CD4 and neoplasm: Adoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TIL) is a personalized immunotherapy that has been pioneered by Steven A. Rosenberg and colleagues at the National Cancer Institute (NCI).1, 2, 3 TIL-ACT is based on the infusion of autologous CD4+ and CD8+ T lymphocytes that have been collected from tumor material and expanded ex vivo in the presence of interleukin 2 (IL-2).