BLI demonstrate a distinct distribution pattern for alloreactive donor T cells in allogeneic BMT recipients, Allogeneic Balb/c recipients show a strong signal on day 4 post-transparent after transfer of 10×10⁸ luc⁺ splenocytes as measured by total body photon emission. Ex vivo imaging confirms the infiltration of luc⁺ splenocytes to the thymus.