By utilising mouse splenocytes as a rich source of murine T‐cells, in addition to ex vivo expanded human Vγ9Vδ2 T‐cells, we show that MPO pretreatment reduced both human and mouse MM PC‐specific T‐cell cytotoxicity, corresponding to a decrease in IFN‐γ‐producing cells. The gene discussed is MPO; the disease is Miyoshi myopathy.