Bettina Dresske

Multipotent Cells of Monocytic Origin Improve Damaged Heart Function

Recently, we generated cells with multipotent properties from blood monocytes that in vitro differentiate into various somatic cell types. This experimental study investigated whether these programmable cells of monocytic origin (PCMO) succeed to restore left ventricular function after myocardial infarction (MI).

Implications for the usage of the left lateral liver graft for infants ≤10 kg, irrespective of a large-for-size situation--are monosegmental grafts redundant?

Organ donor shortage for infant liver transplant recipients has lead to an increase in splitting and living donation. For cases in which even transplantation of the left lateral graft (Couinaud’s segments II + III) results in a “large for size situation” with an estimated graft body weight ratio (GBWR) of >4%, monosegmental liver transplantation was developed. This, however, bears complications because of greater parenchymal surface and suboptimal vascular flow. We exclusively use the left lateral graft from living donors or split grafts. Temporary abdominal closure is attempted in cases of increased pressure. We report of 41 pediatric transplants in 38 children ≤10 kg. Within this group, there were 23 cases with a GBWR of ≥4, and 15 cases with a GBWR <4. There was no statistical difference in vascular or biliary complications. Despite a more frequent rate of temporary abdominal closure, we did not find a higher rate of intra‐abdominal infections. Overall, patient and graft survival was excellent in both groups (one death, three re‐transplants). We noticed, however, that the ventro–dorsal diameter of the graft appears to be more relevant to potential graft necrosis than the actual graft size. In conclusion, the usage of monosegmental grafts seems unnecessary if transplantation of left lateral grafts is performed by an experienced multidisciplinary team, and temporary abdominal closure is favored in cases of increased abdominal pressure.

Future strategies for tolerance induction:: A comparative study between hematopoietic stem cells and macrophages

So far, clinical benefit of hematopoietic stem cell induced donor-specific tolerance across major histocompatibility complex (MHC) barriers was hampered by either graft rejection or graft-versus-host disease. An alternative approach focuses on the use of donor-derived cells that bear an inherent mechanism to circumvent allospecific rejection upon injection into non-immunosuppressed hosts. Using a myeloablative conditioning model in the rat, full donor chimeric recipients were generated and their potential to induce long-term cardiac allograft survival was compared with the fate of grafts transferred to non-immunosuppressed host rats pretreated with donor-macrophages derived from the peritoneal cavity in the LEW to DA inbred strain combination. The induction of full multilineage long-term donor-chimerism (> 150 days) after initial host conditioning using two doses of cyclophosphamide and one shot of busulphan prevented acute graft rejection, whereas non-chimeric animals experienced acute and complete rejection. Conversely, vigorous T-cell depletion is required to protect conditioned animals from lethal graft-versus-host disease. Instead, the use of donor intraperitoneal macrophages achieved a state of transient chimerism and subsequent long-term graft survival in fully immunocompetent rats without the need of lethal conditioning regimens. In conclusion, the complex immunologic interactions, observed after allogeneic bone marrow transplantation as a means to induce donor chimerism, and subsequent long-term graft acceptance can be avoided if appropriate cell populations can be identified that, by themselves, induce a transient state of donor chimerism prevailing long enough to deviate allospecific immune responses, as outlined in this study.

WOFIE stimulates regulatory T cells: a 2-year follow-up of renal transplant recipients.

Background. Initial interruption of immunosuppression for 72 hr was analyzed in renal transplant recipients according to Calne et al.s “window of opportunity for immunologic engagement” (WOFIE) concept. Methods. This pilot study was designed as a randomized, open-label, prospective trial of 40 recipients (20 in the WOFIE group, 20 in the control group) of cadaveric kidney transplants who were followed up for 2 years. Immunosuppression comprised tacrolimus (trough levels 5–8 ng/mL), daclizumab (1 mg per kilogram of body weight on day 0 and after 2, 4, 6, and 8 weeks), mycophenolate mofetil (1–2 g/day), and prednisolone (maintenance dose of 10 mg/day). After induction with daclizumab, prednisolone, and mycophenolate mofetil, immunosuppression was interrupted for 72 hr in the WOFIE group. Steroid withdrawal followed in both groups within 12 to 16 weeks posttransplant. Results. Patient and graft survival did not differ significantly between the two cohorts. However, the WOFIE group experienced less acute rejection episodes and developed better graft function. Although all but one of the patients in the WOFIE group successfully discontinued steroid treatment, permanent steroid withdrawal was achieved in only 76.4% of the control group. After daclizumab discontinuation, the WOFIE group demonstrated an increase of CD4+CD25+ T cells in peripheral blood (P<0.05 vs. control group), which was stable over time and strongly correlated with a significantly higher expression level of Foxp3-mRNA. Conclusions. Initial interruption of immunosuppression for 72 hr correlates with the induction of regulatory immunologic mechanisms and allows early and reliable minimization of immunosuppressive treatment.

Different in vivo tolerogenicity of MHC class I peptides.

The efficacy of MHC class I‐derived peptides to induce tolerance was tested in a cardiac transplantation model. Two 25‐mer peptides from the polymorphic region of the DA class I molecule (RT1.Aa) were synthesized by F‐moc chemistry and injected intrathymically or intraperitoneally into LEW (RT1.1) responder animals. Intrathymic treatment of the recipient animals with peptide 1 (residues 56–80) accompanied by intraperitoneal treatment with peptide 4 (residues 96–120) led to indefinite survival of allogeneic DA cardiac allografts (n = 7; >100 days). The tolerogenicity of both peptides differed according to the site of inoculation, as donor‐specific tolerance was only observed after administration of peptide 1 into the thymus and injection of peptide 2 into the abdominal cavity of LEW recipients, but not vice versa. Donor‐specific tolerance was confirmed in vivo by grafting of full‐thickness skin and in vitro by appropriate proliferation and cytotoxicity assays using donor and third‐party rats. Donor‐specific tolerance was associated with up‐regulation of interleukin‐4, transforming growth factor β, and interleukin‐10 gene expression within cardiac allografts, thus suggesting intrathymic clonal deletion and external suppression with expansion of T‐helper 2‐type lymphocytes as the underlying mechanisms of tolerance induction. J. Leukoc. Biol. 65: 16‐27; 1999.

Impact of RT1.C-encoded MHC antigens on host-versus-graft and graft versus-host reactions in a model of small bowel transplantation in the rat☆

Abstract Non-classical MHC-class I antigens encoded by rat RT1.C region genes have been demonstrated to have a strong in vitro and in vivo potential to trigger natural killer (NK) cell activity. 1,2 NK cells comprise a unique entity of lymphocytes that act as an important effector arm of the innate immune response. Nevertheless, NK cells distinguish non-self MHC-class I molecules on target cells in an allospecific fashion. 3 Target cell recognition of non-self MHC-class I molecules encoded by the RTI.C-locus of the RT1 gene complex induces activation of NK cells without the need of a prior sensitization process, an immune mechanism also referred to as allogeneic lymphocyte cytotoxicity (ALC). 4 By virtue of its vast mass of lymphatic tissue, heterotopic small bowel transplantation (SBTx) was performed between intra-MHC class I recombinant inbred rat strains, differing only at the RT1.C-locus, in order to show the impact of NK-related immune responses for this model of solid organ transplantation.

Evaluation Of Risk Factors In Intestinal Transplant Recipients

A195Aims:Intestinal transplantation (ITx) is an emerging technique for patients with irreversible loss of intestinal function and total parenteral nutrition (TPN) associated complications. Patients are often referred late with a complicated course during TPN.Methods:In the last 2 years, 10 patients

Zum Stellenwert der Toleranzentstehung durch Leber-passenger-leucocytes nach orthotoper Lebertransplantation chimärer und nicht-chimärer Leberorgane im Rattenmodell

Background: Hepatocyte-related MHC class I antigens as well as liver passenger leucocytes (PLs) are discussed as being responsible for spontaneous tolerance after orthotopic liver transplantation. For better differentiation of these liver-related cell populations chimeric liver transplants were induced to characterize their tolerogenicity after transplantation in allogeneic and syngeneic recipients. Methods: Orthotopic liver transplantation was performed in the following experimental groups using male inbred rats (n = 6): (1) DA (RT1.avl ) → LEW (RT1.1); (2) LEW → DA; (3) LEW → LEW; (4) LEW (10 Gy total body irradiation day — 7 ) → DA; (5) LEW (10 Gy total body irradiation day — 7 ) → LEW; (6) LEW (10 Gy total body irradiation day — 7 ) → LEW (parked in LEW for 36 h) → DA; (7) LEW (10 Gy total body irradiation day — 7 ) → DA (parked in DA for 36 h) → DA. Flow cytometric analysis and immunohistochemical staining with Ox-3 (LEW-MHC class II antigen) and MN4 (DA-MHC class I antigen) were performed to evaluate donor chimerism in various recipient organs and blood. Results: The mean survival differed significantly between the groups (M ± SD): (1) 11.2 ± 1.0; (2) >100; (3) >100; (4) 9.0 ± 0.5; (5) > 100; (6) 5/6 >100 and (7) 8.0 ± 1.5 days. Parking in the allogeneic recipient (DA) for 36 h failed to induce tolerance of LEW- liver grafts although these organs revealed a DA-specific PL population. Conversely, parking of the irradiated grafts in a syngeneic (LEW) recipient led to long-term graft survival after transplantation in allogeneic DA recipients. Despite tolerance induction liver-chimerism was not related to long-term chimerism in DA recipients (spleen, thymus and blood). Conclusions: Chimeric liver grafts with allogeneic parenchyma and syngeneic PLs are acutely rejected whereas the reconstitution of donor PLs again induced tolerance. These results prove the tolerogenicity of passenger leucocytes which is sensible to irradiation. Furthermore, it could be demonstrated that long-term chimerism is not substantial for the induction of organ-specific tolerance.