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, A. M.; Carcas, A. J.; Queiruga-Parada, J.; Vicario, J. L.; Mirones, I.; Solano, C.; Eguizabal, C.; Soria, B.; Pérez-Martínez, A. (Trials, 2021)