In vivo imaging of differences in early donor cell proliferation in graft-versus-host disease hosts with different pre-conditioning doses.

Graft-versus-host disease (GVHD) results from immunemediated attacks on recipient tissues by donor-originated cells through the recognition of incompatible antigens expressed on host cells. The pre-conditioning irradiation dose is a risk factor influencing GVHD severity. In this study, using newly generated luciferase transgenic mice on a B6 background (B6.Luc(Tg)) as bone marrow and splenocyte donors, we explored the effects of irradiation doses on donor cell dynamics in major histocompatibility complex (MHC)-matched allogeneic GVHD hosts via bioluminescence imaging (BLI). Results from BLI of GVHD hosts showed higher emission intensities of luminescence signals from hosts irradiated with 900 cGy as compared with those irradiated with 400 cGy. In particular, BLI signals from target organs, such as the spleen, liver, and lung, and several different lymph nodes fluctuated with similar time kinetics soon after transplantation, reflecting the synchronous proliferation of donor cells in the different organs in hosts irradiated with 900 cGy. The kinetic curves of the BLI signals were not synchronized between the target organs and the secondary organs in hosts irradiated with 400 cGy. These results demonstrate that pre-conditioning doses influence the kinetics and degree of proliferation in the target organs soon after transplantation. The results from this study are the first describing donor cell dynamics in MHC-matched allogeneic GVHD hosts and the influence of irradiation doses on proliferation dynamics, and will provide spatiotemporal information to help understand GVHD pathophysiology.