PDCD1 and Miyoshi myopathy: In studies of MM patients, Benson et al. found upregulation of PD-1 on NK cells in conjunction with PD-L1 expression on MM cells, and in vitro treatment with an anti-PD-1 mAb enhanced NK cell conjugation with PD-L1-expressing MM target cells, resulting in enhanced cytotoxicity and IFN-γ production (147).