PDCD1LG2 and myocarditis: For example, a combined knockout of PD-L1/PD-L2 in C57BL/6 mice, which present a rather autoimmune-resistant model, revealed no cardiac phenotype (Keir et al., 2006), whereas Grabie et al. have shown that a transient inflammation of the heart in C57BL/6 mice (Grabie et al., 2007), induced by transgenic cytotoxic T lymphocytes (CTLs) directed against cardiac myocytes, can be transformed to lethal myocarditis by PD-L1 blockade.