T-cell transfer is a type of immunotherapy that involves transferring T cells (a type of immune cell) into a patient to help their immune system better recognize and attack cancer cells. This approach is often used in the treatment of certain types of cancer, such as leukemia and lymphoma, where the patient's own immune system is not effectively targeting and destroying the cancer cells. T-cell transfer therapy has shown promising results in clinical trials and is being further developed and studied as a potential cancer treatment option.