Brain death that occurs in the setting of deceased organ donation for transplantation is associated with systemic inflammation of unknown origin. It has recently been recognized that mitochondria-derived damage-associated molecular patterns (mtDAMPs) released into the circulation in the setting of trauma and tissue injury are associated with a systemic inflammatory response. We examined the blood of deceased organ donors and found elevated levels of inflammatory cytokines and chemokines that correlated with levels of mtDAMPs. We also found that donor neutrophils are activated and that donor plasma contains a neutrophil-activating factor that is blocked by cyclosporin H, a formyl peptide receptor-1 antagonist. Examination of donor plasma by electron microscopy and flow cytometry revealed that free- and membrane-bound mitochondria are elevated in donor plasma. Interestingly, we demonstrated a correlation between donor plasma mitochondrial DNA levels and early allograft dysfunction in liver transplant recipients, suggesting a role for circulating mtDAMPs in allograft outcomes. Current approaches to prolong allograft survival focus on immune suppression in the transplant recipient; our data indicate that targeting inflammatory factors in deceased donors prior to organ procurement is another potential strategy for improving transplant outcomes.

The innate immune system is a critical regulator of the adaptive immune responses that lead to allograft rejection. It is increasingly recognized that endogenous molecules released from tissue injury and cell death are potent activators of innate immunity. Mitochondria, ancestrally related to bacteria, possess an array of endogenous innate immune‐activating molecules. We have recently demonstrated that extracellular mitochondria are abundant in the circulation of deceased organ donors and that their presence correlates with early allograft dysfunction. Here we demonstrate the ability of mitochondria to activate endothelial cells (ECs), the initial barrier between a solid organ allograft and its host. We find that mitochondria exposure leads to the upregulation of EC adhesion molecules and their production of inflammatory cytokines and chemokines. Additionally, mitochondrial exposure causes dendritic cells to upregulate costimulatory molecules. Infusion of isolated mitochondria into heart donors leads to significant increase in allograft rejection in a murine heterotopic heart transplantation model. Finally, co‐incubation of human peripheral blood mononuclear cells with mitochondria‐treated ECs results in increased numbers of effector (IFN‐γ⁺, TNF‐α⁺) CD8⁺ T cells. These data indicate that circulating extracellular mitochondria in deceased organ donors may directly activate allograft ECs and promote graft rejection in transplant recipients.

Brazilian-born British biologist Dr. Peter Medawar played an integral role in developing the concepts of immunologic rejection and tolerance, which led to him receiving the Nobel Prize “for the discovery of acquired immunologic tolerance” and eventually made organ transplantation a reality. However, at the time of his early work in tolerance, a paradox to his theories was brought to his attention; how was pregnancy possible? Pregnancy resembles organ transplantation in that the fetus, possessing paternal antigens, is a semi-allogeneic graft that can survive without immunosuppression for 9 months. To answer this question, Medawar proposed three hypotheses of how a mother supports her fetus in utero, now known as “Medawar’s Paradox.” The mechanisms that govern fetomaternal tolerance are still incompletely understood but may provide critical insight into how to achieve immune tolerance in organ transplantation. Here, we review current understanding of the immune factors responsible for fetomaternal tolerance during pregnancy and discuss the potential implications for advances in transplantation science.

Background: Serum AFP-L3%, AFP, and DCP are useful biomarkers for HCC detection, but their utility in assessing treatment response remains unknown. We aim to evaluate the accuracy of a biomarker model in the detection of posttreatment viable tumors. Methods: For model derivation, recipients with HCC undergoing liver transplant from 2018 to 2022 who had biomarkers collected within 3 months before transplant were included. We developed a generalized linear model for detecting posttreatment viable tumors with the 3 biomarkers as covariates, which we termed the “LAD Score.” An independent cohort of 117 patients with HCC was used for external validation. Results: Among 205 recipients of transplant, 70.2% had evidence of viable tumor on explant. The median LAD score was higher among patients with viable versus nonviable tumors (1.06 vs. 0.465, p < 0.001). The LAD score had a sensitivity of 55.6% and a specificity of 85.1% at the cutoff of 0.927, which was more accurate than imaging for detecting posttreatment viable tumors (AUROC 0.736 vs. 0.643, respectively; p = 0.045). The superior performance of the LAD score over imaging is primarily driven by its greater accuracy in detecting tumors <2 cm in diameter (AUROC of the LAD score 0.721 vs. imaging 0.595, p = 0.02). In the validation data set, the LAD score had an AUROC of 0.832 (95% CI: 0.753, 0.911) with a sensitivity of 72.5% and a specificity of 89.4% at the cutoff of 0.927. Conclusions: Our findings suggest the utility of LAD score in treatment response assessment after locoregional therapy for HCC, particularly in detecting small tumors. A larger prospective study is in progress to validate its accuracy and evaluate its performance in recurrence monitoring.