Dynamics of HLA and angiotensin II type 1 receptor antibodies during pregnancy.

BACKGROUND: Alloantibodies, especially anti-human leukocyte antigen antibodies (HLA antibodies), and autoantibodies, as angiotensin II type 1 receptor antibodies (AT1R antibodies), may complicate the access and the course of transplantation. Pregnancy is a known source of HLA antibodies, with most studies evaluating pregnancy-induced sensitization by complement-dependent cytotoxicity assays, mainly after childbirth. AT1R antibodies have been evaluated in the context of preeclampsia. We aimed to evaluate pregnancy as a natural source of HLA antibodies and AT1R antibodies, their dynamics along gestation and the potential factors involved in antibody appearance. METHODS: Serum samples from pregnant women were collected during the three trimesters of pregnancy (1T, 2T, 3T). Presence of HLA antibodies was assessed by screening beads on Luminex and AT1R antibodies by ELISA. RESULTS: A cohort of 138 pregnant women were included. Samples from all were tested in 1T, 127 in 2T and 102 in 3T. HLA antibodies increased from 29.7 % (1T) to 38.2 % (3T). AT1R antibodies were stable around 30 % along pregnancy. Up to 43.2 % multiparous women had HLA antibodies, with a similar proportion of class I and class II antibodies. In primiparous women HLA antibodies increased along pregnancy (from 17.6 % to 34.1 %), with predominance of class II HLA antibodies. AT1R antibodies were not different in primiparous and multiparous women. CONCLUSIONS: Pregnancy is a relevant source of HLA antibodies sensitization, but not of AT1R antibodies. HLA antibodies increased clearly in primiparous women with predominance of class II. The use of newer solid-phase techniques on Luminex evidence a higher degree of HLA sensitization during pregnancy.

Phosphorylation of S6RP in peritubular capillaries of kidney grafts and circulating HLA donor-specific antibodies.

Antibody-mediated rejection (ABMR) caused by donor-specific HLA-antibodies (DSA) is a mediator of allograft loss after kidney transplantation (KT). DSA can activate microvascular endothelium damage through the mTOR pathway. In this study we assessed the mTOR pathway activation by DSA in KT with ABMR (ABMR + DSA+) compared to controls (ABMR-DSA-), biopsies with ABMR changes without DSA (ABMR + DSA-) and DSA without ABMR changes (ABMR-DSA+), and the potential modulation by mTOR inhibitors (mTORi). We evaluated 97 biopsies: 31 ABMR + DSA+, 33 controls ABMR-DSA-, 16 ABMR + DSA-, and 17 ABMR-DSA+ cases. Regarding immunosuppression of full ABMR + DSA+ and controls, 21 biopsies were performed under mTORi treatment (11 of them ABMR + DSA+ cases) and 43 without mTORi (20 of them ABMR + DSA+) so as to explore its effect on the mTOR pathway. Biopsies were stained for C4d, Ki67, and phosphorylated (p) S6RP, ERK, and mTOR by immunohistochemistry. Labeling was graded according to peritubular capillary staining. ABMR biopsies showed significantly higher C4d, p-S6RP, and Ki67 staining in peritubular capillaries (PTC) compared to controls, and light differences in p-ERK or p-mTOR. mTORi treatment did not modify p-S6RP, p-mTOR, and p-ERK staining. Diffuse p-S6RP in PTC in the biopsies significantly associated with circulating HLA-DSA independently of graft rejection, and with worse death-censored graft survival. These findings suggest that activation of endothelium through the mTOR pathway evidence different mechanisms of damage in ABMR + DSA+ and ABMR + DSA- despite similar histological injury.

[Cinacalcet in the management of normocalcaemic secondary hyperparathyroidism after kidney transplantation: one-year follow-up multicentre study]. / Cinacalcet en el manejo del hiperparatiroidismo secundario normocalcémico tras el trasplante renal: estudio multicéntrico de un año de seguimiento.

BACKGROUND: The effect of cinacalcet in patients with persistent secondary hyperparathyroidism (SHPT) after kidney transplantation (RT) has mainly been reported in patients with secondary hypercalcaemia. OBJECTIVES: Our objective was to assess the long-term effect of cinacalcet on patients with a RT and normocalcaemic SHPT. METHODS: A one-year multicentre, observational, retrospective study that included kidney recipients with SHPT (intact parathyroid hormone [iPTH] >120 pg/ml) and calcium levels within the normal range (8.4-10.2 mg/dl). Patients began treatment with cinacalcet in clinical practice. RESULTS: 32 patients with a mean age (standard deviation [SD]) of 54 (11) years, 56% male, were included in the study. Treatment with cinacalcet began a median of 16 months after RT (median dose of 30 mg/day). Levels of iPTH decreased from a median (P25, P75) of 364 (220, 531) pg/ml at the start of the study to 187 (98, 320) after 6 months (48.6% reduction, P=.001) and to 145 (91, 195) after 12 months (60.2% reduction, P=.001), without there being changes in calcium and phosphorus levels (P=.214 and P=.216, respectively). No changes were observed in kidney function or anti-calcineuric drug levels. 3.1% of patients discontinued cinacalcet due to intolerance and 6.2% due to a lack of efficacy. CONCLUSIONS: In patients with normocalcaemic SHPT after RT, cinacalcet improves the control of serum PTH values without causing changes to calcaemia, phosphataemia or kidney function. Cinacalcet showed good tolerability.

C4d as a diagnostic tool in membranous nephropathy.

INTRODUCTION: membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults. The diagnosis is based on typical findings observed using electron microscope (EM) and immunofluorescence (IF) studies. On some occasions, tissues are only available for analysis using an optical microscope (OM); in these cases, it can be difficult to differentiate between MN and minimal change disease (MCD). Recently, the use of C4d immunohistochemical staining has spread. Very little information is available regarding C4d deposits in MN. Our study consisted of analysing whether C4d staining of samples embedded in paraffin could be useful for diagnosing MN. MATERIAL AND METHOD: Ours was a retrospective study including all patients diagnosed with MN by renal biopsy in our unit between January 2001 and October 2008. We only included adult patients with a definitive diagnosis of MN or idiopathic MCD by OM, IF, and ME studies. In October 2008, 3µm sections of renal tissue fixed in formaldehyde were removed from paraffin and rehydrated. The samples were then stained for C4d immunohistochemical analysis using anti-human polyclonal antibodies obtained from rabbits. RESULTS: Our study included a final sample of 19 patients with MCD and 21 with MN. No C4d deposits were observed in any of the glomeruli in patients with MCD, and 100% of these patients were classified as negative. However, C4d deposits were detected in 100% of patients with MN, and were observable in all glomeruli with a uniform granular distribution, demarcating all capillary loops. CONCLUSIONS: C4d immunohistochemical staining is a very useful tool for diagnosing MN.

C4d como herramienta diagnóstica en la nefropatía membranosa / C4d as a diagnostic tool in membranous nephropathy

Introducción: La nefropatía membranosa (NM) es la causa más frecuente de síndrome nefrótico en adultos. El diagnóstico se basa en los hallazgos típicos observados con el microscopio electrónico (ME) y el estudio de inmunofluorescencia (IF). En algunas ocasiones, sólo se dispone de tejido para estudio de microscopio óptico (MO); en estos casos puede ser complicado diferenciar entre una NM y una enfermedad por cambios mínimos (ECM). Recientemente se está extendiendo el estudio con C4d por inmunohistoquímica. Existe muy poca información sobre el depósito de C4d en la NM. Nuestro estudio consistió en analizar si el depósito de C4d realizado en la muestra en parafina podría ser útil en el diagnóstico de NM. Material y métodos: Estudio retrospectivo que incluyó a todos los pacientes diagnosticados de NM mediante biopsia renal en nuestra unidad entre enero de 2001 y octubre de 2008. Se incluyeron sólo adultos con un diagnóstico certero de NM y ECM idiopática que dispusieran de estudios con MO, IF y ME. En octubre de 2008, secciones de 3 µm de tejido renal fijado en formaldehído fueron deparafinadas y rehidratadas. Después se tiñeron mediante inmunohistoquímica con C4d usando un anticuerpo policlonal antihumano obtenido de conejo. Resultados: Se incluyeron finalmente 19 pacientes con ECM y 21 con NM. Ningún depósito de C4d fue observado en ninguno de los glomérulos de los pacientes con ECM y el 100% de estos pacientes fueron clasificados como negativos. Sin embargo, el depósito de C4d se detectó en el 100% de los pacientes con NM y en todos los glomérulos con una distribución uniforme y granular dibujando todas las asas capilares. Conclusiones: El depósito de C4d mediante inmunohistoquímica es una herramienta muy útil en el diagnóstico de NM (AU)

Introduction: membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults. The diagnosis is based on typical findings observed using electron microscope (EM) and immunofluorescence (IF) studies. On some occasions, tissues are only available for analysis using an optical microscope (OM); in these cases, it can be difficult to differentiate between MN and minimal change disease (MCD). Recently, the use of C4d immunohistochemical staining has spread. Very little information is available regarding C4d deposits in MN. Our study consisted of analysing whether C4d staining of samples embedded in paraffin could be useful for diagnosing MN. Material and Method: Ours was a retrospective study including all patients diagnosed with MN by renal biopsy in our unit between January 2001 and October 2008. We only included adult patients with a definitive diagnosis of MN or idiopathic MCD by OM, IF, and ME studies. In October 2008, 3µm sections of renal tissue fixed in formaldehyde were removed from paraffin and rehydrated. The samples were then stained for C4d immunohistochemical analysis using anti-human polyclonal antibodies obtained from rabbits. Results: Our study included a final sample of 19 patients with MCD and 21 with MN. No C4d deposits were observed in any of the glomeruli in patients with MCD, and 100% of these patients were classified as negative. However, C4d deposits were detected in 100% of patients with MN, and were observable in all glomeruli with a uniform granular distribution, demarcating all capillary loops. Conclusions: C4d immunohistochemical staining is a very useful tool for diagnosing MN (AU)