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Einstein Visiting Fellow Prof. Stefan G. Tullius
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Prof. Dr. Stefan G. Tullius, Harvard Medical School, became Einstein BIH Visiting Fellow at the Charité, Department of Surgery. 

Vascular Composite Tissue Allotransplantation (VCA) has developed from a pioneering endevour to a clinical reality during the last 15 years. More than 150 extremity, face, knee, and most recently uterus and penis transplants have been performed during the last 15 years. VCA activities have been seen around the globe. Although feasibility of the procedure has been shown, it is still emerging and far from being a standard clinical procedure. 

The Charité has been an international leader in transplantation research for decades. However, neither VCA basic clinical research programs are currently offered in Berlin or Germany in a meaningful way.The involvement of Prof. Tullius as an Einstein BIH Visiting Fellow is expected to synergize and accelerate efforts igniting both a clinical research transplant program and a basic research group of excellence. The overall objective of our integrated basic and clinical research working group Vascular Composite Tissue Transplantation has three main goals:

To establish a basic Research group of Excellence: VCAs offer unique opportunities to study novel aspects of antigenicity, immune modulation and neo-vascularization. One important aspect that distinguishes VCA from solid organ transplants is their blood supply through a vascularized arterial in- and venous outflow in addition to sprouting new vessels at the large interface of VCA with recipient tissue.

To establish a clinical bio-repository as a pre-requisite for a clinical research VCA program.

To implement a clinical VCA research program (hand, abdominal wall, uterus) as a multi- disciplinary and translational effort.

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Our manuscript "Depletion of donor dendritic cells ameliorates immunogenicity of both skin and hind limb transplants" has been accepted for publication in Frontiers in Immunology, section Alloimmunity and Transplantation. Authors are Muhammad Imtiaz Ashraf, Joerg Mengwasser, Anja Reutzel-Selke, Dietrich Polenz, Kirsten Führer, Steffen Lippert, Peter Tang, Edward Michaelis, Rusan Catar, Johann Pratschke, Christian Witzel, Igor M. Sauer, Stefan G. Tullius, and Barbara Kern.

Acute cellular rejection remains a significant obstacle affecting successful outcomes of organ transplantation including vascularized composite tissue allografts (VCA). Donor antigen presenting cells (APC), particularly dendritic cells (DC), orchestrate early alloimmune responses by activating recipient effector T cells. Employing a targeted approach, we investigated the impact of donor-derived conventional DC (cDC) and APC on the immunogenicity of skin and skin-containing VCA grafts, using mouse models of skin and hind limb transplantation.
By post-transplantation day 6, skin grafts demonstrated severe rejections, characterized by predominance of recipient CD4 T cells. In contrast, hind limb grafts showed moderate rejection, primarily infiltrated by CD8 T cells. While donor depletion of cDC and APC reduced frequencies, maturation, and activation of DC in all analysed tissues of skin transplant recipients, reduction in DC activities was only observed in the spleen of hind limb recipients. Donor cDC and APC depletion did not impact all lymphocyte compartments but significantly affected CD8 T cells and activated CD4 T in lymph nodes of skin recipients. Moreover, both donor APC and cDC depletion attenuated the Th17 immune response, evident by significantly reduced Th17 (CD4+IL-17+) cells in the spleen of skin recipients and reduced levels of IL-17E and lymphotoxin-α in the serum samples of both skin and hind limb recipients. In conclusion, our findings underscore the highly immunogenic nature of skin component in VCA. The depletion of donor APC and cDC mitigates the immunogenicity of skin grafts while exerting minimal impact on VCA.

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