Potent immunosuppressive drugs have significantly improved early patient survival after liver transplantation (LT). However, long-term results remain unsatisfactory because of adverse events that are largely associated with lifelong immunosuppression. To solve this problem, different strategies have been undertaken to induce operational tolerance, for example, maintenance of normal graft function and histology without immunosuppressive therapy, but have achieved limited success. In this pilot study, we aimed to induce tolerance using a novel regulatory T-cell-based cell therapy in living donor LT. Adoptive transfer of an ex vivo-generated regulatory T-cell-enriched cell product was conducted in 10 consecutive adult patients early post-LT. Cells were generated using a 2-week coculture of recipient lymphocytes with irradiated donor cells in the presence of anti-CD80/86 monoclonal antibodies. Immunosuppressive agents were tapered from 6 months, reduced every 3 months, and completely discontinued by 18 months. After the culture, the generated cells displayed cell-number-dependent donor-specific inhibition in the mixed lymphocyte reaction. Infusion of these cells caused no significant adverse events. Currently, all patients are well with normal graft function and histology. Seven patients have completed successful weaning and cessation of immunosuppressive agents. At present, they have been drug free for 16-33 months; 4 patients have been drug free for more than 24 months. The other 3 recipients with autoimmune liver diseases developed mild rejection during weaning and then resumed conventional low-dose immunotherapy. Conclusions: A cell therapy using an ex vivo-generated regulatory T-cell-enriched cell product is safe and effective for drug minimization and operational tolerance induction in living donor liver recipients with nonimmunological liver diseases. (HEPATOLOGY 2016;64:632-643) SEE EDITORIAL ON PAGE 347 E arly results after liver transplantation (LT) have been greatly improved by the evolution of potent antirejection agents. However, unfortunately, late outcomes remain unsatisfactory because of immunological and nonimmunological complications that are largely associated with lifelong immunosuppression (IS). They are infection, de novo malignancy, chronic rejection, and kidney, cardiovascular, and

Rejection is the major barrier to successful transplantation. The immune response to an allograft is an ongoing dialogue between the innate and adaptive immune system that if left unchecked will lead to the rejection of transplanted cells, tissues, or organs. Activation of elements of the innate immune system, triggered as a consequence of tissue injury sustained during cell isolation or organ retrieval and ischemia reperfusion, will initiate and amplify the adaptive response. T cells require a minimum of two signals for activation, antigen recognition, and costimulation. The activation requirements of naive T cells are more stringent than those of memory T cells. Memory T cells are present in the majority of transplant recipients as a result of heterologous immunity. The majority of B cells require help from T cells to initiate antibody production. Antibodies reactive to donor human leukocyte antigen molecules, minor histocompatibility antigens, endothelial cells, RBCs, or autoantigens can trigger or contribute to rejection early and late after transplantation. Antibody-mediated rejection triggered by alloantibody binding and complement activation is recognized increasingly as a significant contribution to graft loss. Even though one component of the immune system may dominate and lead to rejection being described in short hand as T cell or antibody mediated, it is usually multifactorial resulting from the integration of multiple mechanisms. Identifying the molecular pathways that trigger tissue injury, signal transduction and rejection facilitates the identification of targets for the development of immunosuppressive drugs.

We show for the first time the unique ability of human Tregs to prevent the rejection of a skin allograft in vivo, highlighting the therapeutic potential of these cells clinically.

Blockade of CD40-CD154 signaling pathway is an attractive strategy to induce potent immunosuppression and tolerance in organ transplantation. Due to its strong immunosuppressive effect shown in nonhuman primate experiments, anti-CD154 monoclonal antibodies (mAbs) have been tried in clinical settings, but it was interrupted by unexpected thromboembolic complications. Thus, inhibition of the counter molecule, CD40, has remained an alternative approach. In the previous preliminary study, we have shown that 4D11, a novel fully human anti-CD40 mAb, has a fairly potent immunosuppressive effect on kidney allograft in nonhuman primates. In this study, we aimed to confirm the efficacy and untoward events of the 2-week induction and 180-day maintenance 4D11 treatments. In both, 4D11 significantly suppressed T-cell-mediated alloimmune responses and prolonged allograft survival. Addition of weekly 4D11 administration after the induction treatment further enhanced graft survival. Complete inhibition of both donor-specific Ab and anti-4D11 Ab productions was obtained only with higherdose maintenance therapy. No serious side effect including thromboembolic complications was noted except for a transient reduction of hematocrit in one animal, and decrease of peripheral B-cell counts in all. These results indicate that the 4D11 appears to be a promising candidate for immunosuppression in clinical organ transplantation.

DHMEQ ameliorated experimental colitis in mice. These results indicate that DHMEQ appears to be an attractive therapeutic agent for IBD.

The engineered Fc-nonbinding (crystallizable fragment-nonbinding) CD3 antibody has lower mitogenicity and a precise therapeutic window for disease remission in patients with type 1 diabetes. Before anti-CD3 can be considered for use in transplantation, the most effective timing of treatment relative to transplantation needs to be elucidated. In this study anti-CD3F(ab′)2 fragments or saline were administered intravenously for 5 consecutive days (early: d1–3 or delayed: d3–7) to mice transplanted with a cardiac allograft (H2b-to-H2k; d0). Survival of allografts was prolonged in mice treated with the early protocol (MST = 48 days), but most were rejected by d100. In contrast, in mice treated with the delayed protocol allografts continued to survive long term. The delayed protocol significantly inhibited donor alloreactivity at d30 as compared to the early protocol. A marked increase in Foxp3+ T cells (50.3 ± 1.6%) infiltrating the allografts in mice treated with the delayed protocol was observed (p < 0.0001 vs. early (24.9 ± 2.1%)) at d10; a finding that was maintained in the accepted cardiac allografts at d100. We conclude that the timing of treatment with anti-CD3 therapy is critical for inducing long-term graft survival. Delaying administration effectively inhibits the alloreactivity and promotes the dominance of intragraft Foxp3+ T cells allowing long-term graft acceptance.

In order to obviate a small-for-size graft syndrome (SF-SGS), a portacaval (PC) shunt had been considered in a case of adult-to-adult living donor liver transplantation (AA-LDLT). In a recent AA-LDLT case, we adopted the PC shunt to resolve SFSGS; however, graft atrophy was observed in the late period of LDLT, thereby resulting in liver dysfunction. Due to the surgical closure of the PC shunt at 11 months post-LDLT, the graft regenerated gradually and resulted in the recovery of the liver function. This experience indicates that the portacaval shunt would overcome SFSGS in the early period of LDLT, while it would cause the graft atrophy and the graft dysfunction in the late period of LDLT. Adult-to-adult living donor liver transplantation (AA-LDLT) has become an established treatment option worldwide and it has been considered as an alternative to deceased donor liver transplantation due to organ shortage (1,2). From the viewpoint of the graft size mismatch, an imbalance between graft regeneration and portal hypertension can lead to progressive and severe graft dysfunction in AA-LDLT-a condition that is known as small-for-size graft syndrome (SFSGS) (3-5). In general, for a liver transplantation to be successful, the graft size should cover 30-40% of the expected liver volume for the recipient or 0.8-1.0% of the body weight (6,7). In order to resolve this problem, it has been agreed upon that a right lobe graft, which can provide sufficient graft size for the recipient, is the key to the success of AA-LDLT in the Western countries (1,3). However, the use of a right lobe graft is not always successful because there have been reports of occurrence of SFSGS in patients with the right lobe graft (8). SFSGS does not solely depend on only the graft size, but it also depends on the extent of preoperative portal hypertension in the recipient (1).The mechanism underlying this syndrome remains unclear; however, portal hypertension along with excessive portal inflow after reperfusion plays an important role in causing SFSGS by aggravating the sinusoidal microcirculatory injury to the graft (9,10). According to the clinical reports, a mesocaval shunt with downstream ligation of the superior mesenteric vein or end-to-side portacaval (PC) shunt proved useful for the SFSG (11-13). The outcome of these shunts during the early phase after liver transplantation was excellent. However, posttransplantation, there is a strong likelihood of disturbing appropriate graft regeneration with the abovementioned technique because the portal flow into the graft is not always sufficient. In a recent AA-LDLT case, we used the PC shunt to resolve SFSGS; however, due to insufficient portal inflow graft atrophy occurred in the late period of LDLT, which resulted in liver dysfunction. We introduce this case of AA-LDLT in whom the PC shunt was used. Case ReportA 44-year-old man weighing 69.6 kg underwent LDLT for subacute fulminant hepatitis B. A right lobe graft without the middle hepatic vein (MHV) was transplanted from his sister. The graft weig...

T regulatory cells (Treg) play an important role in the induction and maintenance of immunological tolerance. Recent findings in experimental transplant models combined with the development of functional reporter mice have opened new avenues to study Treg biology and their therapeutic potential. In particular, recent advances in understanding Treg function and lineage stability revealed unexpected plasticity of this lineage. Nevertheless, pre-clinical and pilot clinical trials using Treg cells as cellular therapies have been initiated suggesting the safety and feasibility of such treatment.