Support for this theory came from the experience of Blazar et al., who proved that the risk of graft versus host disease (GVHD) increased with the anti-PD-1 antibody compared with the CTLA-4 blockade and that the combination of anti-PD-1 and anti-CTLA-4 is responsible for more severe GVHD than monotherapy treatment. The gene discussed is CTLA4; the disease is graft versus host disease.