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DFG Research Grant for PD Dr. Moritz Schmelzle
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Priv.-Doz. Dr. Moritz Schmelzle receives additional financial support for his project "CD39-dependent regulation of innate immune responses and modulation of exacerbated sterile inflammation in acute-on-chronic liver failure" (DFG Research Grant 299534341, SCHM2661/3-2).
Acute on chronic liver failure (ACLF) is defined as an acute hepatic insult in patients with chronic liver disease and is characterized by high death rates. Systemic inflammation is considered a hallmark of ACLF and can be linked to progression of liver failure and clinical deterioration. Criteria for ACLF and the systemic inflammatory response syndrome (SIRS) substantially overlap and support the assumption of mechanistic similarities between both syndromes. Thus, modulating inflammation and the linked immune responses in ACLF might help to restore homeostasis and improve of regenerative capacities of the injured liver.We hypothesize that the catalyzed hydrolysis of purinergic damage-associated molecular patterns (DAMPS), such as extracellular ATP, by the ectonucleotidase CD39 is crucially involved in the regulation of innate immune responses and the modulation of exacerbated sterile inflammation in ACLF. We here aim to describe characteristics and functions of monocyte subsets in ACLF and to investigate implications of purinergic signaling. We further plan to investigate the therapeutical relevance of non-classical monocytes and the immune-type ectonucleotidase CD39 in experimental ACLF. Finally, we will evaluate the clinical significance of cellular and non-cellular immune responses in ACLF patients enrolled in the GRAFT Trial.
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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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