y Both authors contributed equally.The angiotensin II type 1 receptor (AT 1 R) is an emerging target of functional non-HLA antibodies (Ab). We examined the potential of determining the degree of presensitization against AT 1 R as a risk factor for graft survival and acute rejection (AR). The study included 599 kidney recipients between 1998 and 2007. Serum samples were analyzed in a blinded fashion for anti-AT 1 R antibodies (AT 1 R-Abs) using a quantitative solid-phase assay. A threshold of AT 1 R-Ab levels was statistically determined at 10 U based on the time to graft failure. An extended Cox model determined risk factors for occurrence of graft failure and a first AR episode. AT 1 R-Abs >10 U were detected in 283 patients (47.2%) before transplantation. Patients who had a level of AT 1 R-Abs >10 U had a 2.6-fold higher risk of graft failure from 3 years posttransplantation onwards (p ¼ 0.0005) and a 1.9-fold higher risk of experiencing an AR episode within the first 4 months of transplantation (p ¼ 0.0393). Antibody-mediated rejection (AMR) accounted for 1/3 of AR, whereby 71.4% of them were associated with >10 U of pretransplant AT 1 R-Abs. Pretransplant anti-AT 1 R-Abs are an independent risk factor for long-term graft loss in association with a higher risk of early AR episodes.

†The two first and senior authors contributed equally.We report here on a European cohort of 27 kidney transplant recipients displaying operational tolerance, compared to two cohorts of matched kidney transplant recipients under immunosuppression and patients who stopped immunosuppressive drugs and presented with rejection. We report that a lower proportion of operationally tolerant patients received induction therapy (52% without induction therapy vs. 78.3% [p = 0.0455] and 96.7% [p = 0.0001], respectively), a difference likely due to the higher proportion (18.5%) of HLA matched recipients in the tolerant cohort. These patients were also significantly older at the time of transplantation (p = 0.0211) and immunosuppression withdrawal (p = 0.0002) than recipients who rejected their graft after weaning. Finally, these patients were at lower risk of infectious disease. Among the 27 patients defined as operationally tolerant at the time of inclusion, 19 still display stable graft function (mean 9 ± 4 years after transplantation) whereas 30% presented slow deterioration of graft function. Six of these patients tested positive for pre-graft anti-HLA antibodies. Biopsy histology studies revealed an active immunologically driven mechanism for half of them, associated with DSA in the absence of C4d. This study suggests that operational tolerance can persist as a robust phenomenon, although eventual graft loss does occur in some patients, particularly in the setting of donor-specific alloantibody.

No abstract

Life-threatening graft-versus-host disease (GVHD) limits the use of HLA-C-mismatched unrelated donors in transplantation. Clinicians lack criteria for donor selection when HLA-C-mismatched donors are a patient's only option for cure. We examined the role for HLA-C expression levels to identify permissible HLA-C mismatches. The median fluorescence intensity, a proxy of HLA-C expression, was assigned to each HLA-C allotype in 1975 patients and their HLA-C-mismatched unrelated transplant donors. The association of outcome with the level of expression of patients' and donors' HLA-C allotypes was evaluated in multivariable models. Increasing expression level of the patient's mismatched HLA-C allotype was associated with increased risks of grades III to IV acute GVHD, nonrelapse mortality, and mortality. Increasing expression level among HLA-C mismatches with residue 116 or residue 77/80 mismatching was associated with increased nonrelapse mortality. The immunogenicity of HLA-C mismatches in unrelated donor transplantation is influenced by the expression level of the patient's mismatched HLA-C allotype. HLA-C expression levels provide new information on mismatches that should be avoided and extend understanding of HLA-C-mediated immune responses in human disease

The interactions of killer Ig–like receptor 2D (KIR2D) with HLA-C ligands contribute to functional NK cell education and regulate NK cell functions. Although simple alloreactive rules have been established for inhibitory KIR2DL, those governing activating KIR2DS function are still undefined, and those governing the formation of the KIR2D repertoire are still debated. In this study, we investigated the specificity of KIR2DL1/2/3 and KIR2DS1/2, dissected each KIR2D function, and assessed the impact of revisited specificities on the KIR2D NK cell repertoire formation from a large cohort of 159 KIR and HLA genotyped individuals. We report that KIR2DL2+ and KIR2DL3+ NK cells reacted similarly against HLA-C+ target cells, irrespective of C1 or C2 allele expression. In contrast, KIR2DL1+ NK cells specifically reacted against C2 alleles, suggesting a larger spectrum of HLA-C recognition by KIR2DL2 and KIR2DL3 than KIR2DL1. KIR2DS2+ KIR2DL2− NK cell clones were C1-reactive irrespective of their HLA-C environment. However, when KIR2DS2 and KIR2DL2 were coexpressed, NK cell inhibition via KIR2DL2 overrode NK cell activation via KIR2DS2. In contrast, KIR2DL1 and KIR2DS2 had an additive enhancing effect on NK cell responses against C1C1 target cells. KIR2DL2/3/S2 NK cells predominated within the KIR repertoire in KIR2DL2/S2+ individuals. In contrast, the KIR2DL1/S1 NK cell compartment is dominant in C2C2 KIR2DL2/S2− individuals. Moreover, our results suggest that together with KIR2DL2, activating KIR2DS1 and KIR2DS2 expression limits KIR2DL1 acquisition on NK cells. Altogether, our results suggest that the NK cell repertoire is remolded by the activating and inhibitory KIR2D and their cognate ligands.