RARA and graft versus host disease: We found that chronicvitamin A deficiency modifies the composition of T cell subsets in donor miceand significantly reduces the capacity of their T cells to cause lethal GVHD.Importantly, administration of a pan-RAR antagonist to donor mice caused atransient inhibition of donor T cell RAR signaling resulting in reduced T cellalloreactivity and a reduction in their ability to cause GVHD [39].