Adoptive cell transfer

Adoptive cell transfer (ACT) is the transfer of cells into a patient. The cells may have originated from the patient or from another individual. The cells are most commonly derived from the immune system with the goal of improving immune functionality and characteristics. In autologous cancer immunotherapy, T cells are extracted from the patient, genetically modified and cultured in vitro and returned to the same patient. Comparatively, allogeneic therapies involve cells isolated and expanded from a donor separate from the patient receiving the cells. Adoptive cell transfer (ACT) is the transfer of cells into a patient. The cells may have originated from the patient or from another individual. The cells are most commonly derived from the immune system with the goal of improving immune functionality and characteristics. In autologous cancer immunotherapy, T cells are extracted from the patient, genetically modified and cultured in vitro and returned to the same patient. Comparatively, allogeneic therapies involve cells isolated and expanded from a donor separate from the patient receiving the cells. In the 1960s, lymphocytes were discovered to be the mediators of allograft rejection in animals. Attempts to use T cells to treat transplanted murine tumors required cultivating and manipulating T cells in culture. Syngeneic lymphocytes were transferred from rodents heavily immunized against the tumor to inhibit growth of small established tumors, becoming the first example of ACT. Description of T cell growth factor interleukin-2 (IL-2) in 1976 allowed T lymphocytes to be grown in vitro, often without loss of effector functions. High doses of IL-2 could inhibit tumor growth in mice. 1982, studies demonstrated that intravenous immune lymphocytes could treat bulky subcutaneous FBL3 lymphomas. Administration of IL-2 after cell transfer enhanced therapeutic potential. In 1985 IL-2 administration produced durable tumor regressions in some patients with metastatic melanoma. Lymphocytes infiltrating the stroma of growing, transplantable tumors provided a concentrated source of tumor-infiltrating lymphocytes (TIL) and could stimulate regression of established lung and liver tumors. In 1986, human TILs from resected melanomas were found to contain cells that could recognize autologous tumors. In 1988 autologous TILs were shown to reduce metastatic melanoma tumors. Tumor-derived TILs are generally mixtures of CD8+ and CD4+ T cells with few major contaminating cells. In 1989 Zelig Eshhar published the first study in which a T cell’s targeting receptor was replaced, and noted that this could be used to direct T cells to attack any kind of cell; this is the essential biotechnology underlying CAR-T therapy. Responses were often of short duration and faded days after administration. In 2002, lymphodepletion using a nonmyeloablative chemotherapy regimen administered immediately before TIL transfer increased cancer regression, as well as the persistent oligoclonal repopulation of the host with the transferred lymphocytes. In some patients, the administered antitumor cells represented up to 80% of the CD8+ T cells months after the infusion. Initially, melanoma was the only cancer that reproducibly yielded useful TIL cultures. In 2006 administration of normal circulating lymphocytes transduced with a retrovirus encoding a T-cell receptor (TCR) that recognized the MART-1 melanoma-melanocyte antigen, mediated tumor regression. In 2010 administration of lymphocytes genetically engineered to express a chimeric antibody receptor (CAR) against B cell antigen CD19 was shown to mediate regression of an advanced B cell lymphoma. In 2009, a woman given T cells engineered to recognize colon cancer went into respiratory distress and died. By 2010, doctors had begun experimental treatments for leukemia patients using CD19-targeted T cells with added DNA to stimulate cell division. As of 2015 trials had treated about 350 leukemia and lymphoma patients. Antigen CD19 appears only on B cells, which go awry in lymphoma and leukemia. Loss of B cells can be countered with immunoglobulin.