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Background: There is limited information about the utility of donor-specific antibody (DSA) against HLA monitoring and the role of protocol kidney biopsy for de novo DSA (dnDSA) in simultaneous liver and kidney (SLK) transplant recipients., Methods: We analyzed SLK transplant recipients transplanted between January 2005 and December 2017, who had DSA checked posttransplant. Patients were divided into 2 groups based on whether they developed dnDSA posttransplant (dnDSA+) or not (dnDSA-). Kidney graft rejection ±45 d of dnDSA and a kidney death-censored graft survival were the primary endpoints., Results: A total of 83 SLK transplant recipients fulfilled our selection criteria. Of those, 23 were dnDSA+ and 60 were dnDSA-. Twenty-two of 23 dnDSA+ patients had DSA against class II HLA, predominantly against DQ. Fifteen recipients underwent kidney biopsy ±45 d of dnDSA. Six of these were clinically indicated due to kidney graft dysfunction. The other 9 had a protocol kidney biopsy only due to dnDSA, and 6 of these 9 had a rejection. Also, 3 recipients had sequential biopsies of both the kidney and liver grafts. Among those with sequential biopsies of both grafts, there was a difference between the organs in the rate and types of rejections. At last follow up, dnDSA was not associated with graft failure of either the kidney or liver., Conclusions: Although our study was limited by a small sample size, it suggests the potential utility of DSA monitoring and protocol kidney biopsy for dnDSA., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

The aryl hydrocarbon receptor (AHR), which has been central to studies in toxicology for years as the receptor for the toxicant dioxin, is rapidly gaining interest in immunology based on its ability to influence T-cell differentiation. Multiple studies have documented that binding of this receptor with certain ligands favors T-cell differentiation toward regulatory T cells, and paradoxically, binding of this same receptor with different ligands enhances Th17 effector cell differentiation. This finding has been confirmed in both in vitro and in vivo models, where different ligands are able to either ameliorate or conversely aggravate autoimmunity in experimental autoimmune encephalomyelitis. The AHR has both an endogenous role that is important in development and normal physiology and an exogenous role as a receptor for manmade toxicants, with their binding leading to transcription of cytochrome P450 enzymes that metabolize these same ligands. Based on recent reports that will be summarized in this overview, we will consider the role that the AHR might play as a sensor to the outside environment, leading to alteration of the acquired immune system that might have relevance in transplantation or other medical conditions. In addition to describing the data in normal physiology and T-cell differentiation, we will present examples of the importance of this receptor in preclinical models of disease and highlight specific ligands that target the AHR and will have efficacy in treating transplant rejection and in tolerance protocols.