Simultaneous blockade of the CD40 and CD28 costimulatory pathways is an effective treatment strategy to promote allograft acceptance but does not lead to indefinite allograft survival. The immune mechanisms responsible for costimulation-independent rejection are not defined. Here we have studied the rejection responses of murine C57BL/6 recipients, which we show to be relatively resistant to inhibition by combined CD40/CD28 blockade. We demonstrate that asialo GM1 + CD8 + cells play a critical role in this costimulation blockade-resistant rejection. These results provide new insights into the costimulatory requirements for T-cell subsets and demonstrate for the first time that combined blockade of the CD40 and CD28 pathways does not adequately inhibit CD8-mediated skin allograft rejection. Furthermore, we provide evidence that asialo GM1 is a potentially important therapeutic target for CD8-dependent immune responses.

Mixed hemopoietic chimerism has the potential to correct genetic hemological diseases (sickle cell anemia, thalassemia) and eliminate chronic immunosuppressive therapy following organ transplantation. To date, most strategies require either recipient conditioning (γ-irradiation, depletion of the peripheral immune system) or administration of “mega” doses of bone marrow to facilitate reliable engraftment. Although encouraging, many issues remain that may restrict or prevent clinical application of such strategies. We describe an alternative, nonirradiation based strategy using a single dose of busulfan, costimulation blockade, and T cell-depleted donor bone marrow, which promotes titratable macrochimerism and a reshaping of the T cell repertoire. Chimeras exhibit robust donor-specific tolerance, evidenced by acceptance of fully allogeneic skin grafts and failure to generate donor-specific proliferative responses in an in vivo graft-versus-host disease model of alloreactivity. In this model, donor cell infusion and costimulation blockade without busulfan were insufficient for tolerance induction as donor-specific IFN-γ-producing T cells re-emerged and skin grafts were rejected at ∼100 days. When applied to a murine β-thalassemia model, this approach allows for the normalization of hemologic parameters and replacement of the diseased red cell compartment. Such a protocol may allow for clinical application of mixed chimerism strategies in patients with end-stage organ disease or hemoglobinopathies.

Transplantation tolerance, defined as allograft acceptance by an immunocompetent recipient in the absence of long-term immunosuppression, has remained an elusive goal in clinical transplantation. Robust experimental tolerance induction strategies have in common methods to induce mixed hemopoietic chimerism. To date, however, chimerism induction across allogeneic barriers has required recipient conditioning with irradiation or cytoablative agents. In this paper we show that B6 recipients of fully allogeneic BALB/c skin grafts treated with repeated doses of donor bone marrow and anti-CD40 ligand (CD40L) develop durable (>300 days), readily detectable (6-12%) multilineage hemopoietic chimerism, indefinite allograft acceptance (>300 days), and donor-specific tolerance to secondary skin grafts. Analysis of the TCR repertoire of treated mice indicates that the underlying mechanisms of tolerance are in part mediated by deletion of donor-reactive T cells. These data demonstrate that durable hemopoietic chimerism and robust transplantation tolerance can be achieved without cytotoxic conditioning using a potentially clinically applicable regimen.

Pig islets are an alternative source for islet transplantation to treat type 1 diabetes (T1D), but reproducible curative potential in the pig-to-nonhuman primate (NHP) model has not been demonstrated. Here, we report that pig islet grafts survived and maintained normoglycemia for >6 months in four of five consecutive immunosuppressed NHPs. Pig islets were isolated from designated pathogen-free (DPF) miniature pigs and infused intraportally into streptozotocin-induced diabetic rhesus monkeys under pretreatment with cobra venom factor (CVF), anti-thymocyte globulin (ATG) induction and maintenance with anti-CD154 monoclonal antibody and low-dose sirolimus. Ex vivo expanded autologous regulatory T cells were adoptively transferred in three recipients. Blood glucose levels were promptly normalized in all five monkeys and normoglycemia (90-110 mg/dL) was maintained for >6 months in four cases, the longest currently up to 603 days. Intravenous glucose tolerance tests during the follow-up period showed excellent glucose disposal capacity and porcine C-peptide responses. Adoptive transfer of autologous regulatory T cells was likely to be associated with more stable and durable normoglycemia. Importantly, the recipients showed no serious adverse effects. Taken together, our results confirm the clinical feasibility of pig islet transplantation to treat T1D patients without the need for excessive immunosuppressive therapy.

The IIV of tacrolimus trough concentrations had a significant impact on rejection-free survival. The effect was influenced by CYP3A5 polymorphism, although the tacrolimus variability itself was not determined by the CYP3A5 polymorphism.

Simultaneous blockade of the CD40 and CD28 T cell costimulatory pathways effectively promotes skin allograft survival in C3H/HeJ mice, extending median survival times (MSTs) beyond 100 days. This strategy is markedly less effective in C57BL/6 mice, with MSTs ranging between 20 and 30 days. In this study, we investigate the underlying genetic causes of these distinct phenotypes. Using H-2 congenic mice, we show that the genetic basis for the varied responses between these two strains is independent of the H-2 locus and T cell precursor frequency. C57BL/6 mice treated with costimulation blockade are able to generate allospecific CTL- and IFN-γ-producing T cells within 3–4 wk posttransplant, whereas mice with a C3H background generate neither CTL- nor IFN-γ-producing cells. Thus, differences appear to be in the generation of the immune response and not T cell homing. Strain differences in costimulation blockade-induced hyporesponsiveness persist in the absence of CD4+ T cells, implying a direct effect on CD8+ T cells. We demonstrate that genetic differences are important in cells of hemopoietic origin and that the costimulation blockade-resistant phenotype is dominant. Analysis of BXH recombinant inbred strains indicates that multiple loci contribute to the phenotype, and that the blockade resistance loci are preliminarily linked to 17 markers on four chromosomes. We conclude that strain variation in allograft MSTs following CD40/CD28 blockade results from the ability of CD8+ T cells in some strains to use alternative modes of costimulation to mount an effective alloresponse.

Tolerance to self is a necessary attribute of the immune system. It is thought that most autoreactive T cells are deleted in the thymus during the process of negative selection. However, peripheral tolerance mechanisms also exist to prevent development of autoimmune diseases against peripheral self-Ags. It has been proposed that T cells develop tolerance to peripheral self-Ags encountered in the absence of inflammation or “danger” signals. We have used immunodeficient Rag 1−/− mice to study the response of T cells to neo-self peripheral Ags in the form of well-healed skin and vascularized cardiac allografts. In this paper we report that skin and cardiac allografts without evidence of inflammation are vigorously rejected by transferred T cells or when recipients are reconstituted with T cells at a physiologic rate by nude bone graft transplantation. These results provide new insights into the role of inflammation or “danger” in the initiation of T cell-dependent immune responses. These findings also have profound implications in organ transplantation and suggest that in the absence of central deletional tolerance, peripheral tolerance mechanisms are not sufficient to inhibit alloimmune responses even in the absence of inflammation or danger.

BackgroundNonadherence to immunosuppressive therapy after renal transplantation is associated with poor graft outcomes. We aimed to evaluate whether the use of the Adhere4U mobile medication manager application could improve adherence among renal transplant recipients ≥1 year posttransplantation. Adhere4U can provide medication reminders, monitor medication use, and provide information on immunosuppressants.MethodsWe conducted a prospective randomized controlled study to compare the rate of nonadherence to index immunosuppressant (tacrolimus or cyclosporine) in a group using the Adhere4U app (mobile group) and in another group receiving conventional care (control group). The primary outcome was the nonadherence rate, which was evaluated using an electronic medication event monitoring system during the 6-month intervention period. Our secondary outcome included self-reported adherence using the Basel Assessment of Adherence to Immunosuppressive Medication Scale (BAASIS) and the visual analog scale (VAS) based on a 4-week recall on days 28, 90, and 180. Longitudinal data of repeated measures of self-rated adherence were analyzed using generalized estimating equations (GEE) to compare the between-group difference in adherence change over time.ResultsBetween November 2013 and May 2015, 138 renal transplant recipients were randomly allocated to the control (n = 67) or the mobile group (n = 71). The overall nonadherence rate over the 6-month study period by electronic monitoring was 63.6%, with no between-group difference [mobile group, 65.0% (n = 39/60); control group, 62.1% (n = 36/58); odds ratio 1.14; 95% confidence interval 0.53–2.40; p = 0.89]. Self-rated nonadherence assessed using the BAASIS and VAS at baseline was 53.7% and 51.5%, respectively. Although the self-rated nonadherence by BAASIS of the mobile group was lower than the control group throughout the study period, there was no between-group difference in the change of nonadherence over time (χ2 = 2.82, df = 3, p = 0.42 by logistic GEE). There also was no significant between-group difference in the nonadherence by VAS (χ2 = 1.71, df = 3, p = 0.63 by logistic GEE) over time. The main limitation of this study was the low rate of patient engagement with the app among the mobile group. The rate of app use was 47.6% (31/65) at 28 days, 33.9% (19/56) at 90 days, and 11.5% (6/52) at 180 days.ConclusionsThe Adhere4U application did not improve adherence to immunosuppressive therapy. Our evidence is limited by the high rate of attrition. Further studies on strategies to facilitate patient engagement with mobile interventions are warranted.