Furthermore, the most effective dosing schema of PTCy both reduced host-alloreactive (Vβ6+) donor CD4+CD25−Foxp3− effector T-cell proliferation at day +7 and allowed preferential donor CD4+CD25+Foxp3+ regulatory T-cell reconstitution at day +21, which together may serve as potential biomarkers of effective GVHD prevention by PTCy (79). Here, CD4 is linked to graft versus host disease.