Expression of Class II Human Leukocyte Antigens on Human Endothelial Cells Shows High Interindividual and Intersubclass Heterogeneity.

SIGNIFICANCE STATEMENT: Donor-specific antibodies against class II HLA are a major cause of chronic kidney graft rejection. Nonetheless, some patients presenting with these antibodies remain in stable histological and clinical condition. This study describes the use of endothelial colony-forming cell lines to test the hypothesis of the heterogeneous expression of HLA molecules on endothelial cells in humans. Flow cytometry and immunofluorescence staining revealed substantial interindividual and interlocus variability, with HLA-DQ the most variable. Our data suggest that the expression of HLA class II is predicted by locus. The measurement of endothelial expression of HLA class II in the graft could present a novel paradigm in the evaluation of the alloimmune risk in transplantation and certain diseases. BACKGROUND: HLA antigens are important targets of alloantibodies and allospecific T cells involved in graft rejection. Compared with research into understanding alloantibody development, little is known about the variability in expression of their ligands on endothelial cells. We hypothesized individual variability in the expression of HLA molecules. METHODS: We generated endothelial colony forming cell lines from human peripheral blood mononuclear cells ( n =39). Flow cytometry and immunofluorescence staining were used to analyze the cells, and we assessed the relationship between HLA-DQ expression and genotype. Two cohorts of kidney transplant recipients were analyzed to correlate HLA-DQ mismatches with the extent of intragraft microvascular injury. RESULTS: Large variability was observed in the expression of HLA class II antigens, not only between individuals but also between subclasses. In particular, HLA-DQ antigens had a low and heterogeneous expression, ranging from 0% to 85% positive cells. On a within-patient basis, this expression was consistent between endothelial cell colonies and antigen-presenting cells. HLA-DQ5 and -DQ6 were associated with higher levels of expression, whereas HLA-DQ7, -DQ8, and -DQ9 with lower. HLA-DQ5 mismatches among kidney transplant recipients were associated with significant increase in graft microvascular. CONCLUSION: These data challenge the current paradigm that HLA antigens, in particular HLA class II, are a single genetic and post-translational entity. Understanding and assessing the variability in the expression of HLA antigens could have clinical monitoring and treatment applications in transplantation, autoimmune diseases, and oncology.

Discovery and Validation of a Urinary Exosome mRNA Signature for the Diagnosis of Human Kidney Transplant Rejection.

BACKGROUND: Developing a noninvasive clinical test to accurately diagnose kidney allograft rejection is critical to improve allograft outcomes. Urinary exosomes, tiny vesicles released into the urine that carry parent cells' proteins and nucleic acids, reflect the biologic function of the parent cells within the kidney, including immune cells. Their stability in urine makes them a potentially powerful tool for liquid biopsy and a noninvasive diagnostic biomarker for kidney-transplant rejection. METHODS: Using 192 of 220 urine samples with matched biopsy samples from 175 patients who underwent a clinically indicated kidney-transplant biopsy, we isolated urinary exosomal mRNAs and developed rejection signatures on the basis of differential gene expression. We used crossvalidation to assess the performance of the signatures on multiple data subsets. RESULTS: An exosomal mRNA signature discriminated between biopsy samples from patients with all-cause rejection and those with no rejection, yielding an area under the curve (AUC) of 0.93 (95% CI, 0.87 to 0.98), which is significantly better than the current standard of care (increase in eGFR AUC of 0.57; 95% CI, 0.49 to 0.65). The exosome-based signature's negative predictive value was 93.3% and its positive predictive value was 86.2%. Using the same approach, we identified an additional gene signature that discriminated patients with T cell-mediated rejection from those with antibody-mediated rejection (with an AUC of 0.87; 95% CI, 0.76 to 0.97). This signature's negative predictive value was 90.6% and its positive predictive value was 77.8%. CONCLUSIONS: Our findings show that mRNA signatures derived from urinary exosomes represent a powerful and noninvasive tool to screen for kidney allograft rejection. This finding has the potential to assist clinicians in therapeutic decision making.

[Thrombotic microangiopathy and cancer]. / Microangiopathie thrombotique et cancer.

Thrombotic microangiopathy (TMA) is a group of disorders characterized by mechanical hemolytic anemia with thrombocytopenia and an ischemic organic lesion of variable and potentially fatal importance affecting mostly the kidneys and the brain with histologically a disseminated and occlusive microvasculopathy. The incidence of TMA represents 15% of acute kidney failure in oncological setting, largely due to the introduction of anti-angiogenic agents over the past decade. It may be more rarely related to cancer itself. The iatrogenic TMA can be classified into 2 types: The type I, secondary to chemotherapy (mitomycinC, gemcitabine), exposes to a chronic dose-dependent renal injury as well as an increase in morbidity and mortality; iatrogenic type II, secondary to anti-angiogenic agents', results in a dose-independent renal involvement and renal functional recovery is usual when the drug is discontinued. There is no randomized controlled trial to establish EBM-type management in TMA support. However, complement activation pathways and regulatory factors analyses allowed us to understand the mechanisms of endothelial lesions. As a result, the current trend includes the use of immunosuppressive agents in recurrent or plasmapheresis-refractory MAT.

The renal effects of ALK inhibitors.

Anaplastic lymphoma kinase 1 (ALK-1) is a member of the insulin receptor tyrosine kinase family. In clinical practice, three small molecule inhibitors of ALK-1 are used, namely crizotinib, ceritinib and alectinib. Several more agents are in active pre-clinical and clinical studies. Crizotinib is approved for the treatment of advanced ALK-positive non-small cell lung cancer (NSCLC). According to the package insert and published literature, treatment with crizotinib appears to be associated with kidney failure as well as an increased risk for the development and progression of renal cysts. In addition, this agent is associated with development of peripheral edema and rare electrolyte disorders. This review focuses on the adverse renal effects of Crizotinib in clinical practice.

[Lenalidomide nephrotoxicity]. / Néphrotoxicité du lénalidomide.

The introduction of lenalidomide into the therapeutic arsenal of hematologic malignancies has represented an important step forward in the management of multiple myeloma. However, its use is associated with several toxicities including kidney injury. The present review examines the drug's pharmacokinetics, discusses the main adverse renal effects that are associated with lenalidomide treatment, and makes recommendations for dosage adjustment in patients with underlying renal impairment.