IL15 and Miyoshi myopathy: Through the modification of the CAR-T-cell structure for IL-15 secretion, we were able to elevate the ratio of TCM cells and improved antitumor efficacy in the refined FCRL5 CAR-T/IL-15 model, which showed increased intertumoral CAR+ T-cell infiltration, reduced PD-1 expression, and potent tumor-suppressive effects in xenografts by days 28 and 35 post-treatment, validating the viability of this construct for targeted MM treatment.