Compositions, methods, expression vectors and engineered immune cells for improving therapies that entail the administration of allogeneic cells to a patient. An immune cell, e.g., a T cell, modified to comprise and/or express FasL protein or a FasL protein derivative from, for example, an expression vector comprising a polynucleotide that encodes FasL protein or a FasL protein derivative, and to express FasR at a reduced level, and further modified to comprise and/or express an antigen binding protein e.g., a chimeric antigen receptor (CAR). An improved method of CAR T-cell therapy that comprises administering the improved immune cells, and compositions that comprise the improved immune cells. Methods of improving persistence of administered cells and reducing activation-induced cell death comprising administering the improved cells.