According to Rosenberg SA’s experiences in advanced melanoma, lymphodepletion before TIL cell transfer is essential because it can get rid of regulatory elements (e.g. regulatory T cells or myeloid-derived suppressor cells) in tumor microenvironment and eliminate endogenous lymphocytes that consume homeostatic cytokines like IL-7 and IL-15, which are responsible for sustaining transferred TIL cell survival [26]. The gene discussed is IL15; the disease is neoplasm.