Keri E. Lunsford

Evidence for tissue-directed immune responses: analysis of CD4- and CD8-dependent alloimmunity.

Background. Transplant rejection has generally been considered a CD4+ T–cell-dependent immune process. CD4-independent, CD8+ T-cell rejection pathways have recently gained attention because of their relative resistance to immunosuppression. In the current study, the role of the allograft tissue in activation of these distinct pathways was examined by comparing host-immune responses with allogeneic pancreatic islets or hepatocytes transplanted across the same genetic disparity. Methods. To compare activation of CD4-dependent versus CD8-dependent alloimmunity, islets or hepatocytes retrieved from FVB/N (H-2q) mice were transplanted into CD8+ or CD4+ T–cell-reconstituted severe combined immunodeficiency mice, CD4 or CD8 knockout (KO) mice, and anti-CD4 monoclonal antibody (mAb) or anti-CD8 mAb treated C57BL/6 mice (all H-2b). The ability to immunomodulate CD4-dependent allograft rejection (in CD8 KO mice) was examined in the context of several mechanistically distinct immunotherapeutic strategies, including anti-CD4 mAb, donor-specific transfusion and anti-CD154 mAb, and anti-lymphocyte function-associated antigen-1 mAb. Results. The studies demonstrate that, whereas hepatocytes evoke alloreactive CD4-dependent and (CD4-independent) CD8+ T-cell immune responses, allogeneic islets only activate CD4-dependent immune pathways. CD4-dependent host-immune responses initiated by pancreatic islet allografts were readily suppressed by a variety of short-term immunotherapies, whereas hepatocyte-initiated CD4-dependent alloimmune responses were not. Conclusions. These results demonstrate that immune characteristics of the specific allograft tissue uniquely influence the pattern of host immune responses such that the propensity to activate CD4- or CD8-dependent alloimmune responses can be distinguished. Furthermore, CD4-dependent immune responses activated by different tissues from the same donor strain are distinguished by their susceptibility to specific immunotherapy.

Critical Role of Effector Macrophages in Mediating CD4-Dependent Alloimmune Injury of Transplanted Liver Parenchymal Cells

Despite the recognition that humoral rejection is an important cause of allograft injury, the mechanism of Ab-mediated injury to allograft parenchyma is not well understood. We used a well-characterized murine hepatocellular allograft model to determine the mechanism of Ab-mediated destruction of transplanted liver parenchymal cells. In this model, allogeneic hepatocytes are transplanted into CD8-deficient hosts to focus on CD4-dependent, alloantibody-mediated rejection. Host serum alloantibody levels correlated with in vivo allospecific cytotoxic activity in CD8 knockout hepatocyte rejector mice. Host macrophage depletion, but not CD4+ T cell, NK cell, neutrophil, or complement depletion, inhibited in vivo allocytotoxicity. Recipient macrophage deficiency delayed CD4-dependent hepatocyte rejection and inhibited in vivo allocytotoxicity without influencing alloantibody production. Furthermore, hepatocyte coincubation with alloantibody and macrophages resulted in Ab-dependent hepatocellular cytotoxicity in vitro. These studies are consistent with a paradigm of acute humoral rejection in which CD4+ T cell-dependent alloantibody production results in the targeting of transplanted allogeneic parenchymal cells for macrophage-mediated cytotoxic immune damage. Consequently, strategies to eliminate recipient macrophages during CD4-dependent rejection pathway may prolong allograft survival.

CD4+ T-cell-dependent immune damage of liver parenchymal cells is mediated by alloantibody

Background. Allogeneic hepatocytes initiate both CD4- and CD8-dependent rejection responses. The current studies address the hypothesis that acute damage of allogeneic liver parenchymal cells by the CD4-dependent pathway is alloantibody-mediated and examines immune conditions which promote activation of this pathway. Methods. The role of alloantibody in CD4-dependent hepatocyte rejection was evaluated by assessing hepatocyte (FVB/N, H-2q) survival in CD8-depleted B-cell knockout (KO) (H-2b) recipients and by monitoring hepatocyte survival in C57BL/6.SCID (H-2b) recipients transfused with donor-reactive alloantibody. The development of donor-reactive alloantibody in C57BL/6 (H-2b), CD8-depleted C57BL/6, CD8 KO (H-2b), IFN-&ggr; KO (H-2b), perforin KO (H-2b), and FasL mutant gld/gld (H-2b) hepatocyte recipients was assessed. Results. Hepatocyte rejection in B-cell KO mice was significantly delayed by CD8+ T-cell depletion (median survival time [MST], 35 days) when compared to untreated (MST, 8 days) and CD4-depleted (MST, 10 days) recipient mice. Transfusion of donor-reactive alloantibody into SCID recipients with functional hepatocellular allografts was sufficient to precipitate rejection in a dose-dependent fashion. Donor-reactive alloantibody was minimal in the serum of C57BL/6 hepatocyte recipients, but was produced in significant quantities in hepatocyte recipients genetically deficient in or depleted of CD8+ T cells and in recipients with impaired cytotoxic effector mechanisms. In addition, recipients with defects in Th1 immunity, such as IFN-&ggr; KO recipients, also produced readily detectable alloantibody. Conclusions. Collectively, these data support the hypothesis that acute immune damage of allogeneic hepatocytes by the CD4-dependent pathway is mediated by alloantibody and that this pathway is favored when Th1- or cell-mediated cytotoxic effector immune mechanisms are impaired.

Avoiding Futility in Simultaneous Liver-kidney Transplantation: Analysis of 331 Consecutive Patients Listed for Dual Organ Replacement.

Objective: We sought to evaluate outcomes and predictors of renal allograft futility (RAF—patient death or need for renal replacement therapy at 3 months) after simultaneous liver-kidney transplantation (SLKT). Background: Model for End-Stage Liver Disease (MELD) prioritization of liver recipients with renal dysfunction has significantly increased utilization of SLKT. Data on renal outcomes after SLKT in the highest MELD recipients are scarce, as are accurate predictors of recovery of native kidney function. Without well-established listing guidelines, SLKT potentially wastes renal allografts in both high-acuity liver recipients at risk for early mortality and recipients who may regain native kidney function. Methods: A retrospective single-center multivariate regression analysis was performed for adult patients undergoing SLKT (January 2004 to August 2014) to identify predictors of RAF. Results: Of 331 patients dual-listed for SLKT, 171 (52%) expired awaiting transplant, 145 (44%) underwent SLKT, and 15 (5%) underwent liver transplantation alone. After SLKT, 39% experienced delayed graft function and 20.7% had RAF. Compared with patients without RAF, RAF recipients had greater MELD scores, length of hospitalization, intraoperative base deficit, incidence of female donors, kidney and liver donor risk indices, kidney cold ischemia, and inferior overall survival. Multivariate predictors of RAF included pretransplant dialysis duration, kidney cold ischemia, kidney donor risk index, and recipient hyperlipidemia. Conclusions: With 20% short-term loss of transplanted kidneys after SLKT, our data strongly suggest that renal transplantation should be deferred in liver recipients at high risk for RAF. Consideration for a kidney allocation variance to allow for delayed renal transplantation after liver transplantation may prevent loss of scarce renal allografts.

Single-site laparoscopic living donor nephrectomy offers comparable perioperative outcomes to conventional laparoscopic living donor nephrectomy at a higher cost.

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Recent advances in immunosuppressive therapy for prevention of renal allograft rejection.

Purpose of reviewCurrent immunosuppressive therapies are highly successful at regulating acute allograft rejection and inducing long-term transplanted kidney survival; however, currently available medications are associated with generalized immune suppression and drug toxicities, including nephrotoxicity. In recent years, advances in immunosuppression that target specific pathways involved in immune activation have been developed. Recent findingsIn particular, promising medications are currently under evaluation that target ischemia-reperfusion injury as well as the cellular and humoral branches of the adaptive immune response. Targets of T-cell-mediated activation include antibodies and fusion proteins interfering with LFA-1/ICAM-1, CD2/LFA-3, CD40/CD154, and CD28/B7.1 and B7.2 interactions. Intracellular targets involved in T- and B-cell activation pathways are being evaluated, including protein kinase C inhibitors, Janus-associated kinase (JAK) inhibitors, and proteasome inhibitors. Several new medications demonstrate promise in inhibiting donor-directed humoral immunity by targeting B-cell-activating factor (BAFF) and complement activation pathways. SummaryThe present review evaluates the recent clinical advances in immunosuppressive therapies for kidney transplantation. Publications regarding advances in immunosuppressive therapies over the past year were evaluated in the context of the specific immune pathways involved in allograft rejection.

Predicting Mortality in Patients Developing Recurrent Hepatocellular Carcinoma After Liver Transplantation: Impact of Treatment Modality and Recurrence Characteristics.

Objective: To evaluate predictors of mortality and impact of treatment in patients developing recurrent hepatocellular carcinoma (HCC) following liver transplantation (LT). Summary of Background Data: Despite well-described clinicopathologic predictors of posttransplant HCC recurrence, data on prognosis following recurrence are scarce. Methods: Multivariate predictors of mortality following HCC recurrence were identified to develop a risk score model to stratify prognostic subgroups among 106 patients developing posttransplant recurrence from 1984 to 2014, including analysis of recurrence treatment modality on survival. Results: Of 857 patients undergoing LT, 106 (12.4%) developed posttransplant HCC recurrence (median 15.8 months following LT) with a median post-recurrence survival of 10.6 months. Patients receiving surgical therapy (n = 25) had a median survival of 27.8 months, significantly superior to patients receiving nonsurgical therapy (10.6 months) and best supportive care (3.7 months, P < 0.001). Multivariate predictors of mortality following recurrence included model for end-stage liver disease at LT >23, time to recurrence, >3 recurrent nodules, maximum recurrence size, bone recurrence, alphafetoprotein at recurrence, donor serum sodium, and pretransplant recipient neutrophil–lymphocyte ratio. A risk score model based on multivariate predictors accurately stratified recurrent HCC patients into prognostic subgroups, with low-risk patients (<10 points) demonstrating excellent median survival of 70.6 months, significantly superior to the medium-risk (12.2 months, 10–16 points) and high-risk (3.4 months, >16 points) groups (C-statistic 0.75, P < 0.001). Conclusions: In the largest single-center report of recurrent HCC following LT, surgical treatment in well-selected patients is associated with significantly improved survival and should be pursued. A risk score model accurately stratifies prognostic subgroups, and may help guide treatment strategies.

Dangerous dietary supplements: Garcinia cambogia-associated hepatic failure requiring transplantation

Commercial dietary supplements are marketed as a panacea for the morbidly obese seeking sustainable weight-loss. Unfortunately, many claims cited by supplements are unsupported and inadequately regulated. Most concerning, however, are the associated harmful side effects, often unrecognized by consumers. Garcinia cambogia extract and Garcinia cambogia containing products are some of the most popular dietary supplements currently marketed for weight loss. Here, we report the first known case of fulminant hepatic failure associated with this dietary supplement. One active ingredient in this supplement is hydroxycitric acid, an active ingredient also found in weight-loss supplements banned by the Food and Drug Administration in 2009 for hepatotoxicity. Heightened awareness of the dangers of dietary supplements such as Garcinia cambogia is imperative to prevent hepatoxicity and potential fulminant hepatic failure in additional patients.

Innate Pathways of Immune Activation in Transplantation

Studies of the immune mechanisms of allograft rejection have predominantly focused on the adaptive immune system that includes T cells and B cells. Recent investigations into the innate immune system, which recognizes foreign antigens through more evolutionarily primitive pathways, have demonstrated a critical role of the innate immune system in the regulation of the adaptive immune system. Innate immunity has been extensively studied in its role as the hosts first-line defense against microbial pathogens; however, it is becoming increasingly recognized for its ability to also recognize host-derived molecules that result from tissue damage. The capacity of endogenous damage signals acting through the innate immune system to lower immune thresholds and promote immune recognition and rejection of transplant grafts is only beginning to be appreciated. An improved understanding of these pathways may reveal novel therapeutic targets to decrease graft alloreactivity and increase graft longevity.

Simultaneous liver-kidney transplantation or liver transplantation alone for patients in need of liver transplantation with renal dysfunction.

Purpose of reviewThere have been no well defined guidelines to determine whether a kidney transplant should be offered to liver transplant candidates who have chronic kidney disease (CKD) or prolonged acute kidney injury while awaiting a liver transplant. This article provides a review of current literature on risk factors for CKD progression after liver transplantation alone (LTA) in patients with pretransplant renal dysfunction and the utility of cystatin C (Cyst C) to assess renal function in cirrhotic patients. Studies evaluating risk factors for transplant futility are also discussed. Based on available literature and existing consensus guidelines, a proposed algorithm for simultaneous liver–kidney transplantation (SLKT) or LTA is formulated. Recent findingsIn LTA recipients with pretransplant renal dysfunction, diabetes mellitus and type 2 hepatorenal syndrome are associated with CKD progression posttransplant. Coexisting diabetes and stages 3–4 CKD increase end-stage renal disease risk. Cyst C may be a better marker of renal function in cirrhotics. In LTA recipients, very high MELD scores and the concomitant presence of multiple comorbidities increase liver transplant futility risk. Similar studies in SLKT recipients are lacking. SummaryPretransplant diabetes status should be incorporated into future guidelines for SLKT, whereas simultaneous kidney transplantation should be deferred in highest acuity SLKT candidates with high kidney transplant futility risk. Cyst C-based equations may allow clinicians to better select the most appropriate candidates for SLKT or LTA. Further studies are needed.