CORE 3 SUMMARY/ABSTRACT Core 3 supports the clinically oriented translational studies in this PPG. In this renewal application, all three projects share an integrated, synergistic focus on GI GVHD. Core 3 has developed new services related to GI GVHD in order to meet this increased focus of all three projects. The first creates a consolidated GI pathology core for both human and mouse samples and services all three projects. These central pathology services provide continuity of analyses across species, ensuring that the mechanistic studies in Projects 1 and 2 relate as closely as possible to the analysis of human samples in Project 3. The second new service creates a multi-center clinical database and repository, significantly expanding the previous single center database and repository. We have assembled a consortium of eight major transplant centers (four in the USA: University of Michigan, Ohio State University, Mayo Clinic, and University of Pennsylvania; and four in Germany: Regensburg, Dresden, Hamburg, and Würzburg). Our new consortium, called MAGIC (Michigan Acute GVHD International Consortium), will accelerate research in GVHD by integrating clinical and laboratory findings from more than 800 allogeneic BMT recipients annually. The linkage of biologic samples with detailed clinical data from multiple sites helps ensure that our analyses and clinical trial results will be generalizable throughout the BMT community. The third new service of this core builds upon the major accomplishment from the last cycle, the development of the first validated GVHD biomarker-based grading system (Ann Arbor GVHD Grading). Core 3 will perform the ELISA assays, including (for US centers) the real time Ann Arbor grading, which is needed to identify eligible patients for experimental GVHD clinical treatment trial in Project 3. Core 3 supports the translational studies in this PPG. In this renewal application, all three projects share an integrated, synergistic focus on GI GVHD. Core 3 has developed new services related to GI GVHD in order to meet this increased focus of all three projects. The first creates a consolidated GI pathology core for both human and mouse samples and services all three projects. These central pathology services provide continuity of analyses across species, ensuring that the mechanistic studies in Projects 1 and 2 relate as closely as possible to the analysis of human samples in Project 3