4-1BB signaling can co-stimulate T cells in a CD28-independent manner [37], protect tumor-infiltrating lymphocytes (TILs) from activation-induced cell death (AICD) via upregulation of antiapoptotic pathways [38,39], and enhance cytotoxic T lymphocyte (CTL) survival and cytolytic activity [40]. The gene discussed is CD28; the disease is neoplasm.