Absence of FcγRIII results in increased proinflammatory response in FcγRIII-KO cardiac recipients

Human amniotic mesenchymal stem cells inhibit immune rejection injury from allogeneic mouse heart transplantation: A preliminary study on the microRNA expression

BACKGROUND

Mesenchymal stem cell therapy is a new treatment for immune rejection in heart transplantation. The aim of this paper is to investigate the effect of human amniotic mesenchymal stem cells (hAMSCs) on alleviating immune rejection of allogeneic heart transplantation in mice and its possible underlying mechanism.

METHODS

We injected hAMSCs into cervical ectopic heart transplantation model mice via tail vein to observe the survival time, the pathological changes of donor myocardium, and the fluorescent distribution of hAMSCs after the transplantation. MicroRNAs (miRs) with significantly differential expression were obtained by RNA sequencing and bioinformatic analysis, and a dual luciferase reporter gene assay together with real-time quantitative PCR (qRT-PCR) was performed to verify the relationship between miRs and their targeting genes.

RESULTS

The intervention of hAMSCs prolonged the graft survival time and alleviated the pathological damage of the donor heart. The injected hAMSCs were distributed mainly in the liver, spleen, and kidney, only a very small portion in the donor and recipient hearts. In the allogeneic transplantation models, the expression of miR-34b-5p significantly increased after hAMSC treatment. MiR-34b-5p showed a knockdown effect on gene Fc gamma receptor 2B (FCGR2B).

CONCLUSIONS

hAMSCs can reduce the immune rejection injury after allogeneic heart transplantation. This effect may be associated with the upregulation of miR-34b-5p expression to knock down its targeting gene FCGR2B.

Neutrophil diversity and plasticity: Implications for organ transplantation

Neutrophils, as the first defenders against external microbes and stimuli, are highly active and finely regulated innate immune cells. Emerging evidence has challenged the conventional dogma that neutrophils are a homogeneous population with a short lifespan that promotes tissue damage. Recent findings on neutrophil diversity and plasticity in homeostatic and disease states have centered on neutrophils in the circulation. In contrast, a comprehensive understanding of tissue-specialized neutrophils in health and disease is still lacking. This article will first discuss how multiomics advances have contributed to our understanding of neutrophil heterogeneity and diversification in resting and pathological settings. This discussion will be followed by a focus on the heterogeneity and role of neutrophils in solid organ transplantation and how neutrophils may contribute to transplant-related complications. The goal of this article is to provide an overview of the research on the involvement of neutrophils in transplantation, with the aim that this may draw attention to an underappreciated area of neutrophil research.

Critical Role of Macrophage FcγR Signaling and Reactive Oxygen Species in Alloantibody-Mediated Hepatocyte Rejection

Humoral alloimmunity negatively impacts both short- and long-term cell and solid organ transplant survival. We previously reported that alloantibody-mediated rejection of transplanted hepatocytes is critically dependent on host macrophages. However, the effector mechanism(s) of macrophage-mediated injury to allogeneic liver parenchymal cells is not known. We hypothesized that macrophage-mediated destruction of allogeneic hepatocytes occurs by cell-cell interactions requiring FcγRs. To examine this, alloantibody-dependent hepatocyte rejection in CD8-depleted wild-type (WT) and Fcγ-chain knockout (KO; lacking all functional FcγR) transplant recipients was evaluated. Alloantibody-mediated hepatocellular allograft rejection was abrogated in recipients lacking FcγR compared with WT recipients. We also investigated anti-FcγRI mAb, anti-FcγRIII mAb, and inhibitors of intracellular signaling (to block phagocytosis, cytokines, and reactive oxygen species [ROS]) in an in vitro alloantibody-dependent, macrophage-mediated hepatocytoxicity assay. Results showed that in vitro alloantibody-dependent, macrophage-mediated hepatocytotoxicity was critically dependent on FcγRs and ROS. The adoptive transfer of WT macrophages into CD8-depleted FcγR-deficient recipients was sufficient to induce alloantibody-mediated rejection, whereas adoptive transfer of macrophages from Fcγ-chain KO mice or ROS-deficient (p47 KO) macrophages was not. These results provide the first evidence, to our knowledge, that alloantibody-dependent hepatocellular allograft rejection is mediated by host macrophages through FcγR signaling and ROS cytotoxic effector mechanisms. These results support the investigation of novel immunotherapeutic strategies targeting macrophages, FcγRs, and/or downstream molecules, including ROS, to inhibit humoral immune damage of transplanted hepatocytes and perhaps other cell and solid organ transplants.

Mechanisms of antibody-mediated acute and chronic rejection of kidney allografts

PURPOSE OF REVIEW

Antibody-mediated rejection is responsible for up to half of acute rejection episodes in kidney transplant patients and more than half of late graft failures. Antibodies cause acute graft abnormalities that are distinct from T cell-mediated rejection and at later times posttransplant, a distinct pathologic lesion is associated with capillary basement membrane multilayering and glomerulopathy. Despite the importance of donor-reactive antibodies as the leading cause of kidney graft failure, mechanisms underlying antibody-mediated acute and chronic kidney graft injury are poorly understood. Here, we review recent insights provided from clinical studies as well as from animal models that may help to identify new targets for therapy.

RECENT FINDINGS

Studies of biopsies from kidney grafts in patients with donor-specific antibody versus those without have utilized analysis of pathologic lesions and gene expression to identify the distinct characteristics of antibody-mediated rejection. These analyses have indicated the presence of natural killer cells and their activation during antibody-mediated rejection. The impact of studies of antibody-mediated allograft injury in animal models have lagged behind these clinical studies, but have been useful in testing the activation of innate immune components within allografts in the presence of donor-specific antibodies.

SUMMARY

Most insights into processes of antibody-mediated rejection of kidney grafts have come from carefully designed clinical studies. However, several new mouse models of antibody-mediated kidney allograft rejection may replicate the abnormalities observed in clinical kidney grafts and may be useful in directly testing mechanisms that underlie acute and chronic antibody-mediated graft injury.

Impact of Temperature on Porcine Liver Machine Perfusion From Donors After Cardiac Death

Normothermic machine perfusion (NMP) has been introduced as a promising technology to preserve and possibly repair marginal liver grafts. The aim of this study was to compare the effect of temperature on the preservation of donation after cardiac death (DCD) liver grafts in an ex vivo perfusion model after NMP (38.5°C) and subnormothermic machine perfusion (SNMP, 21°C) with a control group preserved by cold storage (CS, 4°C). Fifteen porcine livers with 60 min of warm ischemia were preserved for 10 h by NMP, SNMP or CS (n = 5/group). After the preservation phase all livers were reperfused for 24 h in an isolated perfusion system with whole blood at 38.5°C to simulate transplantation. At the end of transplant simulation, the NMP group showed significantly lower hepatocellular enzyme level (AST: 277 ± 69 U/L; ALT: 22 ± 2 U/L; P < 0.03) compared to both SNMP (AST: 3243 ± 1048 U/L; ALT: 127 ± 70 U/L) and CS (AST: 3150 ± 1546 U/L; ALT: 185 ± 97 U/L). There was no significant difference between SNMP and CS. Bile production was significantly higher in the NMP group (219 ± 43 mL; P < 0.01) compared to both SNMP (49 ± 84 mL) and CS (12 ± 16 mL) with no significant difference between the latter two groups. Histologically, the NMP livers showed preserved cellular architecture compared to the SNMP and CS groups. NMP was able to recover DCD livers showing superior hepatocellular integrity, biliary function, and microcirculation compared to SNMP and CS. SNMP showed some significant benefit over CS, yet has not shown any advantage over NMP.

Contribution of Fcγ receptors to human respiratory syncytial virus pathogenesis and the impairment of T-cell activation by dendritic cells

Human respiratory syncytial virus (hRSV) is the leading cause of infant hospitalization related to respiratory disease. Infection with hRSV produces abundant infiltration of immune cells into the airways, which combined with an exacerbated pro-inflammatory immune response can lead to significant damage to the lungs. Human RSV re-infection is extremely frequent, suggesting that this virus may have evolved molecular mechanisms that interfere with host adaptive immunity. Infection with hRSV can be reduced by administering a humanized neutralizing antibody against the virus fusion protein in high-risk infants. Although neutralizing antibodies against hRSV effectively block the infection of airway epithelial cells, here we show that both, bone marrow-derived dendritic cells (DCs) and lung DCs undergo infection with IgG-coated virus (hRSV-IC), albeit abortive. Yet, this is enough to negatively modulate DC function. We observed that such a process is mediated by Fcγ receptors (FcγRs) expressed on the surface of DCs. Remarkably, we also observed that in the absence of hRSV-specific antibodies FcγRIII knockout mice displayed significantly less cellular infiltration in the lungs after hRSV infection, compared with wild-type mice, suggesting a potentially harmful, IgG-independent role for this receptor in hRSV disease. Our findings support the notion that FcγRs can contribute significantly to the modulation of DC function by hRSV and hRSV-IC. Further, we provide evidence for an involvement of FcγRIII in the development of hRSV pathogenesis.

FcγR requirements leading to successful immunotherapy

Monoclonal antibody (mAb) immunotherapy is currently experiencing an unprecedented amount of success, delivering blockbuster sales for the pharmaceutical industry. Having experienced several false dawns and overcoming technical issues which limited progress, we are now entering a golden period where mAbs are becoming a mainstay of treatment regimes for diseases ranging from cancer to autoimmunity. In this review, we discuss how these mAbs are most likely working and focus in particular on the key receptors that they interact with to precipitate their therapeutic effects. Although their targets may vary, their engagement with Fcγ receptors (FcγRs) on numerous immune effector cells is almost universal, and here we review their roles in delivering successful immunotherapy.

Acute and chronic rejection: compartmentalization and kinetics of counterbalancing signals in cardiac transplants

Acute and chronic rejection impact distinct compartments of cardiac allografts. Intramyocardial mononuclear cell infiltrates define acute rejection, whereas chronic rejection affects large arteries. Hearts transplanted from male to female C57BL/6 mice undergo acute rejection with interstitial infiltrates at 2 weeks that resolve by 6 weeks when large arteries develop arteriopathy. These processes are dependent on T cells because no infiltrates developed in T cell-deficient mice and transfer of CD4 T cells restored T cell as well as macrophage infiltrates and ultimately neointima formation. Markers of inflammatory macrophages were up-regulated in the interstitium acutely and decreased as markers of wound healing macrophages increased chronically. Programmed cell death protein, a negative costimulator, and its ligand PDL1 were up-regulated in the interstitium during resolution of acute rejection. Blocking PDL1:PD1 interactions in the acute phase increased interstitial T cell infiltrates. Toll-like receptor (TLR) 4 and its endogenous ligand hyaluronan were increased in arteries with neointimal expansion. Injection of hyaluronan fragments increased intragraft production of chemokines. Our data indicate that negative costimulatory pathways are critical for the resolution of acute interstitial infiltrates. In the arterial compartment recognition of endogenous ligands including hyaluronan by the innate TLRs may support the progression of arteriopathy.

The anti-lymphoma activities of anti-CD137 monoclonal antibodies are enhanced in FcγRIII(-/-) mice

Agonistic monoclonal antibodies (mAbs) directed against the co-signaling molecule CD137 (4-1BB) elicit potent anti-tumor immunity in mice. This anti-tumor immunity has traditionally been thought to result from the ability of the Fab portion of anti-CD137 to function as an analog for CD137L. Although binding of CD137 by anti-CD137 mAbs has the potential to cross-link the Fc fragments, enabling Fc engagement of low to moderate affinity Fc gamma receptors (FcγR), the relative import of such Fc-FcγR interactions in mediating anti-CD137 associated anti-tumor immunity is unknown. We studied the ability of a rat anti-mouse CD137 mAb (2A) to mediate the anti-tumor response against the EL4E7 lymphoma in WT and FcγR(-/-) strains. 2A-treated FcRγ(-/-) mice had improved anti-tumor immunity against EL4E7, which could be completely recapitulated in FcγRIII(-/-) animals. These improved anti-tumor responses were associated with increased splenic CD8β T cell and dendritic cell (DC) populations. Furthermore, there was an increase in the number of DCs expressing high levels of the CD40, CD80, and CD86 molecules that are associated with more effective antigen presentation. Our results demonstrate an unexpected inhibitory role for FcγRIII in the anti-tumor function of anti-CD137 and underscore the need to consider antibody isotype when engineering therapeutic mAbs.

Expression of HSPA12B in acute cardiac allograft rejection in rats

HSP70 may play a more important role in regulating antigen-specific immune response than other HSPs; however, HSPA12B production in transplanted heart remains obscure, which was identified as the newest member of the HSP70 family. In the current study, we performed a heart transplantation model in adult rats and investigated the dynamic changes of HSPA12B expression in the cardiac grafts. The cardiac grafts of allogeneic (Wistar-Lewis rat) and syngeneic (Lewis-Lewis rat) rat models were subjected to histopathological and immunohistochemical analyses for HSPA12B expression on days 0-7 after operation. We also examined the expression profiles of active caspase-3, whose changes were correlated with the expression profiles of HSPA12B. Our results demonstrated that HSPA12B protein exhibited biphasic patterns in transplanted heart. The first expression phase correlated with ischemical reperfusion injury over 2 days post-transplant. The second peak of HSPA12B expression was found only in allografts on day 5, concurrent with the expression of caspase-3. Immunohistochemical assay showed that compared with rare expression in isografts, there were significant protein expressions of HSPA12B and caspase-3 in heart allografts from day 5 to 7 post-transplant. Furthermore, double immunofluorescence staining for active caspase-3 and HSPA12B in isografts and allografts at day 5 post-transplant were analyzed and colocalization of HSPA12B/active caspase-3 was detected in allografts. In conclusion, this is the first description of HSPA12B expression in acute cardiac allograft rejection. Our results suggested that HSPA12B might play crucial roles in heart pathophysiology after transplantation.