Induction of tolerance can be achieved with Modified Immune Cells (MIC) by infusion of mononuclear cells challenged with mitomycin C (MMC). Although MIC treatment has been successful in several animal models for autoimmunity and in clinical studies of solid organ transplantation, the mechanism of immunosuppression is not fully elucidated. In lupus nephritis, the glomerular deposition of immune complexes is associated with accumulating immune cells in the kidney. The infiltrating immune cells frequently establish tertiary lymphoid structures (TLS) supporting adaptive autoimmune responses toward locally displayed antigens. Since TLS display a high persistence to peripheral B cell depletion, the destruction of TLS presents an essential treatment goal in lupus nephritis. In this study, we used lupus nephritis prone NZB/W F1 mice to show the destruction of TLS in the kidney after MIC treatment. Independent of treatment, >86% of animals displayed dense lymphocytic aggregates proximal to the pelvic wall of the medulla and the arcuate arteries within the cortex of kidneys. Cell type composition of TLS changed drastically after MIC treatment leading to diminished B-cells, a decreased B-cell/T-cell ratio, and a T cell dominated phenotype. Furthermore, a loss of organization of the TLS was observed after MIC treatment. The strict separation of B-cell and T-cell areas was abrogated, and germinal centers were disintegrated. However, regulatory T-cells remained unchanged indicative of a B-cell centric treatment mechanism. Our data provides a putative in vivomechanism how MIC treatment inhibits progression of active lupus nephritis by the destruction of tertiary lymphoid structures within the kidney. Commercial Support - TolerogenixX GmbH

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Significance Statement In previous work, the authors demonstrated that kidney transplant recipients developed donor-specific unresponsiveness when they were given a pretransplant infusion of modified donor-derived PBMCs. In this study, they provide evidence that the immunosuppressive properties of these cells persist and the donor-specific unresponsiveness is long-lasting. In the four patients who received the highest dose of the modified immune cells, administration of these cells was associated with a striking increase in IL-10–producing regulatory B lymphocytes and evidence of the consensus gene expression signature of operational tolerance. In vitro , donor-specific unresponsiveness was abolished after B lymphocyte depletion, suggesting a direct pathophysiologic role for regulatory B lymphocytes. These findings support the notion that modified donor-derived PBMCs may be useful in kidney transplantation, but this approach requires further validation and rigorous controlled randomized studies. Background We recently demonstrated that donor-derived modified immune cells (MICs)—PBMCs that acquire immunosuppressive properties after a brief treatment—induced specific immunosuppression against the allogeneic donor when administered before kidney transplantation. We found up to a 68-fold increase in CD19 + CD24 hi CD38 hi transitional B lymphocytes compared with transplanted controls. Methods Ten patients from a phase 1 clinical trial who had received MIC infusions before kidney transplantation were followed to post-transplant day 1080. Results Patients treated with MICs had a favorable clinical course, showing no donor-specific human leukocyte antigen antibodies or acute rejections. The four patients who had received the highest dose of MICs 7 days before surgery and were on reduced immunosuppressive therapy showed an absence of in vitro lymphocyte reactivity against stimulatory donor blood cells, whereas reactivity against third party cells was preserved. In these patients, numbers of transitional B lymphocytes were 75-fold and seven-fold higher than in 12 long-term survivors on minimal immunosuppression and four operationally tolerant patients, respectively ( P <0.001 for both). In addition, we found significantly higher numbers of other regulatory B lymphocyte subsets and a gene expression signature suggestive of operational tolerance in three of four patients. In MIC-treated patients, in vitro lymphocyte reactivity against donor blood cells was restored after B lymphocyte depletion, suggesting a direct pathophysiologic role of regulatory B lymphocytes in donor-specific unresponsiveness. Conclusions These results indicate that donor-specific immunosuppression after MIC infusion is long-lasting and associated with a striking increase in regulatory B lymphocytes. Donor-derived MICs appear to be an immunoregulatory cell population that when administered to recipients before transplantation, may exert a beneficial effect on kidney transplants. Clinical Trial registry name and registration number: MIC Cell Therapy for Individualized Immunosuppression in Living Donor Kidney Transplant Recipients (TOL-1), NCT02560220

Background:The administration of modified immune cells (MIC) before kidney transplantation led to specific immunosuppression against the allogeneic donor and a significant increase in regulatory B lymphocytes. We wondered how this approach affected the continued clinical course of these patients.Methods:Ten patients from a phase I clinical trial who had received MIC infusions prior to kidney transplantation were retrospectively compared to 15 matched standard-risk recipients. Follow-up was until year five after surgery.Results:The 10 MIC patients had an excellent clinical course with stable kidney graft function, no donor-specific human leukocyte antigen antibodies (DSA) or acute rejections, and no opportunistic infections. In comparison, a retrospectively matched control group receiving standard immunosuppressive therapy had a higher frequency of DSA (log rank P = 0.046) and more opportunistic infections (log rank P = 0.033). Importantly, MIC patients, and in particular the four patients who had received the highest cell number 7 days before surgery and received low immunosuppression during follow-up, continued to show a lack of anti-donor T lymphocyte reactivity in vitro and high CD19+CD24hiCD38hi transitional and CD19+CD24hiCD27+ memory B lymphocytes until year five after surgery.Conclusions:MIC infusions together with reduced conventional immunosuppression were associated with good graft function during five years of follow-up, no de novo DSA development and no opportunistic infections. In the future, MIC infusions might contribute to graft protection while reducing the side effects of immunosuppressive therapy. However, this approach needs further validation in direct comparison with prospective controls.Trial registration:https://clinicaltrials.gov/, identifier NCT02560220 (for the TOL-1 Study). EudraCT Number: 2014-002086-30.

Introduction Donor-derived modified immune cells (MIC) induced long-term specific immunosuppression against the allogeneic donor in preclinical models of transplantation. In a phase I clinical trial (TOL-1 Study), MIC treatment resulted in a cellular phenotype that was directly and indirectly suppressive to the recipient’s immune system allowing for reduction of conventional immunosuppressive therapy. Here, we describe a protocol for a randomised controlled, multicentre phase-IIb clinical trial of individualised immunosuppression with intravenously administered donor MIC compared with standard-of-care (SoC) in living donor kidney transplantation (TOL-2 Study). Methods and analysis Sixty-three living donor kidney transplant recipients from six German transplant centres are randomised 2:1 to treatment with MIC (MIC group, N=42) or no treatment with MIC (control arm, N=21). MIC are manufactured from donor peripheral blood mononuclear cells under Good Manufacturing Practice conditions. The primary objective of this trial is to determine the efficacy of MIC treatment together with reduced conventional immunosuppressive therapy in terms of achieving an operational tolerance-like phenotype compared with SoC 12 months after MIC administration. Key secondary endpoints are the number of patient-relevant infections as well as a composite of biopsy-proven acute rejection, graft loss, graft dysfunction or death. Immunosuppressive therapy of MIC-treated patients is reduced during follow-up under an extended immunological monitoring including human leucocyte antigen-antibody testing, and determination of lymphocyte subsets, for example, regulatory B lymphocytes (Breg) and antidonor T cell response. A Data Safety Monitoring Board has been established to allow an independent assessment of safety and efficacy. Ethics and dissemination Ethical approval has been provided by the Ethics Committee of the Medical Faculty of the University of Heidelberg, Heidelberg, Germany (AFmu-580/2021, 17 March 2022) and from the Federal Institute for Vaccines and Biomedicines, Paul-Ehrlich-Institute, Langen, Germany (Vorlage-Nr. 4586/02, 21 March 2022). Written informed consent will be obtained from all patients and respective donors prior to enrolment in the study. The results from the TOL-2 Study will be published in peer-reviewed medical journals and will be presented at symposia and scientific meetings. Trial registration number NCT05365672.

There are two main enzymes that convert tryptophan (Trp) to kynurenine (Kyn): tryptophan-2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO). Kyn accumulation can promote immunosuppression in certain cancers. In this study, we investigated Trp degradation to Kyn by IDO and TDO in primary human hepatocytes (PHH) and tumoral HepG2 cells. To quantify Trp-degradation and Kyn-accumulation, using reversed-phase high-pressure liquid chromatography, the levels of Trp and Kyn were determined in the culture media of PHH and HepG2 cells. The role of IDO in Trp metabolism was investigated by activating IDO with IFN-γ and inhibiting IDO with 1-methyl-tryptophan (1-DL-MT). The role of TDO was investigated using one of two TDO inhibitors: 680C91 or LM10. Real-time PCR was used to measure TDO and IDO expression. Trp was degraded in both PHH and HepG2 cells, but degradation was higher in PHH cells. However, Kyn accumulation was higher in the supernatants of HepG2 cells. Stimulating IDO with IFN-γ did not significantly affect Trp degradation and Kyn accumulation, even though it strongly upregulated IDO expression. Inhibiting IDO with 1-DL-MT also had no effect on Trp degradation. In contrast, inhibiting TDO with 680C91 or LM10 significantly reduced Trp degradation. The expression of TDO but not of IDO correlated positively with Kyn accumulation in the HepG2 cell culture media. Furthermore, TDO degraded L-Trp but not D-Trp in HepG2 cells. Kyn is the main metabolite of Trp degradation by TDO in HepG2 cells. The accumulation of Kyn in HepG2 cells could be a key mechanism for tumor immune resistance. Two TDO inhibitors, 680C91 and LM10, could be useful in immunotherapy for liver cancers.

There are two main enzymes that convert tryptophan (Trp) to kynurenine (Kyn): tryptophan-2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO). Kyn accumulation can promote immunosuppression in certain cancers. In this study, we investigated Trp degradation to Kyn by IDO and TDO in primary human hepatocytes (PHH) and tumoral HepaRG cells. To quantify Trp-degradation and Kyn-accumulation, using reversed-phase high-pressure liquid chromatography, the levels of Trp and Kyn were determined in the culture media of PHH and HepaRG cells. The role of IDO in Trp metabolism was investigated by activating IDO with IFN-γ and inhibiting IDO with 1-methyl-tryptophan (1-DL-MT). The role of TDO was investigated using one of two TDO inhibitors: 680C91 or LM10. Real-time PCR was used to measure TDO and IDO expression. Trp was degraded in both PHH and HepaRG cells, but degradation was higher in PHH cells. However, Kyn accumulation was higher in the supernatants of HepaRG cells. Stimulating IDO with IFN-γ did not significantly affect Trp degradation and Kyn accumulation, even though it strongly upregulated IDO expression. Inhibiting IDO with 1-DL-MT also had no effect on Trp degradation. In contrast, inhibiting TDO with 680C91 or LM10 significantly reduced Trp degradation. The expression of TDO but not of IDO correlated positively with Kyn accumulation in the HepaRG cell culture media. Furthermore, TDO degraded L-Trp but not D-Trp in HepaRG cells. Kyn is the main metabolite of Trp degradation by TDO in HepaRG cells. The accumulation of Kyn in HepaRG cells could be a key mechanism for tumor immune resistance. Two TDO inhibitors, 680C91 and LM10, could be useful in immunotherapy for liver cancers.

Zusammenfassung Hintergrund Vaskularisierte Composite Allotransplantationen (VCA) ermöglichen die Wiederherstellung komplexer Gewebedefekte. Die ersten erfolgreichen allogenen Hand- und Gesichtstransplantationen haben die Forschung zur Verbesserung der immunsuppressiven Therapien stetig vorangetrieben. Die Inkubation mononukleärer Zellen des peripheren Blutes (PBMCs) mit Mitomycin C (MMC) generiert immunmodulatorisch wirksame Zellen (MICs). In vorherigen Studien konnten wir eine signifikante immunsuppressive Wirkung durch die Applikation von Donor-MICs am Tag der Transplantation zeigen. Ziel dieser Studie ist es, den optimalen Zeitpunkt der Behandlung mit MICs in der VCA zu eruieren. Material und Methoden 60 allogene Hinterlauftransplantationen wurden in 6 experimentellen Gruppen durchgeführt. Lewis-Ratten (LEW) dienten als Spender-, Brown-Norway-Ratten (BN) als Empfängertiere. Tieren der Gruppe A wurden einmalig Spender-MICs 7 Tage präoperativ systemisch verabreicht. Gruppe B-F dienten als Kontrollgruppen. Tiere der Gruppe B erhielten keine immunsuppressive Therapie. In Gruppe C wurden unbehandelte Spender-PBMCs 7 Tage präoperativ verabreicht. Tiere der Gruppe D erhielten nur das Zellkulturmedium. Tieren der Gruppe E wurde eine Standardimmunsuppression mit Tacrolimus und Prednisolon verabreicht. In Gruppe F wurden syngene Hinterlauftransplantationen (BN→BN) durchgeführt. Der Abstoßungszeitpunkt wurde sowohl anhand klinischer Beobachtungen als auch aufgrund histologischer Parameter bestimmt. Ergebnisse In Versuchsgruppe A zeigte sich im Vergleich zu den Kontrollgruppen B, C und D (5,5 ± 0,7, 5,3 ± 0,7 und 5,7 ± 0,5) eine signifikant früher eintretende Abstoßungsreaktion der Hinterläufe nach 3,5 ± 0,2 Tagen (p < 0,01). In den Kontrollgruppen E und F zeigte sich keine Abstoßungsreaktion. Schlussfolgerung Die Ergebnisse der vorliegenden Studie zeigen, dass die immunmodulatorische Wirkung von MICs unmittelbar vom Applikationszeitpunkt abhängt. Nachdem in vorherigen Experimenten die Applikation von MICs am Transplantationstag eine signifikante immunsuppressive Wirkung aufwies, konnte im Rahmen dieser Studie gezeigt werden, dass die präoperative Gabe von MICs zu einer beschleunigten Abstoßung führt und damit das Überleben des Transplantates signifikant verkürzt wird. Folgestudien sind notwendig, um sowohl die Modifikation des Applikationszeitpunktes als auch die Dosis-Effekt-Beziehungen und Zellcharakteristika dieser potentiell immunsuppressiven Zellen weiter zu untersuchen.

Background Vascularized Composite Allotransplantation (VCA) enables the restoration of complex tissue defects. Since the first successful hand and face transplants were performed, clinical and experimental research has consistently improved immunosuppressive therapies. The incubation of peripheral blood mononuclear cells (PBMCs) with mitomycin C (MMC) results in immunomodulatory cells (MICs). In previous studies, the systemic application of MICs on the day of allogeneic hind limb transplantation led to a significant immunosuppression in rats. The aim of this study is to further investigate the optimal point in time of MIC application in a complex VCA model.Material and Methods In six groups, 60 allogeneic hind limb transplantations were performed. Fully mismatched rats were used as hind limb donors [Lewis (LEW)] and recipients [Brown-Norway (BN)]. Group A received donor-derived MICs seven days preoperatively. Group B received no immunosuppression; group C received untreated PBMCs seven days prior to transplantation. Animals in group D received cell culture media, whereas group E was treated with a standard immunosuppression consisting of tacrolimus and prednisolone. In group F, syngeneic hind limb transplantations (BN -> BN) were performed. Transplant rejection was assessed clinically and histologically.Results Group A showed a significantly earlier onset of allograft rejection after 3.5 +/- 0.2 days (p < 0.01) when compared with control groups B, C and D (5.5 +/- 0.7, 5.3 +/- 0.7 und 5.7 +/- 0.5). Groups E and F showedno allograft rejection.Conclusion This study shows that the time of application determines the immunomodulatory effects of MICs. Whereas the systemic application of MICs on the day of transplantation led to a significant immunosuppression in previous studies, this study demonstrates that preoperative injections of MICs lead to an acceleration of allotransplant rejection. Follow-up studies are necessary to investigate further modifications of application time as well as dose-effect relations and cell characteristics of these potential immunosuppressive cells.

Spontaneous or operational tolerance is a phenomenon that rarely occurs in nature. By establishing a permanent "artificial" chimerism in a transplant recipient, tolerance to the specific donor can be reliably established; however, this comes at the price of a costly and burdensome induction therapy and the risk of developing graft-versus-host disease. Newer approaches with so-called advanced therapy medicinal products (ATMP) rely only on a short-term chimerism, which leads to a permanent graft acceptance via the increase of regulatory cell populations. In this context, therapy with regulatory T cells seem to be promising and these can possibly be further improved in the future by introducing a chimeric antigen receptor, so-called A2-CAR-Treg (regulatory T cells). Another approach represents therapy with modified immune cells (MIC) starting from monocytes. In the recipient these cells lead to a reduction of the donor-specific T cell response and to the formation of regulatory B lymphocytes. Ideally, regulatory cell products will in the future be able to reduce or completely replace drug-induced immunosuppression in transplantation and autoimmune diseases. Regulatory B lymphocytes appear to play an important role in the context of establishing durable transplant acceptance.

Eine spontane oder operationale Toleranz ist ein in der Natur selten vorkommendes Phänomen. Durch die Etablierung eines dauerhaften „künstlichen“ Chimärismus bei einem Transplantatempfänger kann eine Toleranz gegen den spezifischen Spender jedoch zuverlässig etabliert werden. Dies geschieht allerdings zum Preis einer aufwendigen und belastenden vorbereitenden Therapie sowie der Gefahr der Entwicklung einer Graft-versus-Host-Erkrankung. Neuere Ansätze mit sog. ATMP („advanced therapy medicinal products“) setzen nur auf einen kurzzeitigen Chimärismus, der über den Anstieg regulatorischer Zellpopulationen zu einer dauerhaften Transplantatakzeptanz führt. Vielversprechend scheinen in diesem Zusammenhang Therapien mit regulatorischen T‑Zellen zu sein, diese können möglicherweise in Zukunft durch Einbringung eines chimären Antigenrezeptors (CAR) weiter verbessert werden (sog. A2-CAR-Treg [„regulatory T cells“]). Einen anderen Ansatz stellt die Therapie mit MIC („modified immune cells“), ausgehend von Monozyten, dar. Diese Zellen führen beim Empfänger zu einer Reduktion der spenderspezifischen T‑Zell-Antwort und zur Ausbildung regulatorischer B‑Lymphozyten. Idealerweise sind regulatorische Zellprodukte zukünftig in der Lage, medikamentöse Immunsuppression bei Transplantation und Autoimmunerkrankungen einzusparen oder vollständig zu ersetzen. Regulatorische B‑Lymphozyten scheinen eine wichtige Rolle im Zusammenhang mit der Etablierung einer dauerhaften Transplantatakzeptanz zu spielen.

Anti-thyroid antibodies (atbs) (anti-TPO, anti-TG, anti-TRH receptor) are autoatbs that recognize specific antigens that belong to thyroid structures. Several mechanisms were proposed to explain the breaking of immunotolerance to thyroid antigens. Our previous studies showed that IgG-anti-F(ab)2 atbs exert immunosuppresives effect in vitro and inverse correlate with autoatbs in certain autoimmune diseases. Relying on sera from pregnant women with and without anti-thyroid atbs, respectively with or without spontaneous pregnancy loss we intended to analyze the IgG-anti-F(ab)2 atbs titers in sera of these categories of patients. The lot of patients consists of 126 pregnant women out of which 47 had a normal course of pregnancy and 79 experienced spontaneous abortion. Anti-TPO, anti-TG, and IgG-anti-F(ab)2 atbs titers were measured in sera of these women. Although a difference was found between IgG-anti-F(ab)2 atbs titer in pregnant women with positive versus negative anti-thyroid atbs, this was not statistically significant. IgG-anti-F(ab)2 atbs titer is higher in women with a normal course of pregnancy compared to women spontaneous pregnancy loss. Differently from other autoimmune diseases, our data show that IgG-anti-F(ab)2 atbs are not inversely correlated to anti-thyroid atbs titers. Higher IgG-anti-(Fab)2 atbs titers were found in pregnant women with normal course of pregnancy compared with those with pregnancy loss.

BACKGROUND Preclinical experiments have shown that donor blood cells, modified in vitro by an alkylating agent (MIC, modified immune cells), induced long-term specific immunosuppression against the allogeneic donor. METHODS In this phase-I trial, patients received either 1.5x106 MIC per kg b.w. on day -2 (N=3, group A), or 1.5x108 MIC per kg b.w. on day -2 (N=3, group B) or day -7 (N=4, group C) before living donor kidney transplantation in addition to post-transplant immunosuppression. Primary outcome measure was the frequency of adverse events (AE) until day 30 (study phase) with follow-up to day 360. RESULTS MIC infusions were extremely well tolerated. During the study phase, a total of 69 AE occurred in 10 treated patients which were unlikely/not related to MIC infusion. No donor-specific human leukocyte antigen antibodies or rejection episodes were noted even though the patients received up to 1.3x1010 of donor mononuclear cells prior to transplantation. Group C patients with low immunosuppression during follow-up showed no in vitro reactivity against stimulatory donor blood cells on day 360 while reactivity against third party cells was preserved. Frequencies of CD19+CD24highCD38high transitional B lymphocytes (Breg) increased from a median of 6% before MIC infusion to 20% on day 180, which was 19- and 68-fold higher, respectively, than in two independent cohorts of transplanted controls. The majority of Breg produced immunosuppressive cytokine IL-10. MIC-treated patients showed the Immune Tolerance Network operational tolerance signature. CONCLUSION MIC administration was safe and could be a future tool for the targeted induction of tolerogenic Breg.

Inflammatory mechanisms are involved in achieving a normal pregnancy and in the development of certain pregnancy complications. These changes are more intense in pregnant women that suffer of pregnancy complications, such as spontaneous preterm birth (SPB). This study compared the course of inflammatory markers (IM) [neopterin (Neo), neopterin/creatinine ratio (Neo/Cre), C-reactive protein (CRP), and chitotriosidase (Chito)] serum concentration in the early pregnancy of women with birth at term (BT) and preterm birth (PB). IM concentration was measured in 90 sera sampled from 45 pregnancies with BT and 30 sera from 15 pregnancies with PB. Two sera were sampled from each pregnant woman: one in the first trimester and another one in the second trimester. Early pregnancy IM concentration showed a direct correlation with gestational age: Neo (rho=0.262, P=0.004), Neo/Cre (rho=0.372, P<0.001), CRP (rho=0.187, P=0.041), and Chito (rho=0.039, P=0.66). The correlation was present in both categories of patients with BT and PB. Patients with PB before 34 week of pregnancy (wp) and 32 wp showed higher Neo and Neo/Cre concentration than BT patients. A significant association was found between the risk of PB before 34 wp, PB before 32 wp, and Neo concentration (PB <34 wp: odds ratio (OR) =5.13, P=0.035) (PB <32 wp: OR=8.2, P=0.020) and, respectively, Neo/Cre concentration (PB <34 wp: OR=5.29, P=0.015) (PB <32 wp: OR=9.25, P=0.006). No association between CRP or Chito and PB age was found. IM concentration correlates with the gestational age at the time of blood sampling. Increased Neo and Neo/Cre concentration are associated with PB. Further studies are needed to evaluate the usefulness of these markers in clinical practice.

Christian Morath, Anita Schmitt, Christian Kleist, Volker Daniel, Gerhard Opelz, Caner Süsal, Florian K€alble, Luiza Pego da Silva, Claudia Sommerer, Lei Wang, Angela Hückelhoven, Uta Merle, Arianeb Mehrabi, Carsten Müller-Tidow, Martin Zeier, Michael Schmitt, Matthias Schaier, Peter Terness Gastroenterology, University of Heidelberg, Heidelberg, Germany, Hematology, University of Heidelberg, Heidelberg, Germany, Nephrology, University of Heidelberg, Heidelberg, Germany, Surgery, University of Heidelberg, Heidelberg, Germany and Transplantation Immunology, University of Heidelberg, Heidelberg, Germany