RESUMEN
Several approaches successfully achieve allograft tolerance in preclinical models but are challenging to translate into clinical practice. Many clinically relevant factors can attenuate allograft tolerance induction, including intrinsic genetic resistance, peritransplant infection, inflammation, and preexisting antidonor immunity. The prevailing view for immune memory as a tolerance barrier is that the host harbors memory cells that spontaneously cross-react to donor MHC antigens. Such preexisting "heterologous" memory cells have direct reactivity to donor cells and resist most tolerance regimens. In this study, we developed a model system to determine if an alternative form of immune memory could also block tolerance. We posited that host memory T cells could potentially respond to donor-derived non-MHC antigens, such as latent viral antigens or autoantigens, to which the host is immune. Results show that immunity to a model nonself antigen, ovalbumin (OVA), can dramatically disrupt tolerance despite undetectable initial reactivity to donor MHC antigens. Importantly, this blockade of tolerance was CD8+ T cell-dependent and required linked antigen presentation of alloantigens with the test OVA antigen. As such, this pathway represents an unapparent, or "incognito," form of immunity that is sufficient to prevent tolerance and that can be an unforeseen additional immune barrier to clinical transplant tolerance.
Asunto(s)
Presentación de Antígeno/inmunología , Linfocitos T CD8-positivos/inmunología , Rechazo de Injerto/inmunología , Memoria Inmunológica/inmunología , Trasplante de Islotes Pancreáticos/métodos , Tolerancia al Trasplante/inmunología , Animales , Femenino , Activación de Linfocitos , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ovalbúmina/administración & dosificación , Trasplante HomólogoRESUMEN
Systemic administration of autologous regulatory dendritic cells (DCreg; unpulsed or pulsed with donor antigen [Ag]), prolongs allograft survival and promotes transplant tolerance in rodents. Here, we demonstrate that nonhuman primate (NHP) monocyte-derived DCreg preloaded with cell membrane vesicles from allogeneic peripheral blood mononuclear cells induce T cell hyporesponsiveness to donor alloantigen (alloAg) in vitro. These donor alloAg-pulsed autologous DCreg (1.4-3.6 × 106 /kg) were administered intravenously, 1 day before MHC-mismatched renal transplantation to rhesus monkeys treated with costimulation blockade (cytotoxic T lymphocyte Ag 4 immunoglobulin [CTLA4] Ig) and tapered rapamycin. Prolongation of graft median survival time from 39.5 days (no DCreg infusion; n = 6 historical controls) and 29 days with control unpulsed DCreg (n = 2), to 56 days with donor Ag-pulsed DCreg (n = 5) was associated with evidence of modulated host CD4+ and CD8+ T cell responses to donor Ag and attenuation of systemic IL-17 production. Circulating anti-donor antibody (Ab) was not detected until CTLA4 Ig withdrawal. One monkey treated with donor Ag-pulsed DCreg rejected its graft in association with progressively elevated anti-donor Ab, 525 days posttransplant (160 days after withdrawal of immunosuppression). These findings indicate a modest but not statistically significant beneficial effect of donor Ag-pulsed autologous DCreg infusion on NHP graft survival when administered with a minimal immunosuppressive drug regimen.
Asunto(s)
Células Dendríticas/inmunología , Supervivencia de Injerto/inmunología , Isoantígenos/inmunología , Fallo Renal Crónico/cirugía , Trasplante de Riñón , Linfocitos T/inmunología , Donantes de Tejidos , Animales , Leucocitos Mononucleares , Macaca mulatta , Masculino , Tolerancia al Trasplante , Trasplante HomólogoRESUMEN
Transforming growth factor ß1 (TGFß1) plays a key role in T cell homeostasis and peripheral tolerance. We evaluated the influence of a novel human mutant TGFß1/Fc (human IgG4 Fc) fusion protein on memory CD4+ and CD8+ T cell (Tmem) responses in vitro and their recovery following antithymocyte globulin (ATG)-mediated lymphodepletion in monkeys. TGFß1/Fc induced Smad2/3 protein phosphorylation in rhesus and human peripheral blood mononuclear cells and augmented the suppressive effect of rapamycin on rhesus Tmem proliferation after either alloactivation or anti-CD3/CD28 stimulation. In combination with IL-2, the incidence of CD4+ CD25hi Foxp3hi regulatory T cells (Treg) and Treg:Th17 ratios were increased. In lymphodepleted monkeys, whole blood trough levels of infused TGFß1/Fc were maintained between 2 and 7 µg/mL for 35 days. Following ATG administration, total T cell numbers were reduced markedly. In those given TGFß1/Fc infusion, CD8+ T cell recovery to predepletion levels was delayed compared to controls. Additionally, numbers of CD4+ CD25hi CD127lo Treg increased at 4-6 weeks after depletion but subsequently declined to predepletion levels by 12 weeks. In all monkeys, CD4+ CD25hi Foxp3hi Treg/CD4+ IL-17+ cell ratios were reduced, particularly after stopping TGFß1/Fc infusion. Thus, human TGFß1/Fc infusion may delay Tmem recovery following lymphodepletion in nonhuman primates. Combined (low-dose) IL-2 infusion may be required to improve the Treg:Th17 ratio following lymphodepletion.
Asunto(s)
Homeostasis/inmunología , Memoria Inmunológica/inmunología , Depleción Linfocítica/efectos adversos , Receptores Fc/metabolismo , Linfocitos T Reguladores/inmunología , Factor de Crecimiento Transformador beta1/metabolismo , Animales , Humanos , Leucocitos Mononucleares/inmunología , Macaca mulatta , Masculino , Receptores Fc/genética , Factor de Crecimiento Transformador beta1/genéticaRESUMEN
The ability of regulatory T cells (Treg) to prolong allograft survival and promote transplant tolerance in lymphodepleted rodents is well established. Few studies, however, have addressed the therapeutic potential of adoptively transferred, CD4(+) CD25(+) CD127(-) Foxp3(+) (Treg) in clinically relevant large animal models. We infused ex vivo-expanded, functionally stable, nonselected Treg (up to a maximum cumulative dose of 1.87 billion cells) into antithymocyte globulin-lymphodepleted, MHC-mismatched cynomolgus monkey heart graft recipients before homeostatic recovery of effector T cells. The monkeys also received tacrolimus, anti-interleukin-6 receptor monoclonal antibodies and tapered rapamycin maintenance therapy. Treg administration in single or multiple doses during the early postsurgical period (up to 1 month posttransplantation), when host T cells were profoundly depleted, resulted in inferior graft function compared with controls. This was accompanied by increased incidences of effector memory T cells, enhanced interferon-γ production by host CD8(+) T cells, elevated levels of proinflammatory cytokines, and antidonor alloantibodies. The findings caution against infusion of Treg during the early posttransplantation period after lymphodepletion. Despite marked but transient increases in Treg relative to endogenous effector T cells and use of reputed "Treg-friendly" agents, the host environment/immune effector mechanisms instigated under these conditions can perturb rather than favor the potential therapeutic efficacy of adoptively transferred Treg.
Asunto(s)
Linfocitos T CD8-positivos/inmunología , Rechazo de Injerto/inmunología , Trasplante de Corazón , Memoria Inmunológica/inmunología , Isoanticuerpos/inmunología , Linfocitos T Reguladores/inmunología , Tolerancia al Trasplante/inmunología , Traslado Adoptivo , Aloinjertos , Animales , Supervivencia de Injerto , Depleción Linfocítica , Macaca fascicularisRESUMEN
Ex vivo-expanded cynomolgus monkey CD4(+)CD25(+)CD127(-) regulatory T cells (Treg) maintained Foxp3 demethylation status at the Treg-specific demethylation region, and potently suppressed T cell proliferation through three rounds of expansion. When carboxyfluorescein succinimidyl ester- or violet proliferation dye 450-labeled autologous (auto) and nonautologous (non-auto)-expanded Treg were infused into monkeys, the number of labeled auto-Treg in peripheral blood declined rapidly during the first week, but persisted at low levels in both normal and anti-thymocyte globulin plus rapamycin-treated (immunosuppressed; IS) animals for at least 3 weeks. By contrast, MHC-mismatched non-auto-Treg could not be detected in normal monkey blood or in blood of two out of the three IS monkeys by day 6 postinfusion. They were also more difficult to detect than auto-Treg in peripheral lymphoid tissue. Both auto- and non-auto-Treg maintained Ki67 expression early after infusion. Sequential monitoring revealed that adoptively transferred auto-Treg maintained similarly high levels of Foxp3 and CD25 and low CD127 compared with endogenous Treg, although Foxp3 staining diminished over time in these nontransplanted recipients. Thus, infused ex vivo-expanded auto-Treg persist longer than MHC-mismatched non-auto-Treg in blood of nonhuman primates and can be detected in secondary lymphoid tissue. Host lymphodepletion and rapamycin administration did not consistently prolong the persistence of non-auto-Treg in these sites.