Although systemic T cell proliferation or local infiltration to GVHD organs was not significantly altered after BRNP treatment, the expression of ICOS and CTLA-4 on donor T cells as well as frequencies of- ICOS+ or CLTA-4+ donor T cells were reduced with BRNP treatment, suggesting that BRNP treatment may have blunted the activation of alloantigen reactive donor T cells post transplantation. This evidence concerns the gene ICOS and graft versus host disease.