Interleukin-12 (IL-12)-driven alloimmune responses in vitro and in vivo: requirement for beta1 subunit of the IL-12 receptor

Transforming growth factor-beta 1 delivery from microporous scaffolds decreases inflammation post-implant and enhances function of transplanted islets

Biomaterial scaffolds are central to many regenerative strategies as they create a space for infiltration of host tissue and provide a platform to deliver growth factors and progenitor cells. However, biomaterial implantation results in an unavoidable inflammatory response, which can impair tissue regeneration and promote loss or dysfunction of transplanted cells. We investigated localized TGF-β1 delivery to modulate this immunological environment around scaffolds and transplanted cells. TGF-β1 was delivered from layered scaffolds, with protein entrapped within an inner layer and outer layers designed for cell seeding and host tissue integration. Scaffolds were implanted into the epididymal fat pad, a site frequently used for cell transplantation. Expression of cytokines TNF-α, IL-12, and MCP-1 were decreased by at least 40% for scaffolds releasing TGF-β1 relative to control scaffolds. This decrease in inflammatory cytokine production corresponded to a 60% decrease in leukocyte infiltration. Transplantation of islets into diabetic mice on TGF-β1 scaffolds significantly improved the ability of syngeneic islets to control blood glucose levels within the first week of transplant and delayed rejection of allogeneic islets. Together, these studies emphasize the ability of localized TGF-β1 delivery to modulate the immune response to biomaterial implants and enhance cell function in cell-based therapies.

Francisella tularensis LVS-induced Interleukin-12 p40 cytokine production mediates dendritic cell migration through IL-12 Receptor β1

Three cytokines use the IL-12p40 cytokine subunit namely: IL-12p70 (IL-12-comprised of IL-12p40 and IL-12p35), IL-23 (comprised of the IL-12p40 and IL-23p19 subunits) and homodimeric IL-12p40 (IL-12(p40)(2)). Following activation, immature dendritic cells (DCs) upregulate the chemokine receptor Chemokine-C-Receptor 7 (CCR7), and migrate in response to homeostatic chemokines such as chemokine (C-C motif) ligand 19 (CCL19). Induction of the cytokine IL-12p40 in response to pathogen-exposure, likely in its homodimeric form, is one of the primary events that mediates migration of DCs in response to CCL19. Here we show that following exposure to Francisella tularensis Live Vaccine Strain (LVS), DCs produce IL-12p40 and promote the migration of DCs to the chemokine CCL19 in an IL-12Rβ1- and IL-12p(40)(2)-dependent manner. Induction of IL-12p40 and resulting chemokine responsiveness in DCs is TLR2-dependent and coincides with the uptake of F. tularensis LVS and activation of DCs. Importantly, we show that IL-12Rβ1 signaling is required for DC migration from the lung to the draining lymph node following F. tularensis LVS exposure and coincides with accumulation of IL-12p40 expressing DCs in the draining lymph nodes. Together, these findings illustrate that IL-12p40 is induced rapidly in response to F. tularensis LVS and is required for DC migration through an IL-12Rβ1-IL-12(p40)(2) dependent mechanism.

Coupled regulation of interleukin-12 receptor beta-1 of CD8+ central memory and CCR7-negative memory T cells in an early alloimmunity in liver transplant recipients

This study investigated how CD8(+) T cell subsets respond to allo- and infectious immunity after living donor liver transplantation (LDLT). Early alloimmunity: 56 recipients were classified into three types according to the post-transplant course; type I demonstrated uneventful post-transplant course, type II developed severe sepsis leading to multiple organ dysfunction syndrome or retransplantation and type III with acute rejection. In 23 type I recipients, the interleukin (IL)-12 receptor beta-1 (R beta 1)(+) cells of central memory T cells (Il-12R beta 1(+) T(CM)) were increased above the pretransplant level. In 16 type II recipients, IL-12R beta 1(+) T(CM) was decreased markedly below the pretransplant level on postoperative day (POD) 5. In 17 type III recipients, IL-12R beta 1(+) T(CM) was decreased for a more prolonged period until POD 10. Along with down-regulation of IL-12R beta 1(+) T(CM), the IL-12R beta 1(+) cells of CCR7-negative subsets (CNS) as well as perforin, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha decreased gradually, resulting in the down-regulation of effectors and cytotoxicity. The down-regulation of IL-12R beta 1(+) T(CM) was suggested to be due to the recruitment of alloantigen-primed T cells into the graft, and then their entry into the secondary lymphoid organ, resulting in graft destruction. Infectious immunity: immunocompetent memory T cells with the capacity to enhance effectors and cytotoxicity were generated in response to post-transplant infection along with both up-regulation of the IL-12R beta 1(+) T(CM) and an increase in the CNS showing the highest level of IL-12R beta 1(+) cells. In conclusion, this work demonstrated that the IL-12R beta 1(+) cells of T(CM) and CNS are regulated in a tightly coupled manner and that expression levels of IL-12R beta 1(+) T(CM) play a crucial role in controlling allo- and infectious immunity.

Interleukin-17 is required for T helper 1 cell immunity and host resistance to the intracellular pathogen Francisella tularensis

The importance of T helper type 1 (Th1) cell immunity in host resistance to the intracellular bacterium Francisella tularensis is well established. However, the relative roles of interleukin (IL)-12-Th1 and IL-23-Th17 cell responses in immunity to F. tularensis have not been studied. The IL-23-Th17 cell pathway is critical for protective immunity against extracellular bacterial infections. In contrast, the IL-23-Th17 cell pathway is dispensable for protection against intracellular pathogens such as Mycobacteria. Here we show that the IL-23-Th17 pathway regulates the IL-12-Th1 cell pathway and was required for protective immunity against F.tularensis live vaccine strain. We show that IL-17A, but not IL-17F or IL-22, induced IL-12 production in dendritic cells and mediated Th1 responses. Furthermore, we show that IL-17A also induced IL-12 and interferon-gamma production in macrophages and mediated bacterial killing. Together, these findings illustrate a biological function for IL-17A in regulating IL-12-Th1 cell immunity and host responses to an intracellular pathogen.

Initial steroid bolus injection promotes vigorous CD8+ alloreactive responses toward early graft acceptance immediately after liver transplantation in humans

We have found that steroid bolus withdrawal prior to graft reperfusion increased the incidence of acute cellular rejection (ACR). This study aims to clarify how initial steroid bolus (ISB) injection at reperfusion influences the kinetics of CD8(+) alloreactive immune responses immediately after living donor liver transplantation (LDLT). A total of 49 hepatitis C virus (HCV)-infected recipients were classified into 3 groups according to hierarchical clustering by preoperative CD8(+)CD45 isoforms. The naive T cell proportion was considerably higher in Group I than in Groups II and III, whereas Group II recipients had the highest effector memory (EM) T cells and Group III the highest effector T cells. The frequency of ACR was significantly higher in recipients without ISB than in those with ISB. In particular, the ACR rates were the highest in Group II without ISB. Following ISB, the proportion of effector T cells was promptly upregulated within 6 hours after graft reperfusion, simultaneously with the upregulation of CD27(-)CD28(-) subsets, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha and perforin expression, which significantly correlated with increasing interleukin (IL)-12 receptor beta 1 cells. These were then downregulated to below preoperative levels by tacrolimus (Tac) administered at 24 hours. These changes did not occur in the absence of ISB. In Group II without ISB, the downregulation of IL-12Rbeta1(+) cells was the greatest, consistent with the highest rates of ACR and mortality (60%). In conclusion, ISB must be done in place, especially in Group II with preexisting high EM T cells, to enable the development of early allograft acceptance.

Interleukin-12p70 Prolongs Allograft Survival by Induction of Interferon Gamma and Nitric Oxide Production

BACKGROUND

Interleukin (IL)-12p70, a heterodimeric cytokine has been considered central to induction of Th1 responses with the assistance of IL-18 and IL-27. It was predicted IL-12p70 treatment would promote allograft rejection. In these studies, IL-12p70 delayed rejection.

METHODS

We compared Piebald Virol Glaxo (PVG) neonatal heart graft survival in fully allogeneic Dark Agoutti (DA) rats treated with IL-12p70 alone or in combination with other cytokines. The mechanism by which IL-12p70 induced delayed rejection was examined by reverse transcription polymerase chain reaction of cytokine mRNA and studying the role of interferon (IFN)-gamma and inducible nitric oxide synthase (iNOS) that were induced by IL-12.

RESULTS

IL-12p70 treatment significantly delayed PVG neonatal heart graft rejection compared to normal rejection control and other control groups treated with supernatant from Chinese hamster ovary (CHO)-K1 cells transfected with IL-12p35, IL-12p40, or no cytokine gene. IL-12p70 had no effect on alloantibody response. IFN-gamma and iNOS mRNA expression was increased in heart graft and regional lymph node compared to normal rejection and other treatment groups, consistent with Th1 response induction. IL-12p35 mRNA expression decreased in IL-12p70 treated rats but there was no difference in IL-12p40, Th2, or Tr1 cytokine mRNA expression. Coadministration of an iNOS inhibitor, L-NIL, or a monoclonal antibody (mAb) that blocks IFN-gamma, inhibited IL-12p70's ability to prolong allograft survival; as did co-treatment with IL-4 but not IL-13.

CONCLUSIONS

IL-12p70 treatment may inhibit rejection by hyperinduction of Th1 responses, especially production of IFN-gamma and nitric oxide. These effects may be by enhancing regulatory T-cell responses or by the activation of iNOS in macrophages to produce excessive nitric oxide that in turn inhibits alloimmune responses.

Differential effects of IL-12 on the generation of alloreactive CTL mediated by murine and human dendritic cells: a critical role for nitric oxide

We examined the mechanisms involved in interleukin (IL)-12-mediated suppression of cellular immunity in mice using allogeneic mixed leukocyte reaction (MLR) stimulated by dendritic cells (DCs) in vitro and compared the effect of IL-12 on MLR in mice and humans. Although IL-12 stimulated human MLR, the addition of IL-12 or interferon-gamma (IFN-gamma) resulted in a dose-dependent suppression of MLR in mice. The treatment with N(G)-monomethyl-L-arginine (L-NMMA) completely abrogated IL-12- and IFN-gamma-mediated suppression of MLR in mice. Furthermore, IL-12 enhanced the alloreactive cytolytic T lymphocyte (CTL) induction in human MLR, whereas the addition of L-NMMA was required to generate alloreactive CTLs in the presence of IL-12 in mice. Nitric oxide (NO) was detected only in mouse MLR. Murine DCs could produce NO, but neither human CD34(+) cell- nor monocyte-derived DCs produced a detectable amount of NO. These results suggest that NO produced by DCs might play an important role in IL-12-mediated immune suppression in mice but not in humans.

Mice lacking bioactive IL-12 can generate protective, antigen-specific cellular responses to mycobacterial infection only if the IL-12 p40 subunit is present

Recent evidence suggests that absence of the IL-12p40 subunit is more detrimental to the generation of protective responses than is the absence of the p35 subunit. To determine whether this is the case in tuberculosis, both p35 and p40 knockout mice were infected with Mycobacterium tuberculosis. Mice lacking the p40 subunit were highly susceptible to increased bacterial growth, exhibited reduced production of IFN-gamma, and had increased mortality. In contrast, mice lacking the p35 subunit exhibited a moderate ability to control bacterial growth, were able to generate Ag-specific IFN-gamma responses, and survived infection longer. The superior Ag-specific responses of the p35 gene-disrupted mice, when compared with the p40 gene-disrupted mice, suggest that the p40 subunit may act other than as a component of IL-12. A candidate molecule capable of driving the protective responses in the p35 gene-disrupted mice is the novel cytokine IL-23. This cytokine is composed of the IL-12 p40 subunit and a p19 subunit. In support of a role for this cytokine in protective responses to M. tuberculosis, we determined that the p19 subunit is induced in the lungs of infected mice.

DNA-liposome versus adenoviral mediated gene transfer of transforming growth factor beta1 in vascularized cardiac allografts: differential sensitivity of CD4+ and CD8+ T cells to transforming growth factor beta1

We have developed a model of transforming growth factor (TGF)beta1 gene transfer into mouse vascularized cardiac allografts to study the use of gene transfer as an immunosuppressive therapy in transplantation. Donor hearts were perfused with either DNA-liposome complexes or adenoviral vectors that encode the active form of human TGFbeta1. DNA-liposome mediated transfection prolonged allograft survival in approximately two-thirds of transplant recipients, while adenoviral delivery of TGFbeta1 was not protective. Protective TGFbeta1 gene transfer was associated with reduced Th1 responses and an inhibition of the alloantibody isotype switch. The protective effects of TGFbeta1 gene transfer were overridden by exogenous interleukin-12 administration. Interestingly, alloreactive CD4+ and CD8+ cells exhibited distinct sensitivities to TGFbeta1 gene transfer: CD4+ Th1 function was abrogated by this modality, although CD8+ Th1 function was not. Transient depletion of recipient CD8+ cells markedly prolonged the survival of grafts transfected with either DNA-liposome complexes or adenoviral vectors. Transgene expression persisted for at least 60 days, and Th1 responses were not detectable until CD8+ T cells repopulated the periphery. However, long-term transfected allografts appeared to exhibit exacerbated fibrosis and neointimal development. These manifestations of chronic rejection were absent in long-term transfected isografts, suggesting that long-term expression of active TGFbeta1 alone is not sufficient to induce fibrosis of the grafts. Collectively, these data illustrate the utility of immunosuppressive gene therapy as a treatment for transplantation when combined with additional conditioning regimens. Further, they illustrate that alloreactive CD4+ and CD8+ cells may be differentially influenced by cytokine manipulation strategies.

Interleukin-12. Opportunities for the treatment of bladder cancer

Despite incomplete understanding of the human immune system, the rapid progress in tumor immunology provides a framework for more effective and safe interventions in the near future. Early approaches in patients with cancer that have focused on the nonspecific and broad stimulation of the immune system by interferons and IL-12 will be replaced by the highly specific stimulation of immune reactions targeting precisely defined tumor antigens. IL-12 has several biologic properties that seem useful in immune therapy for bladder cancer. The striking antitumor responses with IL-12 in preclinical animal models of bladder cancer provide optimism that future clinical trials involving this agent may impact on the risk and mortality associated with this disease.

Chemokines and cytokines in inflammatory bowel disease and their application to disease treatment

The term inflammatory bowel disease refers to two chronic, relapsing or remitting, inflammatory disorders of the intestinal tract that although somewhat similar clinically represent two markedly different and distinct disorders histologically, endoscopically, immunologically, and by many other means. The pathogenesis of these diseases, ulcerative colitis and Crohn's disease, remains unknown and medical and surgical therapy is limited. Approximately 70% of individuals with Crohn's disease require surgery with another 40% to 45% requiring reoperation, whereas approximately 20% to 25% of patients with ulcerative colitis undergo surgical intervention. This review highlights the specific clinical features of the disease as well as some of the recent insights into the cause of the disease. Standard medical therapy is highlighted and more recent biologic therapies including the use of anti-tumor necrosis factor-alpha antibodies are described. The changing focus of therapy from nonspecific anti-inflammatory medications to targeted biologic therapies is reviewed. A number of novel therapeutic targets are highlighted and future directions for research and clinical testing are discussed.