Autologous tumor-infiltrating T cells are isolated from the patient’s tumor, expanded ex vivo, and reinfused after lymphodepletion. These unengineered T cells recognize patient-specific tumor antigens via their native TCRs and mediate MHC-restricted cytotoxicity (perforin/granzyme) and cytokine-driven immune responses within the tumor, resulting in direct killing of cancer cells; IL-2 is often provided to support in vivo expansion and persistence.