CD8A and graft versus host disease: CD8 T cells are important mediators of acute GVHD and GVT effects following alloSCT due to their capacity to cross-react at high frequency with polymorphic variants of MHC class I molecules [3], and recognize polymorphic peptides derived from non-MHC proteins (i.e., minor H antigens) in the context of self MHC class I molecules [4].