Chronic-active antibody-mediated rejection (c-aABMR) is defined as histological evidence of chronic endothelial injury (cg), also known as transplant glomerulopathy, and either microvascular inflammation (MVI) or positivity for C4d. Importantly, the presence of donor-specific antibodies (DSA) is currently still mandatory for the diagnosis of c-aABMR. This retrospective study of 41 c-aABMR patients investigates whether cases suspicious for c-aABMR (DSA negative, n = 24) differ from cases of c-aABMR (DSA positive, n = 17) with respect to renal histology, allograft function and long-term graft survival. All included patients had progressive loss of allograft function and were diagnosed by for cause biopsy and scored according to the Banff '15 criteria. In all DSApos cases, DSA were de novo and the majority was directed against HLA-II being mostly anti-HLA-DQ antibodies. There were no statistically significant differences in clinical characteristics, decline in allograft function and renal allograft survival in cases with or without DSAs. All cases showed chronic histomorphological damage and inflammation, irrespective of the presence of DSA. Renal histology and clinical outcome of patients suspicious for c-aABMR (DSAneg) do not significantly differ from patients with a diagnosis of c-aABMR (DSApos). We believe that our study adds to the ongoing debate regarding the need for DSAs to be present for the diagnosis of c-aABMR.

BackgroundChronic active antibody mediated rejection (c-aABMR) is a major cause of long-term kidney allograft loss. It is hypothesized that frequent sub-therapeutic exposure to immunosuppressive drugs, in particular tacrolimus (Tac), is a risk factor for the development of c-aABMR. The intra-patient variability (IPV) in Tac exposure may serve as a substitute biomarker for underexposure and/or non-adherence. In this study, the association between Tac IPV and the development of c-aABMR was investigated.MethodsWe retrospectively included 59 patients diagnosed with c-aABMR and compared them to 189 control patients matched for age, year of transplantation and type of kidney donor. The Tac IPV was calculated from pre-dose tacrolimus concentrations measured over a 3 year period preceding the diagnosis of c-aABMR. The mean Tac predose concentrations (C0), Tac IPV, renal allograft function and graft survival were compared between the groups.ResultsTac IPV was 24.4% for the cases versus 23.6% for the controls (p = 0.47). The mean Tac C0 was comparable for the cases (5.8 ng/mL) and control patients (6.1 ng/mL, p = 0.08). Only in the c-aABMR group a significant decline in both mean Tac C0 and allograft function over the timespan of 3 years was observed (p = 0.03 and p<0.001). Additionally, in the group of c-aABMR patients a high IPV was associated with inferior graft survival (p = 0.03).ConclusionsA high Tac IPV per se does not predispose to the development of c-aABMR but is associated with inferior graft survival once c-aABMR is diagnosed.

Background: Little is known about immune cell infiltrate type in the kidney allograft of patients with chronic-active antibody-mediated rejection (c-aABMR). Methods: In this study, multiplex immunofluorescent staining was performed on 20 cases of biopsy-proven c-aABMR. T-cell subsets (CD3, CD8, Foxp3, and granzyme B), macrophages (CD68 and CD163), B cells (CD20), and natural killer cells (CD57) were identified and counted in the glomeruli (cells/glomerulus) and the tubulointerstitial (TI) compartment [cells/high-power field (HPF)]. Results: In the glomerulus, T cells and macrophages were the dominant cell types with a mean of 5.5 CD3 + cells/glomerulus and 4 CD68 + cells/glomerulus. The majority of T cells was CD8 + (62%), and most macrophages were CD68 + CD163 + (68%). The TI compartment showed a mean of 116 CD3 + cells/HPF, of which 54% were CD8 +. Macrophage count was 21.5 cells/HPF with 39% CD68 + CD163 +. CD20 + cells were sporadically present in glomeruli, whereas B-cell aggregates in the TI compartment were frequently observed. Natural killer cells were rarely identified. Remarkably, increased numbers of CD3 + FoxP3 + cells in the TI compartment were associated with decreased graft survival (p = 0.004). Conclusions: Renal allograft biopsies showing c-aABMR show a predominance of infiltrating CD8 + T cells, and increased numbers of interstitial FoxP3 + T cells are associated with inferior allograft survival.

Chronic-active antibody mediated rejection (c-aABMR) contributes significantly to late renal allograft failure. The antibodies directed against donor-derived antigens, e.g. anti-HLA antibodies, cause inflammation at the level of the microvascular endothelium. This is characterized by signs of local activation of the complement system and accumulation of immune cells within the capillaries. Non-invasive biomarkers of c-aABMR are currently not available but could be valuable for early detection. We therefore analyzed the activation profiles of circulating T and B cells, NK cells and monocytes in the peripheral blood of 25 kidney transplant recipients with c-aABMR and compared them to 25 matched recipients to evaluate whether they could serve as a potential biomarker. No significant differences were found in the total percentage and distribution of NK cells, B cells and T cells between the c-aABMRpos and c-aABMRneg cases. There was however a higher percentage of monocytes present in c-aABMRpos cases (p < .05). Additionally, differences were found in activation status of circulating monocytes, NK cells and γδ T cells, mainly concerning the activation marker CD16. Although statistically significant, these differences were not sufficient for use as a biomarker of c-aABMR.

Background Chronic-active antibody mediated rejection (c-aABMR) is a major contributor to long-term kidney allograft loss. We conducted a retrospective analysis to establish the efficacy of treatment with intravenous immunoglobulins (IVIG) and pulse methylprednisolone (MP) of patients with c-aABMR. Methods Sixty-nine patients, in the period 2005–2017, with the diagnosis (suspicious for) c-aABMR that were treated with IVIG and MP were included. Patients were administered three doses of 1 g intravenous MP combined with a single dose of IVIG (1 g/kg body weight). Primary outcome was the decline in allograft function one year post treatment. Responders to IVIG-MP therapy were defined by an eGFR one year after treatment which was at least 25% above the projected allograft function. Results Patients showed an average decline in eGFR of 9.8 ml/min/1.73m 2 the year prior to treatment. Following treatment, a significant reduction ( p < 0.001) in eGFR decline was observed (6.3 ml/min/1.73m 2 ). Furthermore, a significant improvement in proteinuria was observed upon treatment ( p < 0.001). Sixty-two percent ( n = 43) of the patients were considered a responder and showed considerable slowing of graft function deterioration in the year after treatment ( p < 0.001). Three and 5-year graft survival was significantly superior in responders. Conclusions More than 60% of patients with c-aABMR with a progressive decline in eGFR respond favorably to treatment with IVIG-MP resulting in a significant improvement of graft survival (Sablik, Am J Transplant 18, 2018). Electronic supplementary material The online version of this article (10.1186/s12882-019-1385-z) contains supplementary material, which is available to authorized users.