A phase I/II dose-escalation multi-center study to evaluate the safety of infusion of natural killer cells or memory T cells as adoptive therapy in coronavirus pneumonia and/or lymphopenia: RELEASE study protocol. - García-García I; Guerra-García P; Ferreras C; Borobia AM; Carcas AJ; Queiruga-Parada J; Vicario JL; Mirones I; Solano C; Eguizabal C; Soria B; Pérez-Martínez A (Trials, 2021)