Effect of Replacing Race With Apolipoprotein L1 Genotype in Calculation of Kidney Donor Risk Index.

Renal allografts from deceased African American donors with two apolipoprotein L1 gene (APOL1) renal-risk variants fail sooner than kidneys from donors with fewer variants. The Kidney Donor Risk Index (KDRI) was developed to evaluate organ offers by predicting allograft longevity and includes African American race as a risk factor. Substituting APOL1 genotype for race may refine the KDRI. For 622 deceased African American kidney donors, we applied a 10-fold cross-validation approach to estimate contribution of APOL1 variants to a revised KDRI. Cross-validation was repeated 10 000 times to generate distribution of effect size associated with APOL1 genotype. Average effect size was used to derive the revised KDRI weighting. Mean current-KDRI score for all donors was 1.4930 versus mean revised-KDRI score 1.2518 for 529 donors with no or one variant and 1.8527 for 93 donors with two variants. Original and revised KDRIs had comparable survival prediction errors after transplantation, but the spread in Kidney Donor Profile Index based on presence or absence of two APOL1 variants was 37 percentage points. Replacing donor race with APOL1 genotype in KDRI better defines risk associated with kidneys transplanted from deceased African American donors, substantially improves KDRI score for 85-90% of kidneys offered, and enhances the link between donor quality and recipient need.

Apolipoprotein L1 gene variants in deceased organ donors are associated with renal allograft failure.

Apolipoprotein L1 gene (APOL1) nephropathy variants in African American deceased kidney donors were associated with shorter renal allograft survival in a prior single-center report. APOL1 G1 and G2 variants were genotyped in newly accrued DNA samples from African American deceased donors of kidneys recovered and/or transplanted in Alabama and North Carolina. APOL1 genotypes and allograft outcomes in subsequent transplants from 55 U.S. centers were linked, adjusting for age, sex and race/ethnicity of recipients, HLA match, cold ischemia time, panel reactive antibody levels, and donor type. For 221 transplantations from kidneys recovered in Alabama, there was a statistical trend toward shorter allograft survival in recipients of two-APOL1-nephropathy-variant kidneys (hazard ratio [HR] 2.71; p = 0.06). For all 675 kidneys transplanted from donors at both centers, APOL1 genotype (HR 2.26; p = 0.001) and African American recipient race/ethnicity (HR 1.60; p = 0.03) were associated with allograft failure. Kidneys from African American deceased donors with two APOL1 nephropathy variants reproducibly associate with higher risk for allograft failure after transplantation. These findings warrant consideration of rapidly genotyping deceased African American kidney donors for APOL1 risk variants at organ recovery and incorporation of results into allocation and informed-consent processes.

Familial IgA nephropathy in southeastern Kentucky.

BACKGROUND: Two decades ago, pedigrees of patients with IgA nephropathy (IgAN) from Pike County, KY, USA, provided evidence for a role of genetic factors in the pathogenesis of this disorder. Subsequently additional pedigrees were described for several communities from northern Italy. Recently, we found another cluster of patients in the Clay County, KY area, about 100 miles southwest of Pike County. AIM: The purpose of this study was to evaluate and expand the pedigrees of patients with IgAN from Clay County, KY to provide additional insight into the mechanisms of inheritance of IgAN and assess the possible influence of a founder effect on the prevalence of IgAN in the region. METHOD: Since 1980, most patients with IgAN and their relatives in eastern KY have provided personal genealogic data. These data were used to construct pedigrees that included the patients born in Clay County. Nine of 11 patients with IgAN born in Clay County, KY, USA were members of 1 or more of 5 pedigrees, each with 3 - 11 patients with IgAN. CONCLUSION: Our findings suggest the possibility of a low-penetrance ancestral mutation in the IgAN kindreds from Clay County.

Secondary listing for deceased-donor kidney transplantation does not increase likelihood of engraftment at a large transplant center.

The supply of donor organs has not increased as fast as has the number of patients awaiting kidney transplantation. Few organs are shared outside the areas of recovery. This trend has caused some ESRD patients to seek listing at multiple centers. We examined UNOS registry data and transplant registry data at the University of Alabama at Birmingham (UAB) for the 576 patients listed at multiple centers over an 8-year span ending December 31, 2005. We identified 72 multilisted patients who received a deceased-donor renal allograft at UAB and reviewed their records for demographics, HLA matching and transfer of listing time. The only predictors for transplantation at UAB were initial listing at UAB or transfer of waiting time. Fifty-one of the 72 patients had listed at UAB first; the other 21 had transferred waiting time. None of the 176 patients who listed elsewhere first and did not transfer waiting time had been transplanted at UAB. Aggregate cost of listing and evaluation for the 176 patients listed elsewhere first who did not transfer waiting time was $1 254 528. Secondary listing at UAB, with a large cohort awaiting transplantation, without transfer of waiting time from another center was an expensive and futile process.

Isolated central nervous system posttransplant lymphoproliferative disorder treated with high-dose intravenous methotrexate.

Posttransplant lymphoproliferative disorder (PTLD) is an uncommon neoplastic complication of kidney transplantation, affecting about 1% of recipients. It is generally associated with Epstein-Barr virus (EBV) infection of B-lineage lymphocytes. Central nervous system (CNS) involvement is rare. There is little clinical experience with treatment of CNS PTLD due to the relative rarity of the disease other than reduction or withdrawal of immunosuppression, but it is usually fatal. We describe six patients with renal allografts and histologically proven isolated CNS PTLD. Tissue analysis from the biopsy specimens was positive for EBV material in five of the six patients. All six patients were treated with high-dose intravenous methotrexate (HD IV MTX). Methotrexate was initiated at 8 g/m2, with later adjustments for creatinine clearance. With MTX therapy, four patients have had a sustained complete response, and two had progressive disease and were referred for radiation therapy. This finding suggests a subgroup of patients may benefit from MTX but our case series is inadequate to describe overall efficacy. No unexpected toxicities were encountered in 37 courses of treatment. HD IV MTX chemotherapy should be considered as an alternative for treatment of CNS PTLD.

Role of aberrant glycosylation of IgA1 molecules in the pathogenesis of IgA nephropathy.

Studies of the properties of immune complexes (IC) in the circulation, urine, and mesangium of IgA nephropathy (IgAN) patients have provided data relevant to the pathogenesis of this disease. IC contain predominantly polymeric IgA1 molecules which are deficient in galactose (Gal) residues on O-linked glycan chains in the hinge region (HR) of their heavy (H) chains. As a result of this aberrancy, a novel antigenic determinant(s) involving N-acetylgalactosamine (GalNAc) and perhaps sialic acid (SA) of O-linked glycans is generated and recognized by naturally occurring GalNAc-specific antibodies. Thus, IC in IgAN consist of Gal-deficient IgA1 molecules as an antigen, and GalNAc-specific IgG and/or IgA1 as an antibody. IgG antibodies to Gal-deficient IgA1 are probably induced by cross-reactive microbial antigens; they are present at variable levels not only in humans with or without IgAN but also in many phylogenetically diverse vertebrate species. Incubation of human mesangial cells with IC from sera of IgAN patients indicated that stimulation of cellular proliferative activity was restricted to the large (>800 kDa) complexes. These findings suggest that experimental approaches that prevent the formation of large Gal-deficient IgA1-IgG IC may be applied ultimately in an immunologically mediated therapy.

Patients with IgA nephropathy have increased serum galactose-deficient IgA1 levels.

Immunoglobulin A (IgA) nephropathy is the most prevalent form of glomerulonephritis worldwide. A renal biopsy is required for an accurate diagnosis, as no convenient biomarker is currently available. We developed a serological test based upon the observation that this nephropathy is characterized by undergalactosylated IgA1 in the circulation and in mesangial immune deposits. In the absence of galactose, the terminal saccharide of O-linked chains in the hinge region of IgA1 is terminal or sialylated N-acetylgalactosamine. A lectin from Helix aspersa, recognizing N-acetylgalactosamine, was used to develop an enzyme-linked immunosorbent assay that measures galactose-deficient IgA1 in serum. The median serum lectin-binding IgA1 level was significantly higher for 153 Caucasian adult patients with IgA nephropathy without progression to end-stage renal disease as compared with that for 150 healthy Caucasian adult controls. As the lectin-binding IgA1 levels for the controls were not normally distributed, the 90th percentile was used for determination of significant elevation. Using a value of 1076 U/ml as the upper limit of normal, 117 of the 153 patients with IgA nephropathy had an elevated serum lectin-binding IgA1 level. The sensitivity as a diagnostic test was 76.5%, with specificity 94%; the positive predictive value was 88.6% and the negative predictive value was 78.9%. We conclude that this lectin-binding assay may have potential as a noninvasive diagnostic test for IgA nephropathy.

Incidence of hip osteonecrosis among renal transplantation recipients: a prospective study.

AIM: To investigate whether a lessened glucocorticoid cumulative dose would lead to a decreased incidence of femoral head osteonecrosis. METHODS: Newly transplanted in-patients (n = 49) underwent hip radiographs and magnetic resonance imaging (MRI) a mean of 17.0+/-4.3 (range 8-29) days after renal transplantation. For the 48 patients without evidence of prevalent osteonecrosis, imaging at a mean of 5.9+/-0.8 (range 4.8-8.7) months after renal transplantation was graded for presence/absence of femoral head osteonecrosis by two blinded radiologists. Sociodemographic and disease characteristics of patients were compared to identify potential associations with incident osteonecrosis. RESULTS: At 6-month follow-up, only two patients (4%) had osteonecrosis of the femoral head (three hips). The two primary radiologists had excellent agreement between osteonecrosis diagnosis (kappa coefficient=0.78). Both cases of a definite MRI diagnosis of osteonecrosis occurred in patients who were in the highest tertile of glucocorticoid dosage. CONCLUSION: Osteonecrosis was uncommon among a prospective cohort of renal transplant recipients within 6 months after engraftment.

Progress in molecular and genetic studies of IgA nephropathy.

Several new findings emerged recently from biochemical, genetic, and molecular studies of patients with IgA nephropathy. It appears that immunoglobulin A1-secreting cells of IgA nephropathy patients produce increased amounts of aberrantly glycosylated IgA1 in which the O-linked glycans in the hinge region are deficient in the content of galactose. The galactose-deficient IgA1 in the circulation is recognized by naturally occurring antibodies with anti-glycan specificity, and immune complexes are formed. These circulating immune complexes escape hepatic degradation and eventually are deposited in the kidney mesangium. Resident mesangial cells bind the IgA-containing immune complexes with the involvement of a novel IgA receptor and become activated. A familial form of IgA nephropathy has been linked to chromosome 6q22-23. Recent progress in molecular analyses of IgA nephropathy thus defines this disease as an autoimmune process with a novel IgA mesangial receptor and certain genetically determined traits.

Tolerance in renal transplantation after allogeneic bone marrow transplantation-6-year follow-up.

Despite significant advancements in clinical transplantation, very few reports describe the long-term acceptance of transplanted solid organs without indefinite immunosuppression. The immunosuppressive agents used are nonspecific and have serious potential side effects. We present a patient who received a living-donor renal allograft from the same person who had donated bone marrow to her several years earlier. Tolerance was expected based on previous acceptance of full-thickness skin grafts from the donor. Indeed, there has been no evidence of rejection during a 6-year follow-up period, and no induction or maintenance immunosuppression has been given. All noninvasive parameters of graft function remain normal. This and similar reports prove that genetically disparate solid organs can coexist without pharmacological immunosuppression.

IgA nephropathy, the most common cause of glomerulonephritis, is linked to 6q22-23.

End-stage renal disease (ESRD) is a major public health problem, affecting 1 in 1,000 individuals and with an annual death rate of 20% despite dialysis treatment. IgA nephropathy (IgAN) is the most common form of glomerulonephritis, a principal cause of ESRD worldwide; it affects up to 1.3% of the population and its pathogenesis is unknown. Kidneys of people with IgAN show deposits of IgA-containing immune complexes with proliferation of the glomerular mesangium (Fig. 1). Typical clinical features include onset before age 40 with haematuria and proteinuria (blood and protein in the urine), and episodes of gross haematuria following mucosal infections are common; 30% of patients develop progressive renal failure. Although not generally considered a hereditary disease, striking ethnic variation in prevalence and familial clustering, along with subclinical renal abnormalities among relatives of IgAN cases, have suggested a heretofore undefined genetic component. By genome-wide analysis of linkage in 30 multiplex IgAN kindreds, we demonstrate linkage of IgAN to 6q22-23 under a dominant model of transmission with incomplete penetrance, with a lod score of 5.6 and 60% of kindreds linked. These findings for the first time indicate the existence of a locus with large effect on development of IgAN and identify the chromosomal location of this disease gene.

Focal posttransplantation lymphoproliferative disorder at the renal allograft hilum.

OBJECTIVE: This report describes the imaging characteristics of focal posttransplantation lymphoproliferative disorder. CONCLUSION: Posttransplantation lymphoproliferative disorder may be limited to the allograft. A focal complex mass in the renal allograft hilum surrounding the main renal blood vessels is a common finding and can be visualized with sonography. MR imaging can help increase diagnostic confidence.

Treatment of IgA nephropathy.

IgA nephropathy (Berger's disease) is the most common primary glomerulonephritis worldwide and was once equated with benign recurrent hematuria. Longer observation showed that 15% to 30% of patients progress to end-stage renal failure after 20 years of clinical manifestations. Because the pathogenesis remains enigmatic, therapy to ameliorate disease progression can not be disease-specific. Several approaches to treatment have generated increasing interest in the last few years, including angiotensin inhibition, glucocorticoids, fish oil, cyclophosphamide, tonsillectomy and mycophenolate mofetil. For patients reaching end-stage renal failure, recurrent disease after transplantation remains a clinically important problem, despite immunosuppression since engraftment.

Postransplant lymphoproliferative disorder localized near the allograft in renal transplantation.

BACKGROUND: Posttransplant lymphoproliferative disorder (PTLD), a complication of immunosuppression, develops in approximately 1% of renal allograft recipients. Typically, PTLD is a proliferation of B-cells associated with Epstein-Barr virus (EBV) infection; it is said to be most often a systemic disease. Involvement occasionally is localized near the allograft. METHODS: This is a retrospective analysis of all cases of PTLD in recipients of 1474 renal transplants performed at University of Alabama at Birmingham between 1993 and 1997. RESULTS: Of 14 patients developing PTLD, 10 had disease localized near the allograft. The mean interval from transplantation to diagnosis was 221 +/- 70 days. All patients presented with renal dysfunction; an ultrasound examination revealed a hilar mass, with hydronephrosis in five and stenosis of renal vessels in eight. No patient had lymphadenopathy, according to computerized tomographic or magnetic resonance imaging findings. After reduction of immunosuppressive therapy, seven required a nephrectomy because of rejection, progressive dysfunction, or mass enlargement. Tissue recovered in four patients was consistent with PTLD; the tumors in the remaining three patients were unresectable and regressed. One patient died 1 month after a nephrectomy, and another died 4 years after surgery; neither had evidence of PTLD when they died. Three patients retain functional grafts without clinical or radiographical evidence of progression. All patients with disseminated disease died. CONCLUSIONS: In a large cohort of renal allograft recipients, PTLD affected 1%. Disease localized near the allograft was the most common variant. For most patients with localized disease, the outcome was graft loss, and the mortality was low. Localized PTLD should be considered in the differential diagnosis of allograft dysfunction in the 1st posttransplant year.

Sirolimus reduces the incidence of acute rejection episodes despite lower cyclosporine doses in caucasian recipients of mismatched primary renal allografts: a phase II trial. Rapamune Study Group.

BACKGROUND: The novel agent sirolimus (SRL; Rapamune; rapamycin) inhibits the immune response by a mechanism distinct from those of calcineurin antagonists or antimetabolites. This randomized, controlled, multicenter, single blind, phase II trial examined the combination of SRL, steroids, and full versus reduced doses of cyclosporine (CsA) for prophylaxis of acute renal allograft rejection. METHODS: A total of 149 recipients of mismatched cadaveric- or living-donor primary renal allografts were randomized into six groups. Three groups received placebo or 1 or 3 mg/m2/day SRL, as well as steroids and full-dose CsA (Sandimmune). Three groups received steroids, reduced-dose CsA (target trough level 50% of full-dose range), and 1, 3, or 5 mg/m2/day SRL. RESULTS: The incidence of biopsy-proven acute rejection episodes within the first 6 months after transplant was reduced from 32.0% in the control group to 8.5% in patients receiving SRL (1 or 3 mg/m2/day) and full-dose Sandimmune CsA (P=0.018). Similar low rates of acute rejection episodes were observed among non-African-Americans, but not African-Americans, treated with SRL and reduced-dose Sandimmune CsA. Despite the augmented immunosuppression, 1-year patient and graft survival rates did not differ significantly across groups. Adverse effects attributable to CsA, including hypertension and new-onset diabetes mellitus, were not exacerbated by SRL. Except for an increased incidence of pneumonia among patients receiving full-dose CsA and 3 mg/m2/day SRL, the incidences of opportunistic infections were similar in all treatment groups. Although SRL produced more frequent, but reversible, hematological and lipid abnormalities, it had no apparent nephrotoxic effects to exacerbate CsA-induced renal dysfunction. CONCLUSIONS: SRL in combination with CsA and steroids not only lowers the incidence of biopsy-proven acute renal allograft rejection episodes, but also may permit CsA sparing, at least among Caucasian patients, without an increased risk of rejection.

Progress in the pathogenesis of IgA nephropathy.

Despite 31 years of clinical and laboratory investigation, the pathogenesis of IgAN remains largely enigmatic. However, it seems clear that IgA1 accumulates in the glomerular mesangia due to a systemic process rather than an abnormality intrinsic in the kidney. Based on recent studies, investigators have proposed a wide range of pathogenetic mechanisms: nonspecific attachment because excessive IgA1 is synthesized in a short or prolonged immune response, increased binding due to an IgA-specific receptor (perhaps with altered characteristics) on mesangial cells, and increased glomerular deposition because an abnormal structure of the antibody (particularly of the glycan moieties in the hinge region) allows it to escape its normal degradative pathways or facilitates binding to a receptor on mesangial cells. Whether one or more of these postulates fully explains IgAN remains to be determined. Until then, treatment of the many affected patients worldwide will continue to lack a disease-specific approach.

Expression of stem cell factor by osteoblasts in normal and hyperparathyroid bone: relation to ectopic mast cell differentiation.

Mast cells accumulate in hyperparathyroid bone, but the reason is not clear. We compared the distribution of mast cells and related growth factors in normal and hyperparathyroid bone. Mast cell formation was strongly affected by proximity to bone-forming surfaces of hyperparathyroid bone. Hyperparathyroidism greatly increased the production by active, bone-synthesizing osteoblasts of stem cell factor (SCF) but not of IL-3. Osteoblast SCF was distributed to the basolateral cell membranes, and its cDNA sequence (GenBank AF119835) is homologous to the murine membrane-bound SCF. Quiescent osteoblasts did not produce detectable SCF. Synthetic osteoblasts in normal bone were SCF positive, but comprised a much smaller population of cells, in keeping with the slow turnover of normal bone. Major SCF isoforms on immunoblot analysis of osteoblast-fraction proteins from high-turnover bone had M(r)s of about 48 and 40 kDa. Similar SCF isoforms were produced by MG63 osteoblast-derived cells and were identified by several anti-SCF antibodies. SCF is expressed in several mesenchymal cell types in a complementary fashion with cells bearing its receptor. SCF potently facilitates differentiation of mast cells, so the increase in paratrabecular mast cells in hyperparathyroid bone is probably driven by osteoblastic SCF. However, since mast cells are not normal components of bone, osteoblastic SCF probably regulates other cells, with mast cell differentiation occurring as a side effect greatly increased osteoblastic activity.

Treatment of immunoglobulin A nephropathy.

In this review, therapeutic trials for treatment of IgA nephropathy (Berger's disease) are reviewed and discussed. No disease-specific therapy exists. For treatment of hypertensive patients, angiotensin converting enzyme (ACE) inhibitors are preferred. They also decrease proteinuria and probably slow disease progression. However, there are still no controlled data on the effectiveness of ACE-inhibitors in the absence of hypertension or proteinuria. Renewed enthusiasm for treatment with fish oil arose after the publication of a randomized controlled trial in 1994 and long-term follow-up data of the trial cohort in 1998. Corticoid therapy in IgA nephropathy has been advocated for patients with nephrotic syndrome or crescentic disease. A recent non-randomised trial with long-term follow-up suggests that, in the presence of moderate proteinuria, corticosteroids may ameliorate renal function if administered before the creatinine clearance has decreased below 70 ml/min. Preliminary data suggest that mycophenolate mofetil (MMF) may reduce the risk of clinically significant IgA nephropathy recurring in kidney allografts. Many other promising treatment approaches have been tested, but in most instances results are insufficient for unequivocal conclusions. Several randomized controlled clinical trials are currently testing prednisone, fish oil, ACE-inhibitors, cyclophosphamide, MMF and vitamin E. In the absence of a disease-specific treatment, control of hypertension, proteinuria and probably dyslipidemia are pivotal. Chronic or recurrent infection including ton-sillitis should be treated effectively. Control of daily protein intake to 0.7-0.8 g/kg body weight may retard disease progression.

Circulating immune complexes in IgA nephropathy consist of IgA1 with galactose-deficient hinge region and antiglycan antibodies.

Circulating immune complexes (CICs) isolated from sera of patients with IgA nephropathy (IgAN) consist of undergalactosylated, mostly polymeric, and J chain-containing IgA1 and IgG antibodies specific for N-acetylgalactosamine (GalNAc) residues in O-linked glycans of the hinge region of IgA1 heavy chains. Antibodies with such specificity occur in sera of IgAN patients, and in smaller quantities in patients with non-IgA proliferative glomerulonephritis and in healthy controls; they are present mainly in the IgG (predominantly IgG2 subclass), and less frequently in the IgA1 isotype. Their specificity for GalNAc was determined by reactivity with IgA1 myeloma proteins with enzymatically removed N-acetylneuraminic acid (NeuNAc) and galactose (Gal); removal of the O-linked glycans of IgA1 resulted in significantly decreased reactivity. Furthermore, IgA2 proteins that lack the hinge region with O-linked glycans but are otherwise structurally similar to IgA1 did not react with IgG or IgA1 antibodies. The re-formation of isolated and acid-dissociated CICs was inhibited more effectively by IgA1 lacking NeuNAc and Gal than by intact IgA1. Immobilized GalNAc and asialo-ovine submaxillary mucin (rich in O-linked glycans) were also effective inhibitors. Our results suggest that the deficiency of Gal in the hinge region of IgA1 molecules results in the generation of antigenic determinants containing GalNAc residues that are recognized by naturally occurring IgG and IgA1 antibodies.

Parathyroid hormone-regulated production of stem cell factor in human osteoblasts and osteoblast-like cells.

We investigated stem cell factor (SCF) expression in osteoblasts because mast cells, which occur ectopically in hyperparathyroid bone, are induced by SCF. Nontransformed osteoblasts and Saos2 or MG63 cells expressed SCF in response to PTH. Western analysis showed only large, cell-associated isoforms, Mrs approximately 40-48 kD. Transfection of MG63 cells with plasmids expressing antisense SCF mRNA eliminated immunoreactive SCF. Sequencing osteoblast SCF cDNAs showed that exon 6 was omitted. mRNAs without exon 6 produce membrane-associated SCF isoforms in rodents, suggesting that human SCFs are processed similarly. The major osteoblastic SCF mRNA, approximately 5 kB, was augmented by PTH. Neither protein or mRNA was increased by vitamin D, however, 6-7 kB transcripts were predominant in other tissues but not detectable in osteoblasts. We conclude that osteoblasts express SCF in response to PTH, with mRNA and protein processing differences relative to other cells. SCF stimulates osteoclasts, suggesting that PTH-induced osteoblastic SCF functions to accelerate bone turnover. Mast cells may occur due to SCF overexpression at extreme PTH levels.