CTLA4 and myocarditis: However, one study found that mating knockout PD-1 mice with knockout CTLA-4 mice produced Ctla4 +/- Pdcd1 −/− offspring mice that were more suitable for ICI myocarditis studies, and such mice showed more pronounced and clinically similar changes in cardiac injury relative to simultaneous knockout PD-1/CTLA-4 mice [92–95].