Furthermore, although CD4 T-cells recognize peptides presented in HLA class II molecules and HLA class II is only expressed on non-hematopoietic cells under inflammatory conditions, infusion of purified donor CD4 T-cells 3 months after TCD alloSCT with an HLA 10/10 matched, but HLA-DP mismatched donor can also result in severe GVHD caused by CD4 T-cells directed against the mismatched HLA-DP molecule from the patient (10). This evidence concerns the gene CD4 and graft versus host disease.