Expression of checkpoint proteins PD-1 and LAG3 was also seen on CD70+ T cells, and although strong type 1 helper T cell (Th1) cytokine and cytotoxic phenotype suggests little functional exhaustion, this may explain the increased risk of GVHD associated with posttransplant PD-1 inhibition.30 Here, LAG3 is linked to graft versus host disease.