Thymic GVHD (tGVHD) is believed to contribute to extended and profound T cell deficiency and repertoire restriction after allo-BMT, but the cellular mechanisms of tGVHD, and interactions between donor alloreactive T cells and thymic tissues remain poorly defined. Using clinically relevant allo-BMT models, we are studying the kinetics of thymus-infiltrating alloreactive donor T cells in vivo with bioluminescence imaging (BLI). Furthermore, we are analyzing the role of molecules relevant for T cell trafficking, cytolytic function, and co-stimulation and co-inhibition of alloreactive T cells in tGVHD. We want to define specific pathways for cytolysis, trafficking and immune modulation involved in tGVHD as potential selective therapeutic targets to attenuate tGVHD and improve post-transplant T-cell reconstitution in patients with GVHD.

In collaboration with the Sadelain lab we developed a plasmid encoding a recombinant bidirectional lentiviral vector. The 5' to 3' unit encodes a NFAT enhancer/minimal b-globin promoter driving expression of click beetle red luciferase. The 3' to 5' unit encodes the human PGK-1 promoter driving expression of external gaussia luciferase. Using different substrates (Coelenterazine, D-Luciferin) we are able to distinguish between the constitutive gaussia-luciferase signal and the NFAT-inducible click-beetle luciferase signal in the BLI. We transduced hematopoietic stem cells and successfully transplanted them into lethally irradiated hosts. After immune reconstitution we are using the reporter+ BM and T cells to evaluate the impact of conditioning regimens on kinetic, severity and distribution of GVHD and to study the dependence of immune reconstitution on the type of donor graft transplanted.