Human autoimmune diseases thought to arise from the combined effects of multiple susceptibility genes include systemic lupus erythematosus (SLE) and autoimmune diabetes. Well-characterised polygenic mouse models closely resembling each of these diseases exist, and genetic evidence links receptors for the Fc portion of immunoglobulin G (FcR) with their pathogenesis in mice and humans [1] [2] [3]. FcRs may be activatory or inhibitory and regulate a variety of immune and inflammatory processes [4] [5]. FcgammaRII (CD32) negatively regulates activation of cells including B cells and macrophages [6]. FcgammaRII-deficient mice are prone to immune-mediated disease [7] [8] [9]. The gene encoding FcgammaRII, Fcgr2, is contained in genetic susceptibility intervals in mouse models of SLE such as the New Zealand Black (NZB) contribution to the (NZB x New Zealand White (NZW)) F1 strain [1] [10] [11] and the BXSB strain [12], and in human SLE [1] [2] [3]. We therefore sequenced Fcgr2 and identified a haplotype defined by deletions in the Fcgr2 promoter region that is present in major SLE-prone mouse strains (NZB, BXSB, SB/Le, MRL, 129 [13]) and non-obese diabetic (NOD) mice but absent in control strains (BALB/c, C57BL/6, DBA/2, C57BL/10) and NZW mice. The autoimmune haplotype was associated with reduced cell-surface expression of FcgammaRII on macrophages and activated B cells and with hyperactive macrophages resembling those of FcgammaRII-deficient mice, and is therefore likely to play an important role in the pathogenesis of SLE and possibly diabetes.
Maintenance immunosuppression with calcineurin inhibitors (CNIs) following renal transplantation is associated with nephrotoxicity and accelerated graft loss. We aimed to assess whether conversion to sirolimusbased immunosuppression would affect the progression of renal impairment.In this single center, randomized controlled trial, 40 renal transplant recipients between 6 months and 8 years post-transplant were randomly assigned to remain on their CNI (cyclosporin or tacrolimus) or to switch to sirolimus. The primary outcome measure was change in glomerular filtration rate (GFR) measurement at 12 months. Analysis was by intention-totreat.Of the 40 patients randomized, 2 patients never took the study drugs and were excluded, leaving 19 patients per group. There was a significant change in GFR at 12 months following conversion to sirolimus (12.9 mL/min, 95% CI 6.1-19.7; p < 0.001). Following conversion, the principal adverse events were the development of rashes (68%), particularly acne, and mouth ulcers (32%). No patient in either group experienced an acute rejection episode.In renal transplant recipients, a change in maintenance therapy from CNIs to sirolimus is associated with significant improvement in GFR at 12 months.
Background and objectives: Sevelamer carbonate is an improved, buffered form of sevelamer hydrochloride developed for the treatment of hyperphosphatemia in patients with chronic kidney disease. This study investigated the ability of sevelamer carbonate to control serum phosphorous in hyperphosphatemic patients who had chronic kidney disease and were not on dialysis.Design, setting, participants, & measurements:This was an open-label, dosage-titration study. Patients with serum phosphorus >5.5 mg/dl were enrolled (n ؍ 46). Sevelamer carbonate was administered for 8 wk. Patients were supplemented with native vitamin D (400 IU). The primary efficacy parameter was the change from baseline in serum phosphorous. Secondary measures included the percentage of serum phosphorus responders; changes in serum lipids, calcium-phosphorus product, and bicarbonate; and safety and tolerability.Results: Sevelamer carbonate treatment resulted in a statistically significant decrease in mean serum phosphorous levels from baseline to end of treatment. A total of 75% of patients with stage 4 and 70% of patients with stage 5 chronic kidney disease achieved the target serum phosphorous at the end of treatment. There were statistically significant decreases in serum calcium-phosphorus product and total and low-density lipoprotein cholesterol at the end of treatment and a statistically significant increase in mean serum bicarbonate levels (from 16.6 to 18.2 mEq/L). Sevelamer carbonate was well tolerated.Conclusions: Sevelamer carbonate is an effective and well-tolerated therapy for the control of phosphorous levels in hyperphosphatemic patients who have chronic kidney disease and are not on dialysis.
Inhibitory receptors CD22, FcγRII (CD32), CD72, and paired immunoglobulin-like receptor (PIR)-B are critically involved in negatively regulating the B cell immune response and in preventing autoimmunity. Here we show that interleukin 4 (IL-4) reduces expression of all four on activated B cells at the level of messenger RNA and protein. This reduced expression is dependent on continuous exposure to IL-4 and is mediated through Stat6. Coligation of FcγRII to the B cell receptor (BCR) via intact IgG increases the B cell activation threshold and suppresses antigen presentation. IL-4 completely abolishes these negative regulatory effects of FcγRII. CD22 coligation with the BCR also suppresses activation — this suppression too is abolished by IL-4. Thus, IL-4 is likely to enhance the B cell immune response by releasing B cells from inhibitory receptor suppression. By this coordinate reduction in expression of inhibitory receptors, and release from CD22 and FcγRII-mediated inhibition, IL-4 is likely to play a role in T cell help of B cells and the development of T helper cell type 2 responses. Conversely, B cell activation in the absence of IL-4 would be more difficult to achieve, contributing to the maintenance of B cell tolerance in the absence of T cell help.
Background and objectives The calcimimetic cinacalcet reduced the risk of death or cardiovascular (CV) events in older, but not younger, patients with moderate to severe secondary hyperparathyroidism (HPT) who were receiving hemodialysis. To determine whether the lower risk in younger patients might be due to lower baseline CV risk and more frequent use of cointerventions that reduce parathyroid hormone (kidney transplantation, parathyroidectomy, and commercial cinacalcet use), this study examined the effects of cinacalcet in older ($65 years, n=1005) and younger (,65 years, n=2878) patients.Design, setting, participants, & measurements Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) was a global, multicenter, randomized placebo-controlled trial in 3883 prevalent patients on hemodialysis, whose outcomes included death, major CV events, and development of severe unremitting HPT. The age subgroup analysis was prespecified.Results Older patients had higher baseline prevalence of diabetes mellitus and CV comorbidity. Annualized rates of kidney transplantation and parathyroidectomy were .3-fold higher in younger relative to older patients and were more frequent in patients randomized to placebo. In older patients, the adjusted relative hazard (95% confidence interval) for the primary composite (CV) end point (cinacalcet versus placebo) was 0.70 (0.60 to 0.81); in younger patients, the relative hazard was 0.97 (0.86 to 1.09). Corresponding adjusted relative hazards for mortality were 0.68 (0.51 to 0.81) and 0.99 (0.86 to 1.13). Reduction in the risk of severe unremitting HPT was similar in both groups. ConclusionsIn the EVOLVE trial, cinacalcet decreased the risk of death and of major CV events in older, but not younger, patients with moderate to severe HPT who were receiving hemodialysis. Effect modification by age may be partly explained by differences in underlying CV risk and differential application of cointerventions that reduce parathyroid hormone.
We have previously reported the pattern of cellular expression of tumor necrosis factor receptors (TNFR) in human kidney and their altered expression in transplant rejection. We have extended our studies to examine the expression of Silencer of Death Domains (SODD), a protein that binds to the cytoplasmic portion of TNFR1 to inhibit signaling in the absence of ligand. In normal human kidney SODD is expressed in glomerular endothelial cells where it colocalizes with TNFR1. During acute rejection both SODD and TNFR1 are lost from glomeruli, but we found strong expression of SODD on the luminal surface of tubular epithelial cells. This occurs in the absence of detectable TNFR1 expression, suggesting that SODD could interact with other proteins at these sites. Several other members of the TNF superfamily, including Fas and death receptors (DR)-3, -4, and -5, also contain intracellular death domains, but SODD only interacts with the death domain of DR3. We therefore studied the expression of DR3 in human kidney, and report that this death receptor is up-regulated in renal tubular epithelial cells and endothelial cells of some interlobular arteries, in parallel with SODD, during acute transplant rejection. In less severe rejection episodes, DR3 and SODD were more focally induced, generally at sites of mononuclear cell infiltrates. In ischemic allografts, eg, with acute tubular necrosis but no cellular rejection, DR3 was induced on tubular epithelial cells and on glomerular endothelial cells. These data confirm that TNF receptor family members are expressed in a regulated manner during renal transplant rejection, and identify DR3 as a potential inducible mediator of tubular inflammation and injury.
Donor-specific HLA alloantibodies may cause acute and chronic antibody-mediated rejection (AMR) and significantly compromise allograft survival. The clinical relevance of antibodies directed against some HLA class II antigens, particularly HLA-DP, is less clear with conflicting reports on their pathogenicity. We report two patients with high levels of pretransplant donorspecific HLA-DP antibodies who subsequently developed recurrent acute AMR and graft failure. In both cases, there were no other donor-specific HLA alloantibodies, suggesting that the HLA-DP-specific antibodies may be directly pathogenic.
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