In the context of the immunosuppressive MM BM microenvironment, Tregs inhibit MM-specific T-cell effector functions through direct cell-to-cell contact and the secretion of IL10, TGFβ, and IL35, as well as cytolytic granzymes and perforins, to inhibit and/or kill immune effector cells [28,29,30]. Here, PRF1 is linked to Miyoshi myopathy.