IC that occurred between 1998 and 2003 that had undergone screening between the years 1998 and 2001 were also included. These IC were classified into true interval (TI), false negative (FN), occult cancer (OCC), and unclassified cancer (UCC). BTW received notification of all deaths of women that had undergone screening; thus, the 10-year all-cause survival rate was calculated from the date of diagnosis and death. RESULTS: During the study period, 199,082 women attended screening. Of these, 1020 (0.51%) women had SDC and 692 (0.38%) women developed IC. Of the 692 IC, 391 (57.8%) were TI, 120 (17.7%) were FN, 68 (10%) were OCC, and 98 (14.5%) were UCC; 15 (2.2%) were not classified. After a 10-year follow-up period, the 10-year survival rate (all-cause) for SDC was 81.6%, overall for all of IC was 72.4% (OR = 1.67, p < 0.001), TI was 77.5% (OR = 1.00, p = 0.99), FN was 55% (OR = 2.36, p < 0.001), OCC was 54.4% (OR = 3.17, p < 0.001), and UCC was 87.8% (OR = 0.61, p = 0.19). CONCLUSIONS: The overall 10-year survival of IC was significantly different to SDC. However, within this, the prognosis of TI was similar to SDC, whereas FN and OCC had significantly worse long-term survival. Further research is required to identify the underlying cause of poor survival of FN and OCC.

Coagulant Recovery from Water Treatment Residuals: A Review of Applicable Technologies.

Conventional water treatment consumes large quantities of coagulant and produces even greater volumes of sludge. Coagulant recovery (CR) presents an opportunity to reduce both the sludge quantities and the costs they incur, by regenerating and purifying coagulant before reuse. Recovery and purification must satisfy stringent potable regulations for harmful contaminants, while remaining competitive with commercial coagulants. These challenges have restricted uptake and lead research towards lower-gain, lower-risk alternatives. This review documents the context in which CR must be considered, before comparing the relative efficacies and bottlenecks of potential technologies, expediting identification of the major knowledge gaps and future research requirements.

Laminar flow reduces cases of surgical site infections in vascular patients.

INTRODUCTION: Numerous strategies are employed routinely in an effort to lower rates of surgical site infections (SSIs). A laminar flow theatre environment is generally used during orthopaedic surgery to reduce rates of SSIs. Its role in vascular surgery, especially when arterial bypass grafts are used, is unknown. METHODS: A retrospective review of a prospectively maintained database was undertaken for all vascular procedures performed by a single consultant over a one-year period. Cases were performed, via random allocation, in either a laminar or non-laminar flow theatre environment. Demographic data, operative data and evidence of postoperative SSIs were noted. A separate subgroup analysis was undertaken for patients requiring an arterial bypass graft. Univariate and multivariate logistical regression was undertaken to identify significant factors associated with SSIs. RESULTS: Overall, 170 procedures were analysed. Presence of a groin incision, insertion of an arterial graft and a non-laminar flow theatre were shown to be predictive of SSIs in this cohort. In the subgroup receiving arterial grafts, only a non-laminar flow theatre environment was shown to be predictive of an SSI. CONCLUSIONS: This study suggests that laminar flow may reduce incidences of SSI, especially in the subgroup of patients receiving arterial grafts.

Lie Markov models.

Recent work has discussed the importance of multiplicative closure for the Markov models used in phylogenetics. For continuous-time Markov chains, a sufficient condition for multiplicative closure of a model class is ensured by demanding that the set of rate-matrices belonging to the model class form a Lie algebra. It is the case that some well-known Markov models do form Lie algebras and we refer to such models as "Lie Markov models". However it is also the case that some other well-known Markov models unequivocally do not form Lie algebras (GTR being the most conspicuous example). In this paper, we will discuss how to generate Lie Markov models by demanding that the models have certain symmetries under nucleotide permutations. We show that the Lie Markov models include, and hence provide a unifying concept for, "group-based" and "equivariant" models. For each of two and four character states, the full list of Lie Markov models with maximal symmetry is presented and shown to include interesting examples that are neither group-based nor equivariant. We also argue that our scheme is pleasing in the context of applied phylogenetics, as, for a given symmetry of nucleotide substitution, it provides a natural hierarchy of models with increasing number of parameters. We also note that our methods are applicable to any application of continuous-time Markov chains beyond the initial motivations we take from phylogenetics.

The algebra of the general Markov model on phylogenetic trees and networks.

It is known that the Kimura 3ST model of sequence evolution on phylogenetic trees can be extended quite naturally to arbitrary split systems. However, this extension relies heavily on mathematical peculiarities of the associated Hadamard transformation, and providing an analogous augmentation of the general Markov model has thus far been elusive. In this paper, we rectify this shortcoming by showing how to extend the general Markov model on trees to include incompatible edges; and even further to more general network models. This is achieved by exploring the algebra of the generators of the continuous-time Markov chain together with the "splitting" operator that generates the branching process on phylogenetic trees. For simplicity, we proceed by discussing the two state case and then show that our results are easily extended to more states with little complication. Intriguingly, upon restriction of the two state general Markov model to the parameter space of the binary symmetric model, our extension is indistinguishable from the Hadamard approach only on trees; as soon as any incompatible splits are introduced the two approaches give rise to differing probability distributions with disparate structure. Through exploration of a simple example, we give an argument that our extension to more general networks has desirable properties that the previous approaches do not share. In particular, our construction allows for convergent evolution of previously divergent lineages; a property that is of significant interest for biological applications.

Quality control in urodynamics and the role of software support in the QC procedure.

AIMS: This article aims to identify quality control (QC) best practice, to review published QC audits in order to identify how closely good practice is followed, and to carry out a market survey of the software features that support QC offered by urodynamics machines available in the UK. METHODS AND RESULTS: All UK distributors of urodynamic systems were contacted and asked to provide information on the software features relating to data quality of the products they supply. The results of the market survey show that the features offered by manufacturers differ greatly. Automated features, which can be turned off in most cases, include: cough recognition, detrusor contraction detection, and high pressure alerts. There are currently no systems that assess data quality based on published guidelines. A literature review of current QC guidelines for urodynamics was carried out; QC audits were included in the literature review to see how closely guidelines were being followed. This review highlights the fact that basic QC is not being carried out effectively by urodynamicists. CONCLUSION: Based on the software features currently available and the results of the literature review there is both the need and capacity for a greater degree of automation in relation to urodynamic data quality and accuracy assessment. Some progress has been made in this area and certain manufacturers have already developed automated cough detection.

Soil [N] modulates soil C cycling in CO2-fumigated tree stands: a meta-analysis.

Under elevated atmospheric CO(2) concentrations, soil carbon (C) inputs are typically enhanced, suggesting larger soil C sequestration potential. However, soil C losses also increase and progressive nitrogen (N) limitation to plant growth may reduce the CO(2) effect on soil C inputs with time. We compiled a data set from 131 manipulation experiments, and used meta-analysis to test the hypotheses that: (1) elevated atmospheric CO(2) stimulates soil C inputs more than C losses, resulting in increasing soil C stocks; and (2) that these responses are modulated by N. Our results confirm that elevated CO(2) induces a C allocation shift towards below-ground biomass compartments. However, the increased soil C inputs were offset by increased heterotrophic respiration (Rh), such that soil C content was not affected by elevated CO(2). Soil N concentration strongly interacted with CO(2) fumigation: the effect of elevated CO(2) on fine root biomass and -production and on microbial activity increased with increasing soil N concentration, while the effect on soil C content decreased with increasing soil N concentration. These results suggest that both plant growth and microbial activity responses to elevated CO(2) are modulated by N availability, and that it is essential to account for soil N concentration in C cycling analyses.