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Reshaping the immune balance by adoptive transfer of regulatory T-cells (Tregs) has emerged as a promising strategy to combat undesired immune reactions, including in Graft-versus-Host Disease (GvHD), which is the most lethal non-relapse complication of allogeneic hematopoietic stem cell transplantation. Currently however, little is known about the potentially inhibitory in vivo effects of conventional immunosuppressive drugs, which are routinely used to treat GvHD, on adoptively transferred Tregs. Here we demonstrate drug-specific effects of the conventional immunosuppressive drugs Cyclosporine A, Mycophenolate mofetil and methylprednisolone on adoptively transferred Tregs in a humanized NOD/SCID/IL2Rgamma-/- GvHD mouse model. The clinical course of GvHD and postmortem organ histology, including cellular organ infiltration, showed that co-administration of Cyclosporine A and Tregs is highly beneficial as it enhanced Treg accumulation at inflammatory sites like lung and liver. Similarly, co-administration of Mycophenolate mofetil and Tregs improved clinical signs of GvHD. In contrast, co-administration of methylprednisolone and Tregs resulted in reduced Treg recruitment to inflammatory sites and the fast deterioration of some animals. Consequently, when clinical trials investigating safety and efficacy of adjunctive Treg therapy in GvHD are designed, we suggest co-administering Cyclosporine A, whereas high doses of glucocorticosteroids should be avoided., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Landwehr-Kenzel, Zobel, Schmitt-Knosalla, Forke, Hoffmann, Schmueck-Henneresse, Klopfleisch, Volk and Reinke.)

Purpose: To analyze the immune modulatory effect of low-dose systemic treatment with rapamycin (Rapa) alone or in combination with cyclosporin A (CsA) in a high-responder corneal allograft model., Methods: A total of 80 C57BL/6 mice received corneal grafts from BALB/c donors. Recipients were treated with either CsA 3 mg/kg/day or Rapa 0.5 mg/kg/day monotherapy or received combined treatment. Immunomodulatory treatment was started on the day of surgery, and continued for 14 days. The frequency of CD4(+)CD25(+)Foxp3(+) T regulatory cells (Treg) in secondary lymphoid organs was measured by flow cytometry. Development of IFN-gamma producing alloreactive T cells was estimated by Elispot. In addition, corneal samples were subjected to real-time RT-PCR analysis for cytokine transcription., Results: Monotherapy with Rapa significantly delayed allograft rejection (13.4 +/- 1.34 days, p = 0.03). However, the combination of both, low-dose Rapa and CsA prolonged corneal allograft survival at a significantly higher level (MST = 17.1 +/- 1.37 days, p = 0.0001) than in the control group (MST = 11.2 +/- 1.91 days). Rapa monotherapy increased the frequency of CD4(+)CD25(+)Foxp3(+)Treg in draining lymph nodes, whereas addition of CsA reduced Tregs. Monotherapy with Rapa as well as combined treatment prevented development of IFN-gamma producing alloreactive T cells in spleen. Combined treatment resulted in down-regulation of intragraft CD3, IL-2, IFN-gamma and IL-10 transcription (p = 0.028, p = 0.027, p = 0.028 and p = 0.027 respectively)., Conclusions: Combined treatment with low-dose CsA and Rapa resulted in superior graft survival, and effectively modulated mRNA expression of inflammation and infiltration markers.

Human natural killer (NK) cells comprise 2 main subsets, CD56(bright) and CD56(dim) cells, that differ in function, phenotype, and tissue localization. To further dissect the heterogeneity of CD56(dim) cells, we have performed transcriptome analysis and functional ex vivo characterization of human NK-cell subsets according to the expression of markers related to differentiation, migration or competence. Here, we show for the first time that the ability to respond to cytokines or to activating receptors is mutually exclusive in almost all NK cells with the exception of CD56(dim) CD62L(+) cells. Indeed, only these cells combine the ability to produce interferon-gamma after cytokines and proliferate in vivo during viral infection with the capacity to kill and produce cytokines upon engagement of activating receptors. Therefore, CD56(dim) CD62L(+) cells represent a unique subset of polyfunctional NK cells. Ex vivo analysis of their function, phenotype, telomere length, frequencies during ageing as well as transfer experiments of NK-cell subsets into immunodeficient mice suggest that CD56(dim) CD62L(+) cells represent an intermediate stage of NK-cell maturation, which after restimulation can accomplish multiple tasks and further develop into terminally differentiated effectors.

T-bet plays a crucial role in Th1 development. We investigated the role of T-bet in the development of allograft rejection in an established MHC class II-mismatched (bm12 into B6) model of chronic allograft vasculopathy (CAV). Intriguingly, and in contrast to IFN-gamma(-/-) mice that are protected from CAV, T-bet(-/-) recipients develop markedly accelerated allograft rejection accompanied by early severe vascular inflammation and vasculopathy, and infiltration by predominantly IL-17-producing CD4 T cells. Concurrently, T-bet(-/-) mice exhibit a T helper type 1 (Th1)-deficient environment characterized by profound IFN-gamma deficiency, a Th2 switch characterized by increased production of interleukin (IL) 4, IL-5, IL-10, and IL-13 cytokines, as well as increased production of the proinflammatory cytokines IL-6, IL-12p40, and IL-17. Neutralization of IL-17 inhibits accelerated allograft rejection and vasculopathy in T-bet(-/-) mice. Interestingly, CD4 but not CD8 T cell deficiency in T-bet(-/-) mice affords dramatic protection from vasculopathy and facilitates long-term graft acceptance. This is the first study establishing that in the absence of Th1-mediated alloimmune responses, CD4 Th17 cells mediate an aggressive proinflammatory response culminating in severe accelerated allograft rejection and vasculopathy. These results have important implications for the development of novel therapies to target this intractable problem in clinical solid organ transplantation.

Background: Venous autografts used in cardiovascular surgery tend to deteriorate over time due to arteriosclerotic complications. Cadaveric vascular allografts represent a possible alternative for this application, but donor endothelial cells (ECs) and antigen presenting cells of the graft trigger alloresponses mediated by MHC class I (MHC I) antigen, leading to graft failure. Vascular allograft rejection might be prevented by reducing cell surface expression of MHC I and thereby lowering the immunogenicity of the grafts., Material and Methods: An Intrabody approach was used to reduce MHC I expression in vascular allografts. The efficacy of an adenovirus (Ad) carrying an anti-MHC I Intrabody gene (Ad-Intrabody) was first tested in vitro using rat aortic ECs. The effect of the Ad-Intrabody was then studied in vivo by a model of rat carotid artery transplantation. Grafts were analyzed 7 and 28 days after transplantation by immunohistochemistry and real time reverse transcriptase-polymerase chain reaction., Results: Ad-Intrabody gene transfer reduced MHC I surface expression of rat ECs and inhibited in vivo alloimmune responses to carotid allografts. Decreased T cell and macrophage infiltration was observed within Ad-Intrabody transduced arterial allografts at day 28. This was associated with an inhibition of intimal thickening formation. Analysis of mRNA showed diminished levels of T cell markers and Interferon-gamma expression in the Ad-Intrabody-treated group compared with control groups., Conclusions: Ex vivo adenoviral gene transfer of an Intrabody against MHC I into rat carotid arteries prior to transplantation reduced both graft arteriosclerosis and inflammation in the absence of any systemic immunosuppression.

Background: Due to the risk of vascular complications, the indication for heart transplantation (HTx) in patients with Marfan syndrome and end-stage heart disease remains controversial. We analyzed the results of such patients who underwent HTx at our institution., Methods: Ten patients with Marfan syndrome (median age 36, range 19 to 56 years) underwent HTx between March 1986 and December 2005. The primary vascular manifestation of Marfan syndrome was type-A aortic dissection in three patients and ascending aortic aneurysm in seven patients. All patients had undergone cardiovascular operations prior to transplantation. All had refractory heart failure (New York Heart Association class IV) before transplantation. Three patients underwent transplantation after ventricular assist device (VAD) support (left VAD, n = 2; biventricular assist device, n = 1)., Results: There were no perioperative deaths. Two patients died of causes unrelated to Marfan disease (pneumonia on day 27, n = 1; stroke on day 102, n = 1). One patient died due to type-B dissection 3.8 years posttransplantation and one due to rupture of an aortic arch aneurysm after 12.1 years. Two patients underwent thoracoabdominal aortic replacement for chronic dissection 14 and 20 months posttransplantation, respectively. Kaplan-Meier survival rate was 80% at 1 year and 64% at 10 years. The Kaplan-Meier freedom from reoperation was 100% at 1 year and 62.5% at 10 years., Conclusions: Heart transplantation in patients with Marfan syndrome results in good long-term survival, similar to that of patients without Marfan syndrome. Close follow-up and timely operation of aortic pathologies is mandatory. Reluctance to place these patients on a heart transplant waiting list appears not to be justified.

Recently, we demonstrated the capacity of allo-specific gene-engineered T lymphocytes as transport vehicle for therapeutic transgenes into allografts. In this study, the influence of viral IL-10 as therapeutic transgene was addressed. Lewis rat T-cell lines specific for DA rat alloantigens were engineered to express vIL-10 by using a retroviral gene expression system. Like T regulatory 1 cells, vIL-10 transgenic T lymphocytes express the phenotype CD4(+)25(+) and secrete, in addition to vIL-10, rat IL-10 and IFN-gamma but no IL-4. First, the capacity of vIL-10 transgenic T-cell lines to modulate alloantigen-specific immune responses was evaluated in vitro. In comparison to control MLR with no transgenic cells or equal numbers of control T(EGFP)-lymphocytes, the proliferation as well as production of IFN-gamma by naive responder cells were significantly diminished. Despite this regulatory capacity in vitro, T(vIL-10)-lymphocytes were not able, either alone or in combination with suboptimal doses of Cyclosporine A, to prolong the survival of either DA rat cardiac or renal allografts in Lewis rat recipients. These data demonstrate that intra-graft IL-10 over-expression is not sufficient to prolong allograft survival in a high-responder strain combination and that the regulatory capacity of T cells in vitro does not predict their in vivo efficiency.