Lois J. Arend

Treatment of C4D-positive acute humoral rejection with plasmapheresis and rabbit polyclonal antithymocyte globulin

Background. Alloantibody-mediated acute rejection is a major cause of renal allograft loss despite aggressive therapy. Patients with humoral rejection can be identified with high sensitivity and specificity by the presence of peritubular capillary C4d staining on renal biopsy and donor-specific anti-human leukocyte antigen antibodies. Standard therapy for acute humoral rejection (AHR) has been removal of donor-specific antibodies by plasmapheresis (PPH) in conjunction with intravenous immunoglobulin therapy. We describe a series of seven patients with C4d positive AHR who received combined therapy with PPH and polyclonal rabbit antithymocyte globulin (rATG). Methods. PPH (1.4 volume exchange) was initiated on diagnosis of AHR on an alternate day basis for a mean number of 6.8 treatments, in conjunction with rATG (0.75 mg/kg/day 5–10 days) until the serum creatinine returned to 120% of nadir. Results. The nadir posttreatment creatinine was significantly lower than pretreatment creatinine (1.0±1.2 vs. 2±1.4, P <0.007) with only one episode of graft loss. On follow-up there was no difference in renal allograft survival between the AHR group and the 60 patients without AHR who underwent transplantation during the same period. We describe the ability of rATG to induce apoptosis in vitro peripheral blood and activated B cells. Conclusion. Combination therapy using PPH and rATG is an effective means of reversing AHR in renal allografts.

Smac3, a Novel Smac/DIABLO Splicing Variant, Attenuates the Stability and Apoptosis-inhibiting Activity of X-linked Inhibitor of Apoptosis Protein

X-linked inhibitor of apoptosis protein (XIAP), the most potent member of the inhibitor of apoptosis protein (IAP) family, plays a crucial role in the regulation of apoptosis. XIAP is structurally characterized by three baculovirus IAP repeat (BIR) domains that mediate binding to and inhibition of caspases and a RING domain that confers ubiquitin ligase activity. The caspase inhibitory activity of XIAP can be eliminated by the second mitochondria-derived activator of caspases (Smac)/direct IAP-binding protein with low pI (DIABLO) during apoptosis. Here we report the identification and characterization of a novel isoform of Smac/DIABLO named Smac3, which is generated by alternative splicing of exon 4. Smac3 contains an NH2-terminal mitochondrial targeting sequence required for mitochondrial targeting of Smac3 and an IAP-binding motif essential for Smac3 binding to XIAP. Smac3 is released from mitochondria into the cytosol in response to apoptotic stimuli, where it interacts with the second and third BIR domains of XIAP. Smac3 disrupts processed caspase-9 binding to XIAP, promotes caspase-3 activation, and potentiates apoptosis. Strikingly, Smac3, but not Smac/DIABLO, accelerates XIAP auto-ubiquitination and destruction. Smac3-stimulated XIAP ubiquitination is contingent upon the physical association of XIAP with Smac3 and an intact RING domain of XIAP. Smac3-accelerated XIAP destabilization is, at least in part, attributed to its ability to enhance XIAP ubiquitination. Our study demonstrates that Smac3 is functionally additive to, but independent of, Smac/DIABLO.

Incidence and Outcomes of BK Virus Allograft Nephropathy among ABO- and HLA-Incompatible Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES ABO-incompatible kidney transplant recipients may have a higher incidence of BK virus allograft nephropathy (BKVAN) compared with ABO-compatible recipients. It is unclear whether HLA-incompatible recipients share this risk or whether this phenomenon is unique to ABO-incompatible recipients. DESIGN, SETTING, PARTICIPATION, MEASUREMENTS: This study analyzed adult incompatible kidney transplant recipients from 1998 to 2010 (62 ABO-incompatible and 221 HLA-incompatible) and identified patients in whom BKVAN was diagnosed by biopsy (per protocol or for cause). This was a retrospective analysis of a prospectively maintained database that compared BKVAN incidence and outcomes between ABO- and HLA-incompatible recipients, respectively. BKVAN link to rejection and graft accommodation phenotype were also explored. The Johns Hopkins Institutional Review Board approved this study. RESULTS Risk for BKVAN was greater among ABO-incompatible than HLA-incompatible patients (17.7% versus 5.9%; P=0.008). Of BKVAN cases, 42% were subclinical, diagnosed by protocol biopsy. ABO-incompatibility and age were independent predictors for BKVAN on logistic regression. C4d deposition without histologic features of glomerulitis and capillaritis (graft accommodation-like phenotype) on 1-year biopsies of ABO-incompatible patients with and without BKVAN was 40% and 75.8%, respectively (P=0.04). Death-censored graft survival (91%) and serum creatinine level among surviving kidneys (1.8 mg/dl) were identical in ABO- and HLA-incompatible patients with BKVAN (median, 1399 and 1017 days after transplantation, respectively). CONCLUSIONS ABO-incompatible kidney recipients are at greater risk for BKVAN than HLA-incompatible kidney recipients. ABO-incompatible recipients not showing the typical graft accommodation-like phenotype may be at heightened risk for BKVAN, but this observation requires replication among other groups.

Late antibody-mediated rejection in renal allografts: outcome after conventional and novel therapies.

Background Although several strategies for treating early antibody-mediated rejection (AMR) in kidney transplants have been investigated, evidence on treatment of late AMR manifesting after 6 months is sparse. In this single-center series, we present data on 23 consecutive patients treated for late AMR. Methods Late AMR was diagnosed using Banff 2007 criteria along with presence of donor-specific antibodies (DSA) and acute rise in serum creatinine (SCr). Response to therapy was assessed by improvement in SCr, histologic improvement, and decline in DSA strength. Results Overall, 17% (4/23) had documented nonadherence while 69% (16/23) had physician-recommended reduction in immunosuppression before AMR. Eighteen patients (78%) were treated with plasmapheresis or low-dose IVIg+rituximab; 11 (49%) with refractory AMR also received one to three cycles of bortezomib. While there was an improvement (P=0.02) in mean SCr (2.4 mg/dL) at the end of therapy compared with SCr at the time of diagnosis (2.9 mg/dL), this improvement was not sustained at most recent follow-up. Eleven (48%) patients had no histologic resolution on follow-up biopsy. Lack of histologic response was associated with older patients (odds ratio [OR]=3.17; P=0.04), presence of cytotoxic DSA at time of diagnosis (OR=200; P=0.04), and severe chronic vasculopathy (cv≥2) on index biopsy (OR=50; P=0.06). Conclusions A major setting in which late AMR occurred in our cohort was reduction or change in immunosuppression. Our data demonstrate an inadequate response of late AMR to current and novel (bortezomib) therapies. The benefits of therapy need to be counterweighed with potential adverse effects especially in older patients, large antibody loads, and chronic allograft vasculopathy.

Interstitial nephritis from mesalazine: case report and literature review.

We report a new case of biopsy-confirmed mesalazine-induced interstitial nephritis in an 18-year-old male with ulcerative colitis. His renal function improved with drug discontinuation and corticosteroid treatment. An English literature review revealed an additional 22 cases of this complication that, taken together, showed (1) a male predominance, (2) an absence of specific symptoms or findings on urinalysis, (3) a 61% frequency of residual chronic renal insufficiency with 13% of patients developing end-stage renal disease, and (4) an apparent favorable response to steroid therapy. We conclude that patients receiving 5-aminosalicylates should be routinely monitored with serum creatinine measurements to prevent this uncommon but potentially serious adverse drug reaction.

A renewable source of donor cells for repetitive monitoring of T- and B-cell alloreactivity

A major impediment to repetitive monitoring of alloreactivity or tolerance is the limited supply of donor cells available for assays of host‐versus‐graft T‐ and B‐cell reactivity. In this paper, we describe the use of CD40L stimulated CD19+ B cells as targets or stimulators in flow cytometric crossmatching (FXM), mixed lymphocyte reactivity and IFN‐γ ELISPOT assays. Stimulated B cells (sBc) express high levels of MHC class I and II, as well as the costimulatory molecules CD80 and CD86. They can be polyclonally expanded and frozen for later use. We describe the use of sBc in ELISPOT, mixed lymphocyte cultures and FXM. CD4+ T cells exposed to sBc express a similar cytokine profile as those stimulated with unfractionated PBMC. We further analyzed T‐ and B‐cell responses in 14 patients on the renal transplant waiting list, finding that those with an elevated panel reactive antibody (PRA) (>60%) had higher alloreactive T‐cell precursor frequencies as measured by CDFSE MLR and IFN‐γ ELISPOT. We conclude that sBc are a renewable source of donor‐specific target/stimulator cells for use in repetitive and coordinate assays of B‐ and T‐cell alloreactivity.

Dynamic regulation of sphingosine-1-phosphate homeostasis during development of mouse metanephric kidney

Branching morphogenesis of the metanephric kidney is critically dependent on the delicate orchestration of diverse cellular processes including proliferation, apoptosis, migration, and differentiation. Sphingosine-1-phosphate (S1P) is a potent lipid mediator influencing many of these cellular events. We report increased expression and activity of both sphingosine kinases and S1P phosphatases during development of the mouse metanephric kidney from induction at embryonic day 11.5 to maturity. Sphingosine kinase activity exceeded S1P phosphatase activity in embryonic kidneys, resulting in a net accumulation of S1P, while kinase and phosphatase activities were similar in adult tissue, resulting in reduced S1P content. Sphingosine kinase expression was greater in the metanephric mesenchyme than in the ureteric bud, while the S1P phosphatase SPP2 was expressed at greater levels in the ureteric bud. Treatment of cultured embryonic kidneys with sphingosine kinase inhibitors resulted in a dose-dependent reduction of ureteric bud tip numbers and increased apoptosis. Exogenous S1P rescued kidneys from apoptosis induced by kinase inhibitors. Ureteric bud tip number was unaffected by exogenous S1P in kidneys treated with N,N-dimethylsphingosine, although tip number increased in those treated with d,l-threo-dihydrosphingosine. S1P1 and S1P2 were the predominant S1P receptors expressed in the embryonic kidney. S1P1 expression increased during renal development while expression of S1P2 decreased, and both receptors were expressed predominantly in the metanephric mesenchyme. These results demonstrate dynamic regulation of S1P homeostasis during renal morphogenesis and suggest that differential expression of S1P metabolic enzymes and receptors provides a novel mechanism contributing to the regulation of kidney development.

Successful Renal Transplantation of Deceased Donor Kidneys With 100% Glomerular Fibrin Thrombi and Acute Renal Failure Due to Disseminated Intravascular Coagulation

Background Disseminated intravascular coagulation (DIC)-positive kidneys have historically been turned down for fear of poor outcomes. Higher severity injuries, which are prone to DIC, are typically seen in younger, otherwise healthy potential donors. The continued kidney allograft shortage has generated interest in the use of these DIC-positive grafts. There have been some reports of acceptable outcomes of renal transplantation using kidneys from donors with DIC. There are multiple clinical series demonstrating good outcomes from DIC-positive kidneys when the extent of glomeruli containing fibrin thrombi is less than 50% and donor renal function is preserved. These grafts are frequently associated with a period of delayed graft function. Methods We report 2 transplants with kidneys from brain dead donors with known DIC. Results Both donors had renal failure and pretransplant renal biopsies showing 100% of the glomeruli containing fibrin thrombi. The recipients experienced delayed graft function requiring hemodialysis which was discontinued on postoperative days 18 and 39 for cases 1 and 2, respectively. Both patients are now over 14 months posttransplant with stable allograft function. Conclusions Until clearer organ selection criteria are established, caution should be exercised when considering the use of kidneys with a similar phenotype and allocation decisions made by a multidisciplinary transplant team on a case-by-case basis.

Allograft Duodenal Cuff Biopsy as Surrogate in Evaluation of Pancreatic Transplant Rejection – A Multicenter Data Effort

Introduction Accurate diagnosis of pancreas rejection is required for early, targeted treatment and function preservation. Pancreas biopsy considered the gold standard presents with sampling issues and perceived procedural risks that limit its widespread use. Evaluation of the graft duodenal cuff, through upper endoscopy in intestine drained pancreas transplants has been proposed as a surrogate of pancreas biopsy but the utility of this approach has not been tested. In this multicenter effort we retrospectively evaluated pancreas and duodenal tissues collected simultaneously to correlate findings of acute cell-mediated rejection (ACR) in these two organs and offer interpretation of duodenal cuff biopsies as a potential diagnostic surrogate for its corresponding pancreas allograft. Materials and Methods A total of 88 cases were evaluated retrospectively from allograft pancreas performed between 1995 and 2015, with incidentally or intentionally obtained duodenal cuff mucosa from 11 reference tranplant centers in the North and South Americas, E.U. and U.K. These cases were re-analyzed and graded for ACR. Sixteen cases were excluded due to inadequate pancreas or duodenal sample, possible non-rejection biopsy findings or samples that were not simultaneously obtained. Of the remaining 72 cases, 50 were biopsies and 22 were explant cases. The cases were graded according to the Banff schema for grading pancreas allograft rejection (Drachenberg et al 2008) and from the schema for histologic grading of small intestine allografts (Wu et al 2008). Results Of the 72 cases, 20 cases showed a diagnosis of rejection. All 20 (100%) cases showed rejection in both pancreas and duodenal tissue. Fifty eight cases (80.5%) showed results that were concordant for a final diagnosis of rejection/suspicious for rejection or no evidence of rejection. Of the 14 (19.5%) cases that showed complete discordance (either suspected or diagnostic for rejection in pancreas but not duodenum or suspected or diagnostic for rejection in duodenum but not pancreas) 2 cases (2.7%) showed findings of rejection in the duodenum but not pancreas and 12 cases (16.6%) showed findings of rejection in pancreas but not in duodenum. Discussion In this cohort with simultaneous histological evaluation of pancreas parenchyma and graft duodenal cuff, a diagnosis of ACR in the duodenum showed a positive predictive value of 100% for pancreas ACR. Therefore evaluation of the duodenal cuff appears to be a useful surrogate in the absence of pancreas parenchyma in this setting. On the other hand, absence of rejection in the duodenum did not totally exclude rejecion in the pancreas, with a negative predictive value of 83%. Results that were graded as indeterminate (suspicious for) rejection in duodenum were not reliable and had both low PPV and NPV for pancreas rejection. Our results are encouraging and indicate the potential value of duodenal cuff evaluation, as well as the need for additional studies.

Granulomatous interstitial nephritis associated with bone marrow transplantation.

We describe two brothers with severe combined immunodeficiency, who presented with systemic granulomatous disease, with granulomatous interstitial nephritis as the main feature, several years following bone marrow transplantation. Neither brother had an apparent drug-induced, infectious disease or autoimmune source for the granulomatous interstitial nephritis. Both patients’ renal function improved following treatment with corticosteroids. This report implicates granulomatous interstitial nephritis as a complication of bone marrow transplantation for severe combined immunodeficiency.