Jean-Claude Aldigier

Development of a risk stratification algorithm to improve patient-centered care and decision making for incident elderly patients with end-stage renal disease.

A significant number of elderly patients die during their first 3 months of dialysis. Because dialysis can impair the quality of both life and death, a personalized care plan based on both early prognosis and patient choices is required. We developed a prognostic screening tool to identify older patients in need of specific care based on a multidisciplinary approach. Our study included 24,348 patients aged 75 years and older from the French national renal epidemiology and information network (REIN) registry who began dialysis between 1 January 2005 and 30 September 2012. Our primary outcome was overall mortality during the first 3 months of renal replacement therapy. Multivariate logistic regression was used to construct a scoring system in a random half of the cohort (training set). This score, which included age, gender, specific comorbidities, albumin levels, and mobility, was then applied to the other half (validation set). In all, 2548 patients died during the first 3 months after dialysis initiation, 22% after dialysis withdrawal. Three risk groups were identified: low risk (score under 12 points, 3-month expected mortality under 20%), intermediate risk (score from 12 to 16, mortality between 20 and 40%, 9.5% of patients) and high risk (score 17 or more, mortality over 40%, 2.5% of patients). We developed a decision-making process that classifies patients according to their risk of early death in view of their potentially imminent need for supportive care or treatment.

Crystal-storing histiocytosis with renal Fanconi syndrome: pathological and molecular characteristics compared with classical myeloma-associated Fanconi syndrome

BACKGROUND Crystal-storing histiocytosis (CSH) is a poorly described complication of monoclonal gammopathy featuring histiocyte lysosomal storage of kappa light chain (kappa LC) crystals. Although CSH is usually associated with systemic manifestations, renal involvement is uncommon. METHODS To investigate the molecular mechanisms implicated in kappa LC crystallization, we performed immunopathological and molecular studies in three patients with CSH and renal Fanconi syndrome (CSH/FS). The V kappa sequences were determined, and resulting molecular models were compared with previously reported myeloma-associated FS kappa LC sequences. RESULTS All patients presented with chronic tubulo-interstitial nephritis and renal FS with accumulation of monoclonal kappa LC crystals within proximal tubular cells. They showed peri-renal and interstitial infiltration by histiocytes containing eosinophilic crystalline inclusions (pseudo-pseudo-Gaucher cells). LC sequences were determined and assigned to their germline counterparts, in strong homology with previously reported myeloma-associated FS sequences. Comparison of CSH/FS V kappa domain 3D structures with the germline-encoded structures and those from patients with myeloma-associated FS underlined distinct hydrophobic residues exposed to the solvent in two patients, likely favouring the formation of a variant form of crystals that may further resist degradation after phagocytosis. CONCLUSION Although CSH/FS and myeloma-associated FS are closely related disorders, peculiar mutations in the V domains of CSH/FS monoclonal kappa LCs, different from those in myeloma-associated FS, may account for crystal morphology, predominant accumulation within histiocytes and multiple organ involvement in CSH.

Severe sirolimus-induced acute hepatitis in a renal transplant recipient

Sirolimus is currently used as an immunosuppressive agent in kidney transplantation due to its lack of nephrotoxicity and antiproliferative properties. However, a large number of side effects has been described with the use of m‐Tor inhibitors. Most are reversible when treatment is withdrawn. Hepatotoxicity is one of these side effects, considered as a benign condition and resulting generally in a transitory and small increase in transaminase levels. We report here, to the best of our knowledge, the first case of severe sirolimus‐induced acute hepatitis confirmed by liver biopsy, in a renal transplant recipient. This condition was completely cured in few weeks after sirolimus withdrawal.

Molecular study of an IgG1κ cryoglobulin yielding organized microtubular deposits and glomerulonephritis in the course of chronic lymphocytic leukaemia

Glomerulonephritis with organized microtubular monoclonal immunoglobulin deposits (GOMMID) and glomerulonephritis related to type I cryoglobulin are well‐known but rare complications of B cell derived chronic lymphocytic leukaemia. In these disorders, monoclonal Ig have never been studied at the molecular level. We conducted a pathological and molecular analysis in a patient with chronic lymphocytic leukaemia, glomerulonephritis and a single circulating monoclonal Ig. Unusual IgG1κ kidney deposits were observed. The heavy and light chain variable region sequences of that cryoprecipitating monoclonal Ig were characterized. Light microscopy revealed glomerulonephritis typical of cryoglobulinaemia, with neutrophil and macrophage infiltration, endocapillary hyperplasia and few protein thrombi. Electron microscopic study clearly evidenced numerous subepithelial mixed granular and organized deposits with a unique microtubular organization, reminiscent of the GOMMID. The Ig molecule sequence revealed alterations of charge and hydrophobicity potentially promoting a crystal‐like aggregation and the aggregation of microtubules.This description suggests that common mechanisms are involved in various forms of precipitation and/or deposition of complete Ig molecules, with a variable extent of organization and with a possible overlap between pathological patterns of either glomerulonephritis with microtubular deposits or type I cryoglobulinic glomerulonephritis.

CSReport: A New Computational Tool Designed for Automatic Analysis of Class Switch Recombination Junctions Sequenced by High-Throughput Sequencing.

B cells ensure humoral immune responses due to the production of Ag-specific memory B cells and Ab-secreting plasma cells. In secondary lymphoid organs, Ag-driven B cell activation induces terminal maturation and Ig isotype class switch (class switch recombination [CSR]). CSR creates a virtually unique IgH locus in every B cell clone by intrachromosomal recombination between two switch (S) regions upstream of each C region gene. Amount and structural features of CSR junctions reveal valuable information about the CSR mechanism, and analysis of CSR junctions is useful in basic and clinical research studies of B cell functions. To provide an automated tool able to analyze large data sets of CSR junction sequences produced by high-throughput sequencing (HTS), we designed CSReport, a software program dedicated to support analysis of CSR recombination junctions sequenced with a HTS-based protocol (Ion Torrent technology). CSReport was assessed using simulated data sets of CSR junctions and then used for analysis of Sμ-Sα and Sμ-Sγ1 junctions from CH12F3 cells and primary murine B cells, respectively. CSReport identifies junction segment breakpoints on reference sequences and junction structure (blunt-ended junctions or junctions with insertions or microhomology). Besides the ability to analyze unprecedentedly large libraries of junction sequences, CSReport will provide a unified framework for CSR junction studies. Our results show that CSReport is an accurate tool for analysis of sequences from our HTS-based protocol for CSR junctions, thereby facilitating and accelerating their study.

Specific impairment of proximal tubular cell proliferation by a monoclonal κ light chain responsible for Fanconi syndrome

BACKGROUND Fanconi syndrome (FS) is a rare renal disorder featuring proximal tubule dysfunction that may occur following tubular reabsorption of a monoclonal light chain (LC), in patients with multiple myeloma. FS may precede the recognition of multiple myeloma by several years. In most cases, crystalline inclusions of monoclonal κ LCs are observed within the lysosomes of proximal tubular cells (PTCs) and probably participate in their functional alteration. METHODS To investigate the mechanism implicated in proximal tubule dysfunction, we compared the effects of κ LC-CHEB obtained from a patient with myeloma-associated FS to those of control κ LC-BON obtained from a patient without evidence of FS, on the viability and proliferation of two different PTC lines. RESULTS Our data suggest that the tubular atrophy in myeloma-associated FS does not result from increased apoptosis of PTCs, but from their impaired capacity to proliferate and renew. Indeed, in vitro incubation of cultured PTCs with physiological amounts of the nephrotoxic κ LC-CHEB was sufficient to cause a depression in DNA synthesis and in cell proliferation. This effect was observed neither with control κ LC-BON nor in the absence of κ LC. CONCLUSIONS The reduced turnover of PTCs may affect tubular repair and regeneration. In addition, the reduced proliferation of myeloma cells producing the same monoclonal κ LC might explain the frequent association of FS with smoldering multiple myeloma.

IgA Structure Variations Associate with Immune Stimulations and IgA Mesangial Deposition

IgA1 mesangial deposition is the hallmark of IgA nephropathy and Henoch-Schönlein purpura, the onset of which often follows infections. Deposited IgA has been reported as polymeric, J chain associated, and often, hypogalactosylated but with no information concerning the influence of the IgA repertoire or the link between immune stimuli and IgA structure. We explored these issues in the α1KI mouse model, which produces polyclonal human IgA1 prone to mesangial deposition. Compared with mice challenged by a conventional environment, mice in a specific pathogen-free environment had less IgA deposition. However, serum IgA of specific pathogen-free mice showed more galactosylation and much lower polymerization. Notably, wild-type, α1KI, and even J chain-deficient mice showed increased polymeric serum IgA on exposure to pathogens. Strict germfree conditions delayed but did not completely prevent deposition; mice housed in these conditions had very low serum IgA levels and produced essentially monomeric IgA. Finally, comparing monoclonal IgA1 that had different variable regions and mesangial deposition patterns indicated that, independently of glycosylation and polymerization, deposition might also depend on IgA carrying specific variable domains. Together with IgA quantities and constant region post-translational modifications, repertoire changes during immune responses might, thus, modulate IgA propensity to deposition. These IgA features are not associated with circulating immune complexes and C3 deposition and are more pertinent to an initial IgA deposition step preceding overt clinical symptoms in patients.

Gammopathy with IgA mesangial deposition provides a monoclonal model of IgA nephritogenicity and offers new insights into its molecular mechanisms

BACKGROUND Henoch-Schönlein purpura (HSP) and IgA nephropathy (IgAN) are characterized by mesangial deposition of polyclonal IgA eventually showing aberrant glycosylation, affinity for mesangial cells and/or co-precipitation with antigen, bacterial peptides, autoantibodies or soluble receptors. IgA were also suggested to be negatively charged and predominantly of λ type but rarely in a monoclonal form. METHODS A gammopathy case with HSP provided us with a unique molecularly defined nephritogenic IgA1λ. Immunological analysis, biological activities, glycosylation analysis and finally IgA sequence were determined. RESULTS Compared to IgA1 from healthy subjects or IgAN patients, IgA1 CAT showed hyposialylation but no hypogalactosylation, in agreement with underexpression of sialyltransferase genes by the plasma cell clone. IgA variable domains had low pIs with negatively charged complementarity-determining regions. Weak reactivity appeared against the cationic autoantigen lactoferrin, which was, however, absent from kidney deposits. Deposition also occurred in mice upon injection of only the polymeric form of IgA1 CAT, despite whether or not co-injected with lactoferrin. CONCLUSIONS This monoclonal model of IgA nephritogenicity strongly suggests that beside hinge region glycosylation, V domains play a role in IgA stability and pathogenicity and supports the hypothesis that responses against cationic epitopes from pathogens or autoantigens may select negatively charged complementarity-determining regions prone either to bind charged structures of the mesangium or to promote by themselves IgA aggregation and deposition.

PAI-1 donor polymorphism influences long-term kidney graft survival

BACKGROUND The type 1 plasminogen activator inhibitor (PAI-1) is involved in the development of fibrosis, and its intrarenal expression is increased in interstitial fibrosis and tubular atrophy (IFTA). Moreover, a 4G/5G polymorphism of the PAI-1 gene has been described associating 4G haplotype with higher PAI-1 plasma activity. We investigated the relationship between the donor and recipient PAI-1 polymorphism and kidney graft survival. METHODS The PAI-1 genotype was determined for both the 304 donors and the 337 corresponding recipients. In recipients, PAI-1 antigen levels were also determined. We compared 4G/4G donors versus donors with other genotypes. RESULTS Donor or recipient genotype did not influence the PAI-1 plasma level in recipients. Actuarial kidney graft survival was significantly reduced in the 4G/4G donor group (107 months versus 147.5 months, P = 0.013), while recipient PAI-1 genotype did not show any influence on graft survival. Moreover, graft loss due to IFTA proved significantly higher in the 4G/4G donor group (13% versus 6%, P = 0.03). Multivariate analysis showed that the significant independent variables associated with graft loss were the donor 4G/4G genotype, acute clinical rejection and donor age. CONCLUSION Our study suggests that donor PAI-1 polymorphism influences kidney graft survival and that the donor 4G/4G genotype is an independent risk factor for graft loss. Prospective studies are needed to confirm these results.

Minimization of maintenance immunosuppressive therapy after renal transplantation comparing cyclosporine A/azathioprine or cyclosporine A/mycophenolate mofetil bitherapy to cyclosporine A monotherapy: a 10‐year postrandomization follow‐up study

Long‐term outcomes in renal transplant recipients withdrawn from steroid and submitted to further minimization of immunosuppressive regimen after 1 year are lacking. In this multicenter study, 204 low immunological risk kidney transplant recipients were randomized 14.2 ± 3.7 months post‐transplantation to receive either cyclosporine A (CsA) + azathioprine (AZA; n = 53), CsA + mycophenolate mofetil (MMF; n = 53), or CsA monotherapy (n = 98). At 3 years postrandomization, the occurrence of biopsy for graft dysfunction was similar in bitherapy and monotherapy groups (21/106 vs. 26/98; P = 0.25). At 10 years postrandomization, patients’ survival was 100%, 94.2%, and 95.8% (P = 0.25), and death‐censored graft survival was 94.9%, 94.7%, and 95.2% (P = 0.34) in AZA, MMF, and CsA groups, respectively. Mean estimated glomerular filtration rate was 70.4 ± 31.1, 60.1 ± 22.2, and 60.1 ± 19.0 ml/min/1.73 m2, respectively (P = 0.16). The incidence of biopsy‐proven acute rejection was 1.4%/year in the whole cohort. None of the patients developed polyomavirus‐associated nephropathy. The main cause of graft loss (n = 12) was chronic antibody‐mediated rejection (n = 6). De novo donor‐specific antibodies were detected in 13% of AZA‐, 21% of MMF‐, and 14% of CsA‐treated patients (P = 0.29). CsA monotherapy after 1 year is safe and associated with prolonged graft survival in well‐selected renal transplant recipient (ClinicalTrials.gov number: 980654).