Tu101 - A Novel Organotypic Model of Skin Rejection

Vascularized composite allografts (VCAs), such as hand, leg, abdominal wall, and face, involve the transplantation of multiple tissue types including skin, fat, bone, and muscle as a single anatomic unit. Despite similar immunosuppressive regimens as organ transplants, VCAs undergo significantly higher rates of rejection compared to solid organ allografts, a phenomenon attributed to the immunogenicity of the skin component of VCAs. To study this process, we have developed an organotypic model of skin rejection by adapting a recently described immune organoid system where dissociated human tonsils are used to form organoids capable of recapitulating primary and recall immune responses. Using this system, we co-culture intact human skin with tonsil organoids derived from an allogeneic donor. After seven days of co-culture we find that tonsil T-cells actively infiltrate into allogeneic skin and are located throughout the dermis and epidermis. Infiltrating tonsil T-cells express markers of recent activation (PD-1, HLA-DR), proliferate, and exhibit a restricted TCR repertoire. Further, infiltration of allogeneic tonsil T-cells is associated with skin tissue damage and cell death. Lastly, we find that clinically used immunosuppressive medications (cyclosporine, tacrolimus, and mycophenolate) reduce both infiltration of allogeneic tonsil T-cells into skin as well as subsequent tissue damage. Overall, we report a novel fully human in vitro model of skin rejection that can facilitate the screening and discovery of new therapeutic targets.