Compositions disclosed herein, and methods of use thereof included those for inhibiting or reducing the incidence of cytokine release syndrome or cytokine storm in a subject undergoing CAR T-cell therapy, methods of treating a cancer or tumor, methods of reducing tumor load, methods of reducing the size or growth rate of a cancer or a tumor, and methods of extending of the survival of a subject suffering from a cancer or tumor, wherein the subjects are administered compositions comprising apoptotic cells or apoptotic cell supernatants. Compositions and methods of use thereof may increase the efficacy of a CAR T-cell cancer therapy. Disclosed herein are also compositions and methods of use thereof for decreasing or inhibiting cytokine production in a subject experiencing cytokine release syndrome or cytokine storm. In certain instances compositions may include additional chemotherapeutic or immunomodulatory agents.