Recurrent 2,8-dihydroxyadenine nephropathy: a rare but preventable cause of renal allograft failure.

Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive enzyme defect of purine metabolism that usually manifests as 2,8-dihydroxyadenine (2,8-DHA) nephrolithiasis and more rarely chronic kidney disease. The disease is most often misdiagnosed and can recur in the renal allograft. We analyzed nine patients with recurrent 2,8-DHA crystalline nephropathy, in all of whom the diagnosis had been missed prior to renal transplantation. The diagnosis was established at a median of 5 (range 1.5-312) weeks following the transplant procedure. Patients had delayed graft function (n=2), acute-on-chronic (n=5) or acute (n=1) allograft dysfunction, whereas one patient had normal graft function at the time of diagnosis. Analysis of allograft biopsies showed birefringent 2,8-DHA crystals in renal tubular lumens, within tubular epithelial cells and interstitium. Fourier transformed infrared microscopy confirmed the diagnosis in all cases, which was further supported by 2,8-DHA crystalluria, undetectable erythrocyte APRT enzyme activity, and genetic testing. With allopurinol therapy, the allograft function improved (n=7), remained stable (n=1) or worsened (n=1). At last follow-up, two patients had experienced allograft loss and five had persistent chronic allograft dysfunction. 2,8-DHA nephropathy is a rare but underdiagnosed and preventable disorder that can recur in the renal allograft and may lead to allograft loss.

CMV infection in the donor and increased kidney graft loss: impact of full HLA-I mismatch and posttransplantation CD8(+) cell reduction.

Despite a large body of literature, the impact of chronic cytomegalovirus (CMV) infection in donor on long-term graft survival remains unclear, and factors modulating the effect of CMV infection on graft survival are presently unknown. In this retrospective study of 1279 kidney transplant patients, we analyzed long-term graft survival and evolution of CD8(+) cell population in donors and recipients by CMV serology and antigenemia status. A positive CMV serology in the donor was an independent risk factor for graft loss, especially among CMV-positive recipients (R(+) ). Antigenemia was not a risk factor for graft loss and kidneys from CMV-positive donors remained associated with poor graft survival among antigenemia-free recipients. Detrimental impact of donor's CMV seropositivity on graft survival was restricted to patients with full HLA-I mismatch, suggesting a role of CD8(+) cells. In R(+) patients with positive CMV antigenemia during the first year, CD8(+) cell count did not increase at 2 years posttransplantation, in contrast to R(-) recipients. In addition, marked CD8(+) -cell decrease was a risk factor of graft failure in these patients. This study identifies HLA-I full mismatch and a decrease of CD8(+) cell count at 2 years as important determinants of CMV-associated graft loss.

Cell therapy with autologous tolerogenic dendritic cells induces allograft tolerance through interferon-gamma and epstein-barr virus-induced gene 3.

Innovative therapeutic strategies are needed to diminish the impact of harmful immunosuppression in transplantation. Dendritic cell (DC)-based therapy is a promising approach for induction of antigen-specific tolerance. Using a heart allograft model in rats, we analyzed the immunoregulatory mechanisms by which injection of autologous tolerogenic DCs (ATDCs) plus suboptimal immunosuppression promotes indefinite graft survival. Surprisingly, we determined that Interferon-gamma (IFNG), a cytokine expected to be propathogenic, was threefold increased in the spleen of tolerant rats. Importantly, its blockade led to allograft rejection [Mean Survival Time (MST) = 25.6 ± 4 days], showing that IFNG plays a critical role in immunoregulatory mechanisms triggered by ATDCs. IFNG was expressed by TCRαß(+) CD3(+) CD4(-) CD8(-) NKRP1(-) cells (double negative T cells, DNT), which accumulated in the spleen of tolerant rats. Interestingly, ATDCs specifically induced IFNG production by DNT cells. ATDCs expressed the cytokinic chain Epstein-Barr virus-induced gene 3 (EBI3), an IL-12 family member. EBI3 blockade or knock-down through siRNA completely abolished IFNG expression in DNT cells. Finally, EBI3 blockade in vivo led to allograft rejection (MST = 36.8 ± 19.7 days), demonstrating for the first time a role for EBI3 in transplantation tolerance. Taken together our results have important implications in the rationalization of DC-based therapy in transplantation as well as in the patient immunomonitoring follow-up.

Long-term allograft tolerance is characterized by the accumulation of B cells exhibiting an inhibited profile.

Numerous reports have highlighted the central role of regulatory T cells in long-term allograft tolerance, but few studies have investigated the B-cell aspect. We analyzed the B-cell response in a rat model of long-term cardiac allograft tolerance induced by a short-term immunosuppression. We observed that tolerated allografts are infiltrated by numerous B cells organized in germinal centers that are strongly regulated in their IgG alloantibody response. Moreover, alloantibodies from tolerant recipients exhibit a deviation toward a Th2 isotype and do not activate in vitro donor-type endothelial cells in a pro-inflammatory way but maintained expression of cytoprotective molecules. Interestingly, this inhibition of the B-cell response is characterized by the progressive accumulation in the graft and in the blood of B cells blocked at the IgM to IgG switch recombination process and overexpressing BANK-1 and the inhibitory receptor Fcgr2b. Importantly, B cells from tolerant recipients are able to transfer allograft tolerance. Taken together, these results demonstrate a strong regulation of the alloantibody response in tolerant recipients and the accumulation of B cells exhibiting an inhibited and regulatory profile. These mechanisms of regulation of the B-cell response could be instrumental to develop new strategies to promote tolerance.

[Isolated tracheo-oesophageal fistula in neonates]. / Fistule ceso-trachéale isolée du nouveau-né.

INTRODUCTION: Congenital isolated tracheo-oesophageal fistulae without oesophageal atresia account for about 4% of tracheo-oesophageal malformations. An Otolaryngologist, even with a paediatric practice, is unlikely to treat a lot of cases during his career. We report 3 cases and discuss the investigations and management of the fistulae. PATIENTS AND METHODS: Three neonates with an isolated congenital tracheo-oesophageal fistula were treated between 1997 and 2002. We describe their presentation, investigation and treatment. We present radiology, endoscopic and surgical images for one case. RESULTS: The mean age at diagnosis of congenital isolated fistula was 6.7 days. In retrospect, the symptoms were usually present from birth. A barium swallow had demonstrated the tracheo-oesophageal fistula in 2 infants. In all three cases the fistula was clearly visualized by tracheoscopy. The most distal fistula was 25 millimetres below the true vocal cords. The closure of the fistula was made by cervicotomy in all cases. Our results are discussed with regards to the literature. CONCLUSION: Congenital tracheo-oesophageal fistulae are rare malformations. Diagnostic delay is common. Tracheo-oesophageal endoscopy is the investigation of choice. Good results are obtained with surgery treatment via a cervical approach. The management of such fistulae requires medical teams familiar with neonatal endoscopy and cervical surgery.

[Metoclopramide and neonatal methaemoglobinemia]. / Métoclopramide et méthémoglobinémie néonatale.

We report the case of a five-day-old newborn with cyanosis. After exclusion of pulmonary and cardiac illness, methaemoglobinemia was diagnosed. Cyanosis is the first symptom of methaemoglobinaemia. Numerous causes of methaemoglobinemia have been described, with congenital and acquired forms, which are the most frequent. We discuss here the clinical features, diagnosis, and treatment of acquired methaemoglobinaemia in newborns with special emphasis on forms secondary to metoclopramide toxicity.

[Persistent dysphonia showing a laryngeal foreign body in a child]. / Dysphonie persistante révélant un corps étranger laryngé

INTRODUCTION: Inhalation of a laryngotracheobronchial foreign body is a common pediatric emergency situation. It is a source of morbidity and even mortality, especially among children under 3 years of age. CASE REPORT: A 14-month-old child presented suddenly combining bitonal dysphonia and dyspnea. Given the persistence of symptoms after 1.5 months and the normality of examinations requested by his doctor (pH, cervical ultrasonography, cervical and thoracic radiography), an ENT opinion was sought. An aerodigestive tract endoscopy was carried out in the emergency setting, finding a glottic foreign body associated with subglottic granulomas. The foreign body extraction led to the immediate disappearance of dyspnea. Dysphonia gradually improved under Budesonide aerosols. CONCLUSION: The lack of penetration syndrome in the interrogation and non specific symptoms may lead to an important diagnosis and treatment delay with dramatic consequences in case of airway foreign body. Endoscopy under general anesthesia must be practiced if there is any doubt for a thorough examination of the airways.

Disappearance of tophi in familial juvenile hyperuricemic nephropathy after kidney transplantation.

A 40-year-old man who had been on hemodialysis for 25 months due to familial juvenile hyperuricemic nephropathy (FJHN) received a kidney transplant. Biopsy of his native kidney had shown tubulo-interstitial nephropathy. Genetic analysis confirmed abnormal uromodulin expression due to a mutation in the exon 4 of the UMOD gene. He had multiple tophi on the day of transplantation, including some on his fingers. He received immunosuppressive treatment including polyclonal antilymphocyte antibodies, mycophenolate mofetil, steroids and cyclosporine and achieved excellent renal function, with serum creatinine at 13 mg/L on day 10 posttransplantation and 9.4 mg/L at 6 months. His uric acid excretion rate increased from 4.4% at day 2 posttransplantation to 7.7% 6 months after transplantation. The number and sizes of the tophi were reduced 3 months posttransplantation, and nearly disappeared at month 6. Serum uric acid level decreased slowly from 650 mumol/L before transplantation to 300 mumol/L. Reduction of tophi was probably due to the absence of the mutated UMOD gene in the transplanted kidney.

Functional compartmentalization following induction of long-term graft survival with pregraft donor-specific transfusion.

Long-term survival is achieved in rat recipients by pre-graft donor-specific blood transfusion. We characterized the immune compartments in long-term survivors and analyzed them for capacity to transfer tolerance and protect against chronic rejection. Splenocytes and spleen T cells from treated recipients transferred long-term graft survival to 100% of secondary recipients. In contrast, blood transferred graft survival to only 50% of recipients whereas blood T cells had no effect. An unaltered TCR repertoire, an increase in suppressive CD4+CD25+ T cells, a decrease in antidonor T-cell proliferative response and normal perforin-granzyme levels were the hallmarks of the spleen T cells. Blood T cells were characterized by a strongly altered CD8+ repertoire, normal CD4+CD25+ T cell number with unchanged antidonor T-cell proliferative response, an activated T-cell phenotype and an increase in perforin-granzyme levels. However, following the transfer of blood or spleen cells into secondary recipients, all grafts displayed chronic rejection. These findings provide evidence that distinct compartments play critical roles in DST recipients. Regulatory cells do not accumulate in blood, which appears to be a reservoir for cytotoxic T cells. Spleen T cells, which display a regulatory-like profile and transfer graft survival, are not able to prevent chronic rejection.

Induction of tolerance by exosomes and short-term immunosuppression in a fully MHC-mismatched rat cardiac allograft model.

Exosomes are MHC-bearing vesicles secreted by a wide array of cells. We have previously shown that donor-haplotype exosomes from bone marrow dendritic cells (DCs) injected before transplantation significantly prolong heart allograft survival in congenic and fully MHC-mismatched Lewis rats. Here we show that donor exosomes administered after transplantation are similarly able to prolong allograft survival, however, without inducing tolerance. We therefore tested the effect of exosomes combined with short-term LF 15-0195 (LF) treatment, which blocks the maturation of DCs, so that donor-MHC antigens from exosomes could be presented in a more tolerogenic environment. LF treatment does not preclude the development of a strong antidonor cellular response, and while LF, but not exosome, treatment inhibits the antidonor humoral response and decreases leukocyte graft infiltration, allografts from LF-treated recipients were either acutely or strongly chronically rejected. Interestingly, when combined with LF treatment, exosomes induced a donor-specific allograft tolerance characterized by a strong inhibition of the antidonor proliferative response. This donor-specific tolerance was transferable to naïve allograft recipients. Moreover, exosomes/LF treatment prevented or considerably delayed the appearance of chronic rejection. These results suggest that under LF treatment, presentation of donor-MHC antigens (from exosomes) can induce regulatory responses that are able to modulate allograft rejection and to induce donor-specific allograft tolerance.