Multidisciplinary Lupus Nephritis Clinic Reduces Time to Renal Biopsy and Improves Care Quality.

OBJECTIVE: Patients with lupus nephritis (LN) have a 26-fold higher mortality rate compared with their peers. Kidney biopsy, the gold standard diagnostic method for LN, may have an average wait time of more than 50 days. Other gaps in quality process measures during LN visits have also been reported. A subspecialty multidisciplinary clinic (MDC) can provide better care and quality in LN; therefore, we aimed to examine how an LN MDC impacted time to biopsy, time to treatment, and other quality measures. METHODS: We included all validated patients with LN who underwent diagnostic kidney biopsies between the 2011 to 2017 pre-MDC period and the 2018 to 2020 post-MDC period. We compared time to biopsy and treatment and quality measures between the two periods and examined factors associated with timely LN diagnosis, defined as a biopsy within 21 days. RESULTS: During the pre- and post-MDC periods, 53 and 21 patients with LN underwent a diagnostic biopsy, respectively. We found a decrease in the median time to biopsy from 26 days to 16 days after starting the LN clinic (P = 0.014). Beyond clinical factors, the presence of social factors, such as being of a non-White race and having food insecurity, were associated with 54% lower odds of timely diagnosis (adjusted Hazards Ratio [aHR] = 0.46; 95% confidence interval: 0.22-0.93; P = 0.031). We found higher odds of quality measure performance during the post- versus pre-MDC period. CONCLUSION: Wait times to diagnose LN decreased by 40% and higher quality measure performance was noted after establishing an LN MDC. Systemic and social barriers predicted delays in diagnosis that may be addressed by MDCs.

Macrophages in Transplantation: A Matter of Plasticity, Polarization, and Diversity.

Macrophages have emerged at the forefront of research in immunology and transplantation because of recent advances in basic science. New findings have illuminated macrophage populations not identified previously, expanded upon traditional macrophage phenotypes, and overhauled macrophage ontogeny. These advances have major implications for the field of transplant immunology. Macrophages are known to prime adaptive immune responses, perpetuate T-cell-mediated rejection and antibody-mediated rejection, and promote allograft fibrosis. In this review, macrophage phenotypes and their role in allograft injury of solid organ transplants will be discussed with an emphasis on kidney transplantation. Additionally, consideration will be given to the prospect of manipulating macrophage phenotypes as cell-based therapy. Innate immunity and macrophages represent important players in allograft injury and a promising target to improve transplant outcomes.

Association of Renal Arteriosclerosis With Atherosclerotic Cardiovascular Disease Risk in Lupus Nephritis.

OBJECTIVE: Lupus nephritis (LN) predicts a 9-fold higher atherosclerosis cardiovascular disease (ASCVD) risk, highlighting the urgent need to target ASCVD prevention. Studies in IgA nephropathy reported that severe renal arteriosclerosis (r-ASCL) in diagnostic biopsies strongly predicted ASCVD risk. We recently found that 50% of LN pathology reports overlooked r-ASCL reporting, which could explain prior negative LN ASCVD risk studies. The present study was undertaken to examine associations between a composite of reported and overread r-ASCL and ASCVD events in LN. METHODS: Data were abstracted from all LN patients who underwent diagnostic biopsy between 1994 and 2017, including demographic information, ASCVD risk factors, and pathology reports at the time of LN diagnosis. We manually validated all incident ASCVD events. We overread 25% of the biopsies to grade r-ASCL using the Banff criteria. We supplemented the overread r-ASCL grade, when available, to determine the composite of reported and overread r-ASCL grade. RESULTS: Among 189 incident LN patients, 78% were female, 73% White, and the median age was 25 years. Overall, 31% had any reported r-ASCL, and 7% had moderate-to-severe r-ASCL. After incorporating systematically re-examined r-ASCL grade, the prevalence of any and moderate-to-severe r-ASCL increased to 39% and 12%, respectively. We found 22 incident ASCVD events over 11 years of follow-up. Using a composite of reported and overread r-ASCL grade, we found that severe r-ASCL in diagnostic LN biopsies was associated with 9-fold higher odds of ASCVD. CONCLUSION: Severe r-ASCL can predict ASCVD in LN; therefore, larger studies are required to systematically report r-ASCL and examine ASCVD associations.

Natural antibody and complement activation characterize patients with idiopathic nephrotic syndrome.

Focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) are common forms of idiopathic nephrotic syndrome. The causes of these diseases are incompletely understood, but the response of patients to immunosuppressive therapies suggests that their pathogenesis is at least in part immune mediated. Preclinical and clinical research indicates that activation of the classical pathway of complement contributes to glomerular injury in FSGS. Glomerular IgM deposits are also prominent in some patients, raising the possibility that IgM is a trigger of classical pathway activation. In the present study, we examined the pattern of complement activation in the glomeruli and plasma of patients with nephrotic syndrome. We also tested whether patients with FSGS and MCD have elevated levels of natural IgM reactive with epitopes on glomerular endothelial cells and cardiolipin. We found evidence of classical pathway activation in patients with idiopathic nephrotic syndrome compared with healthy control subjects. We also detected higher levels of self-reactive IgM to both targets. Based on these results, IgM and classical pathway activation may contribute to disease pathogenesis in some patients with FSGS and MCD.NEW & NOTEWORTHY IgM is detected in biopsies from some patients with nephrotic syndrome, although this has been attributed to passive trapping of the protein. We found, however, that IgM colocalizes with complement activation fragments in some glomeruli. We also found that affected patients had higher levels of IgM reactive to glomerular endothelial cell epitopes. Thus, IgM activates the complement system in the glomeruli of some patients with nephrotic syndrome and may contribute to injury.

High Burden of Premature Arteriosclerosis on Renal Biopsy Results in Incident Lupus Nephritis.

OBJECTIVE: Cardiovascular disease (CVD) is accelerated in patients with systemic lupus erythematosus and lupus nephritis (LN). Despite the literature suggesting that renal arteriosclerosis predicts CVD in other glomerulonephritis diseases, arteriosclerosis grading and reporting might be particularly overlooked in LN biopsies. Our objective was to examine the burden of renal arteriosclerosis in LN and to assess whether arteriosclerosis is underreported in LN biopsies. METHODS: We identified all patients with LN undergoing kidney biopsy between 1994 and 2017 at an academic center. We interpreted LN biopsy reports to classify the Banff categories of absent, mild, moderate, or severe renal arteriosclerosis. The prevalence of renal arteriosclerosis was compared with the prevalence published for age-matched healthy peers, and predictors of arteriosclerosis were examined. We overread biopsies for Banff renal arteriosclerosis grading and compared to pathology reports. RESULTS: Among 189 incident patients with LN, renal arteriosclerosis prevalence was 2 decades earlier compared to their healthy peers, affecting 40% of patients ages 31-39 years with LN compared to 44% of healthy peers ages 50-59 years. A multivariable analysis showed a 3-fold higher odds of renal arteriosclerosis in patients ages ≥30 years with LN. LN chronicity on biopsy results predicted a 4-fold higher odds of renal arteriosclerosis. The overreads determined that 50% of standard LN biopsy reports missed reporting the presence or absence of renal arteriosclerosis. CONCLUSION: Renal arteriosclerosis is accelerated by 2 decades in patients with LN compared to their healthy peers and is overlooked by pathologists in half of the routine biopsy reports. We propose incorporating Banff renal arteriosclerosis grading in all LN biopsy reports.

B-cell Deficiency Attenuates Transplant Glomerulopathy in a Rat Model of Chronic Active Antibody-mediated Rejection.

BACKGROUND: Transplant glomerulopathy (TG) is a pathological feature of chronic active antibody-mediated rejection (cAMR) and is associated with renal allograft failure. The specific role of B cells in the pathogenesis of TG is unclear. METHODS: We used a minor mismatched rat kidney transplant model with B cell-deficient recipients, generated by clustered regularly interspaced short palindromic repeats/Cas9 technology, to investigate the impact of B-cell depletion on the pathogenesis of TG. We hypothesized that B-cell deficiency would prevent TG in the rat kidney transplant model of cAMR. Treatment groups included syngeneic, allogeneic, sensitized allogeneic, and B cell-deficient allogeneic transplant recipients. RESULTS: B cell-deficient recipients demonstrated reduced TG lesions, decreased microvascular inflammation, reduced allograft infiltrating macrophages, and reduced interferon gamma transcripts within the allograft. Allograft transcript levels of interferon gamma, monocyte chemoattractant protein-1, and interleukin-1ß correlated with numbers of intragraft macrophages. B cell-deficient recipients lacked circulating donor-specific antibodies and had an increased splenic regulatory T-cell population. CONCLUSIONS: In this model of cAMR, B-cell depletion attenuated the development of TG with effects on T cell and innate immunity.

Long-term outcomes in kidney transplant recipients with end-stage kidney disease due to anti-glomerular basement membrane disease.

Anti-glomerular basement membrane (GBM) disease causes rapidly progressive glomerulonephritis and end-stage kidney disease (ESKD). Studies of post-transplant outcomes in patients with ESKD due to anti-GBM disease in the United States are lacking. To better characterize outcomes of transplant recipients with a history of anti-GBM disease, we examined patient survival and graft survival among recipients with anti-GBM disease compared with IgA nephropathy at a single center in the United States. We analyzed patient survival, graft survival, disease recurrence, and malignancy rates for kidney transplant recipients with ESKD due to biopsy-proven anti-GBM disease who underwent kidney transplantation at our center between 1994 and 2015. 26 patients with biopsy-proven anti-GBM disease and 314 patients with IgAN underwent kidney transplantation from 1994 to 2015. The incidence of graft loss was 6.2 per 100 person-years for anti-GBM disease, which was similar to IgAN (4.08 per 100 person-years, p = .09). Patient mortality for anti-GBM was 0.03 per 100 person-years, similar to IgAN (0.02 per 100 person-years, p = .12). Disease recurrence occurred in one of the 26 anti-GBM patients. Four out of 26 patients (15%) developed malignancy, most commonly skin cancer. Long-term graft and patient survival for patients with ESKD due to anti-GBM was similar to IgAN after kidney transplantation.

Isolation, purification, and conditional immortalization of murine glomerular endothelial cells of microvascular phenotype.

Glomerular endothelial cells (GEnC) are a specialized microvascular subset of endothelial cells that, when injured, result in many types of diseases within the kidney. Thus, techniques to study GEnC in a cell culture system are important to investigate mechanisms of GEnC injury. Studies of endothelial cell function in culture have predominately relied on using macrovascular endothelial cells from vascular areas other than the glomerulus. Over the last 15 years, glomerular endothelial cells lines have been created but were isolated by targeting cells expressing CD31. Some studies identified endothelial cells isolated from the microvasculature do not express CD31 and some suggest that CD31+ cells are phenotypically different than endothelial cells found in capillaries. Here we detail our method of isolation, purification, and conditional immortalization of mouse glomerular endothelial cells targeting endothelial cells that do not express CD31.•This method allows for isolation, purification, and conditional immortalization of glomerular endothelial cells for continued passage of GEnCs beyond that of primary cell culture.•This method can be used in genetically modified mice to investigate how a modification of a specific gene or protein affects the glomerular endothelium at the cellular level.

Oxidized-ATP Attenuates Kidney Allograft Rejection By Inhibiting T-Cell, B-Cell, and Macrophage Activity.

Background: Extracellular ATP binds to purinergic receptors and promotes inflammatory responses. We tested whether oxidized ATP (oATP), P2X7 receptor antagonist can attenuate acute kidney allograft rejection. Methods: Brown Norway kidney allografts were transplanted into Lewis recipients. Three groups were defined: oATP (n=8), cyclosporine A (n=6), and no treatment (n=8). On day 7, we assessed kidney allograft survival, function, and rejection characteristics. We further determined T-cell, B-cell, and macrophage response to oATP in vivo and in vitro and examined intragraft inflammatory gene transcripts. Results: Kaplan-Meier survival analyses demonstrated significantly better graft survival rates in oATP and CsA groups compared with no treatment (P<0.05). Similarly, serum creatinine (Scr) and BUN levels were significantly lower in oATP and CsA groups (P<0.05). oATP reduced both T cell-mediated rejection and antibody-mediated rejection, inhibited B-cell and T-cell activation, and downregulated intragraft IL-6 mRNA levels (P<0.0001). In vitro, oATP prevented proliferation in mixed lymphocyte reaction assays, and inhibited macrophage P2X7R activity in a dose-dependent manner. Conclusions: Our findings suggest that oATP mitigates kidney allograft rejection by inhibiting T-cell, B-cell, and macrophage activity and indicate a potential role for the purinergic system and oATP in solid organ transplantation.

Short-term Immunopathological Changes Associated with Pulse Steroids/IVIG/Rituximab Therapy in Late Kidney Allograft Antibody Mediated Rejection.

BACKGROUND: B-cell depletion is a common treatment of antibody-mediated rejection (ABMR). We sought to determine the specific immunopathologic effects of this therapeutic approach in kidney transplantation. METHODS: This was a prospective observational study of kidney transplant recipients diagnosed with late ABMR (>3 months after transplant). Patients received treatment with pulse steroids, IVIG, and rituximab. Donor specific HLA antibodies (DSA), kidney allograft pathology, renal function, immune cell phenotypes, and 47 circulating cytokines were assessed at baseline and at three months. RESULTS: We enrolled 23 patients in this study between April 2015 and March 2019. The majority of patients were male (74%) and Caucasian (78%) with an average age of 45.6±13.8 years. ABMR was diagnosed at 6.8±5.9 years (4 months-25 years) post-transplant. Treatment was associated with a significant decline in circulating HLA class I DSA (P=0.003) and class II DSA (P=0.002) and peritubular capillaritis (ptc, P=0.04) compared to baseline. Serum creatinine, BUN, eGFR, and proteinuria (UPC) remained stable. Circulating B-cells were depleted to barely detectable levels (P≤0.001), whereas BAFF (P=0.001), APRIL (P<0.001), and IL-10 (P=0.02), levels increased significantly post-treatment. Notably, there was a significant rise in circulating CD4+ (P=0.02) and CD8+ T-cells (P=0.003). We also noted a significant correlation between circulating cytotoxic CD8+ T-cells and BAFF (P=0.05), regulatory T-cells and IL10 (P=0.002), and HLA class I DSA (P=0.005). CONCLUSIONS: Short-term pulse steroids/IVIG/rituximab therapy was associated with inhibition of ABMR (DSA and ptc), stabilization of kidney function, and increased regulatory B-cell and T-cell survival cytokines. Additional studies are needed to understand the implications of B cell-depletion on the crosstalk between T-cells, B-cells, and humoral components that regulate ABMR.

An in vitro model of antibody-mediated injury to glomerular endothelial cells: Upregulation of MHC class II and adhesion molecules.

Chronic active antibody-mediated rejection is a major cause of allograft failure in kidney transplantation. Microvascular inflammation and transplant glomerulopathy are defining pathologic features of chronic active antibody-mediated rejection and are associated with allograft failure. However, the mechanisms of leukocyte infiltration and glomerular endothelial cell injury remain unclear. We hypothesized MHC class II ligation on glomerular endothelial cells (GEnC) would result in upregulation of adhesion molecules and production of chemoattractants. A model of endothelial cell activation in the presence of antibodies to MHC classes I and II was used to determine the expression of adhesion molecules and chemokines. Murine GEnC were activated with IFNγ, which upregulated gene expression of ß2-microglobulin (MHC class I), ICAM1, VCAM1, CCL2, CCL5, and IL-6. IFNγ stimulation of GEnC increased surface expression of MHC class I, MHC class II, ICAM1, and VCAM1. Incubation with antibodies directed at MHC class I or class II did not further enhance adhesion molecule expression. Multispectral imaging flow cytometry and confocal microscopy demonstrated MHC molecules co-localized with the adhesion molecules ICAM1 and VCAM1 on the GEnC surface. GEnC secretion of chemoattractants, CCL2 and CCL5, was increased by IFNγ stimulation. CCL2 production was further enhanced by incubation with sensitized plasma. Endothelial activation induces de novo expression of MHC class II molecules and increases surface expression of MHC class I, ICAM1 and VCAM1, which are all co-localized together. Maintaining the integrity and functionality of the glomerular endothelium is necessary to ensure survival of the allograft. IFNγ stimulation of GEnC propagates an inflammatory response with production of chemokines and co-localization of MHC and adhesion molecules on the GEnC surface, contributing to endothelial cell function as antigen presenting cells and an active player in allograft injury.

Histopathological characteristics and causes of kidney graft failure in the current era of immunosuppression.

BACKGROUND: The histopathological findings on the failing kidney allograft in the modern era is not well studied. In this study, we present our experience working with kidney transplant recipients with graft failure within one year of the biopsy. AIM: To report the histopathological characteristics of failed kidney allografts in the current era of immunosuppression based on the time after transplant, cause of the end-stage renal disease and induction immunosuppressive medications. METHODS: In a single-center observational study, we characterized the histopathological findings of allograft biopsies in kidney transplant recipients with graft failure within one year after the biopsy. RESULTS: We identified 329 patients with graft failure that met the selection criteria between January 1, 2006 and December 31, 2016. The three most common biopsy findings were interstitial fibrosis and tubular atrophy (IFTA, 53%), acute rejection (AR, 43%) and transplant glomerulopathy (TG, 33%). Similarly, the three most common causes of graft failure based on the primary diagnosis were AR (40%), TG (17%), and IFTA (13%). Most grafts failed within two years of post-transplant (36%). Subsequently, approximately 10%-15% of grafts failed every two years: > 2-4 years (16%), > 4-6 years (13%), > 6-8 years (11%), > 8-10 years (9%) and > 10 years (16%). AR was the most common cause of graft failure in the first six years (48%), whereas TG was the most prevalent cause of graft failure after 6 years (32%) of transplant. CONCLUSION: In the current era of immunosuppression, AR is still the most common cause of early graft failure, while TG is the most prevalent cause of late graft failure.

The association of acute rejection vs recurrent glomerular disease with graft outcomes after kidney transplantation.

BACKGROUND: It has been shown that glomerulonephritis (GN) recurrence affects graft survival more than acute rejection. Thus, we assessed allograft survival after biopsy-confirmed diagnosis of acute rejection or recurrent GN in current era of immunosuppression. METHODS: Allograft survival following a biopsy diagnosis of acute rejection or recurrent GN was determined in adult kidney transplant recipients from 1994 to 2013. A total of 306 patients (35%) with IgA, 298 (35%) with FSGS, 177 (21%) with lupus nephritis, and 81 (9%) with membranous nephropathy were followed for a median of 6.3 years. RESULTS: Among the 862 transplant recipients with primary GN, allograft loss was similar following a biopsy diagnosis of acute rejection or recurrent glomerular disease (11.5 vs 14.2/100 person-years, P = .15). Differences in allograft survival emerged after 2.5 years following recurrent disease, with significantly higher graft failure in patients with FSGS, MN, or LN compared with IgA after recurrence of disease (16.7 vs 7.5/100 person-years, P = .05). The advantage in allograft survival for IgA patients did not achieve significance after acute rejection (P = .10 for IgA vs FSGS, MN, and LN). CONCLUSIONS: Allograft survival was similar after disease recurrence or acute rejection after kidney transplant in patients with ESRD due to GN.

Cause of End-Stage Renal Disease Is Not a Risk Factor for Cytomegalovirus Infection After Kidney Transplant.

BACKGROUND: Cytomegalovirus infection (CMV) after kidney transplantation leads to increased morbidity and mortality. Whether the cause of end-stage renal disease (ESRD) influences the risk of CMV infection post-transplant is not known. METHODS: We analyzed data from 2741 adult kidney transplant recipients from January 1993 through December 2014. The causes of ESRD included diabetes mellitus (n = 947), hypertension (n = 442), polycystic kidney disease (n = 549), and glomerulonephritis (GN) (n = 803). The primary outcome was incidence of CMV infection, defined as the first episode of detectable CMV DNA in the blood following transplant. RESULTS: Three hundred and thirty patients developed a CMV infection over a median follow-up of 4.5 years. Patients with diabetes mellitus (DM) as the cause of ESRD had a higher incidence of CMV infection post-transplant compared to patients with GN (2.37 vs 1.58/100 person-years, P < .005) whereas hypertension (HTN) and autosomal dominant polycystic kidney disease (PKD) were similar (2.17 and 2.07/100 person-years). DM was associated with a 35% higher risk of CMV infection compared to GN in unadjusted analyses [hazard ratio=1.35 [95% confidence interval 1.02-1.78], P = .04). However, after adjustment for age, the risk of CMV infection was similar in all groups (DM: age-adjusted hazard ratio 1.02 [0.78-1.39]; HTN: 0.96 (0.67-1.36); PKD: 1.08 [0.78-1.48]; compared to GN). The risk of CMV infection increased with age (adjusted hazard ratio=1.32 [1.18-1.47] for every decade of life, P < .001). CONCLUSIONS: Our study demonstrates that the cause of ESRD is not a significant risk factor for CMV infection in kidney transplant recipients once adjusted for age. Future studies are needed to identify risk factors for CMV infection to define patient-centered monitoring and prevention.

The role of complement in antibody mediated transplant rejection.

Antibody mediated transplant rejection (AMR) is a major cause of long-term allograft failure, and currently available treatments are of limited efficacy for treating the disease. AMR is caused by donor specific antibodies (DSA) that bind to antigens within the transplanted organ. DSA usually activate the classical pathway of complement within the allograft, and complement activation is believed to be an important cause of tissue injury in AMR. Several new clinical assays may improve our ability to identify patients at risk of AMR. Complement inhibitory drugs have also been tested in selected patients and in small series. Better understanding of the role of complement activation in the pathogenesis of AMR will likely improve our ability to diagnose the disease and to develop novel treatments.

Glomerular C3 Deposition Is an Independent Risk Factor for Allograft Failure in Kidney Transplant Recipients With Transplant Glomerulopathy.

INTRODUCTION: Transplant glomerulopathy (TG) becomes increasingly prevalent in kidney transplant recipients over time, and it is strongly associated with allograft failure. To date, our prognostic biomarkers and understanding of the processes of immunologic injury in TG are limited. METHODS: This is a retrospective cohort analysis of kidney transplant recipients with TG (double contours of the glomerular basement membrane as defined by the chronic glomerulopathy score). Glomerular deposition of the complement protein C3 was determined, and its association with allograft survival was analyzed by Cox regression analysis. RESULTS: Of the 111 patients with TG, 72 (65%) had allograft failure, with a median follow-up time of 3 years from biopsy diagnosis of TG. C3-positive compared to C3-negative patients did not differ with respect to cause of end-stage renal disease, induction or maintenance immunosuppression, or sensitization. A greater proportion of patients with glomerular C3 deposition developed allograft failure compared to those with no C3 deposition (78% vs. 55%, P = 0.01). C3 deposition was independently associated with allograft failure in multivariate analyses (adjusted hazard ratio [HR] = 1.38, 95% confidence interval [CI] = 1.13-1.69, P = 0.002). There was no association between C4d or C1q deposition and allograft failure. Chronicity score was also associated with allograft failure in multivariate analysis (adjusted HR 1.26, 95% CI 1.12-1.41, P = 0.0001). CONCLUSION: In this cohort of patients with TG, glomerular C3 deposition was independently associated with a higher risk of allograft failure. These findings identify glomerular C3 as a novel prognostic indicator in patients with TG.

APRIL/BLyS Blockade Reduces Donor-specific Antibodies in Allosensitized Mice.

BACKGROUND: Highly sensitized candidates on the transplant waitlist remain a significant challenge, as current desensitization protocols have variable success rates of donor-specific antibody (DSA) reduction. Therefore, improved therapies are needed. A proliferation-inducing ligand (APRIL) and B-lymphocyte stimulator (BLyS) are critical survival factors for B-lymphocytes and plasma cells, which are the primary sources of alloantibody production. We examined the effect of APRIL/BLyS blockade on DSA in a murine kidney transplant model as a possible novel desensitization strategy. METHODS: C57BL/6 mice were sensitized with intraperitoneal (IP) injections of 2 × 10 BALB/c splenocytes. Twenty-one days following sensitization, animals were treated with 100 µg of BLyS blockade (B-cell activating factor receptor-immunoglobulin) or APRIL/BLyS blockade (transmembrane activator and calcium modulator and cyclophilin ligand interactor-immunoglobulin), administered thrice weekly for an additional 21 days. Animals were then euthanized or randomized to kidney transplant with Control Ig, BLyS blockade, or APRIL/BLyS blockade. Animals were euthanized 7 days posttransplant. B-lymphocytes and DSA of BLyS blockade only or APRIL/BLyS blockade-treated mice were assessed by flow cytometry, immunohistochemistry, and enzyme-linked immunospot. RESULTS: APRIL/BLyS inhibition resulted in a significant reduction of DSA by flow crossmatch compared with controls (P < 0.01). APRIL/BLyS blockade also significantly depleted IgM- and IgG-secreting cells and B-lymphocyte populations compared to controls (P < 0.0001). APRIL/BLyS blockade in transplanted mice also resulted in decreased B-lymphocyte populations; however, no difference in rejection rates were seen between groups. CONCLUSIONS: APRIL/BLyS blockade with transmembrane activator and calcium modulator and cyclophilin ligand interactor-immunoglobulin significantly depleted B-lymphocytes and reduced DSA in this sensitized murine model. APRIL/BLyS inhibition may be a clinically useful desensitization strategy for sensitized transplant candidates.

Desensitization and treatment with APRIL/BLyS blockade in rodent kidney transplant model.

Alloantibody represents a significant barrier in kidney transplant through the sensitization of patients prior to transplant through antibody mediated rejection (ABMR). APRIL BLyS are critical survival factors for mature B lymphocytes plasma cells, the primary source of alloantibody. We examined the effect of APRIL/BLyS blockade via TACI-Ig (Transmembrane activator calcium modulator cyclophilin lig interactor-Immunoglobulin) in a preclinical rodent model as treatment for both desensitization ABMR. Lewis rats were sensitized with Brown Norway (BN) blood for 21 days. Following sensitization, animals were then sacrificed or romized into kidney transplant (G4, sensitized transplant control); desensitization with TACI-Ig followed by kidney transplant (G5, sensitized + pre-transplant TACI-Ig); kidney transplant with post-transplant TACI-Ig for 21 days (G6, sensitized + post-transplant TACI-Ig); desensitization with TACI-Ig followed by kidney transplant post-transplant TACI-Ig for 21 days (G7, sensitized + pre- post-transplant TACI-Ig). Animals were sacrificed on day 21 post-transplant tissues were analyzed using flow cytometry, IHC, ELISPOT, RT-PCR. Sensitized animals treated with APRIL/BLyS blockade demonstrated a significant decrease in marginal zone non-switched B lymphocyte populations (p<0.01). Antibody secreting cells were also significantly reduced in the sensitized APRIL/BLyS blockade treated group. Post-transplant APRIL/BLyS blockade treated animals were found to have significantly less C4d deposition less ABMR as defined by Banff classification when compared to groups receiving APRIL/BLyS blockade before transplant or both before after transplant (p<0.0001). The finding of worse ABMR in groups receiving APRIL/BLyS blockade before both before after transplant may indicate that B lymphocyte depletion in this setting also resulted in regulatory lymphocyte depletion resulting in a worse rejection. Data presented here demonstrates that the targeting of APRIL BLyS can significantly deplete mature B lymphocytes, antibody secreting cells, effectively decrease ABMR when given post-transplant in a sensitized animal model.