Intra-operative kinetics of anti-HLA antibody in simultaneous liver-kidney transplantation

During simultaneous liver-kidney transplantation (SLK) in highly sensitized patients, donor specific anti-human leukocyte antigen antibodies (DSA, HLA) can be present prior to transplant leading to positive crossmatch, yet these recipients have relatively low incidences of acute rejection. The mechanisms and timing underlying immunologic changes that occur intra-operatively remain largely unknown. Therefore, we measured the intra- and peri-operative kinetics of anti-HLA antibodies in highly sensitized SLK recipients. In this study, pre- and post-operative blood samples were obtained from sensitized SLK candidates with documented DSA. Intra-operative samples were obtained from a sub-group of SLK recipients. Pretransplant anti-HLA antibody profiles were created and flow cytometry and anti-human globulin complement-dependent cytotoxic crossmatches were performed. Significant reductions in anti-HLA class I and II DSA were seen intra-operatively shortly after reperfusion of the liver allograft. This effect was most pronounced for anti-HLA class I DSA (mean change, −85%, p < 0.05); changes to anti-HLA class II DSA were less robust (mean change, −47%, p = 0.15). Importantly, non-DSA anti-HLA antibodies remained unchanged throughout the perioperative period, suggesting the mechanism(s) by which the liver lowers DSA levels are specific to the DSA. These data demonstrate the immunologic benefit of performing SLK is lasting and occurs very shortly after liver reperfusion.

Variations in diet cause alterations in microbiota and metabolites that follow changes in disease severity in a multiple sclerosis model

Multiple sclerosis (MS) is a metabolically demanding disease involving immune-mediated destruction of myelin in the central nervous system. We previously demonstrated a significant alteration in disease course in the experimental autoimmune encephalomyelitis (EAE) preclinical model of MS due to diet. Based on the established crosstalk between metabolism and gut microbiota, we took an unbiased sampling of microbiota, in the stool, and metabolites, in the serum and stool, from mice (Mus musculus) on the two different diets, the Teklad global soy protein-free extruded rodent diet (irradiated diet) and the Teklad sterilisable rodent diet (autoclaved diet). Within the microbiota, the genus Lactobacillus was found to be inversely correlated with EAE severity. Therapeutic treatment with Lactobacillus paracasei resulted in a significant reduction in the incidence of disease, clinical scores and the amount of weight loss in EAE mice. Within the metabolites, we identified shifts in glycolysis and the tricarboxylic acid cycle that may explain the differences in disease severity between the different diets in EAE. This work begins to elucidate the relationship between diet, microbiota and metabolism in the EAE preclinical model of MS and identifies targets for further study with the goal to more specifically probe the complex metabolic interaction at play in EAE that may have translational relevance to MS patients.

Unintended Consequences of the New National Kidney Allocation Policy in the United States

The new national Kidney Allocation System of the Organ Procurement and Transplantation Network (OPTN), effective as of December 4, 2014, was designed to improve the chances of transplanting the most highly sensitized patients on the waitlist, those with calculated panel reactive antibody values of 98%, 99% and 100%. Recently, it was suggested that these highly sensitized patients will experience inequitable access, given the reported high prevalence of antibodies to HLA-DP, and the fact that only about 1/3 of deceased donors are typed for HLA-DP antigens. Here we report that 320/2948 flow cytometric crossmatches performed for the Northwestern transplant program over the past 28 months were positive solely due to HLA-DP donor-specific antibodies (11%; 16.5% of patients with HLA antibodies-sensitized patients). We further show that 58/207 (12%) HLA-DR serologically matched donor-recipient pairs had a positive B cell flow crossmatch due to donor-specific HLA class II antibodies, and 2/34 (6%) serologic zero-HLA-A-B-DR mismatch had a positive flow crossmatch due to HLA-DSA. We therefore provide information regarding the necessity and importance of complete donor HLA typing including both chains of the HLA-DP antigen (encoded by HLA-DPA1 and HLA-DPB1) at the time of organ offer.

Assessing Antibody Strength: Comparison of MFI, C1q, and Titer Information

The presence of donor-specific HLA antibodies before or after transplantation may have different implications based on the antibody strength. Yet, current approaches do not provide information regarding the true antibody strength as defined by antigen-antibody dissociation rate. To assess currently available methods, we compared between neat mean fluorescence intensity (MFI) values, C1q MFI values, ethylenediaminetetraacetic acid (EDTA)-treated samples, as well as titration studies and peak MFI values of over 7000 Luminex-based single-antigen HLA antibody data points. Our results indicate that neat MFI values do not always accurately depict antibody strength. We further showed that EDTA treatment (6%) does not always remove all inhibitory factors compared with C1q or titration studies. In this study of patients presenting with multiple antibody specificities, a prozone effect was observed in 71% of the cohort (usually not affecting all antibody specificities within a single serum sample, though). Similar to titration studies, the C1q assay was able to address the issue of potential inhibition; however, its limitation is its low sensitivity and inability to detect the presence of weak antibodies. Titration studies are the only method among the approaches used in this study to provide information suggesting antigen-antibody dissociation rates and are, therefore, likely to provide better indication of true antibody strength.