We are the first to broaden observations on the genetic control of HLA-DPB1 expression from BLCL and primary unstimulated B cells, in which this issue has been studied so far (5, 8), to other cell types likely to play a role in GvHD, such as DC and IFN-γ-stimulated B cells and monocytes. This evidence concerns the gene IFNG and graft versus host disease.