The immune system plays a key role in Tumor-Infiltrating Lymphocyte (TIL) therapy. Normally, the immune system helps protect the body from infections and abnormal cells, including cancer cells. White blood cells, like T-cells (a type of lymphocyte), are key in identifying and attacking harmful cells. When a tumor grows, it can attract certain types of immune cells to the area. These immune cells, specifically T- cells, can recognize the cancer cells as harmful. However, tumors find ways to hide from or avoid these immune cells, which makes it harder for the immune system to destroy them.

With TIL therapy, doctors remove a tumor lesion with in the body, which contains these immune cells (the TILs) that have already tried to fight the tumor. TILs are usually effective at recognizing cancer cells, but they might need help to become stronger and more active. In a designated TIL manufacturing laboratory, TILs are grown and multiplied in large numbers, sometimes with added growth factors or special treatments that make them more powerful and better able to target the cancer. This process helps increase the number of T-cells that are good at attacking the tumor. During this time, the patient will undergo a short course of lymphodepleting chemotherapy to better prepare their immune system to receive the TIL therapy.

Once the TIL T-cells are ready, they are infused back into the patient. These T-cells now have a greater ability to recognize and attack the cancer cells more effectively. The goal is for the immune system to launch a stronger, more focused attack against the tumor. To further boost the body’s immune response, patients will receive post TIL infusion immunotherapy such as IL-2 an immune checkpoint inhibitor, which may help the immune system to work more effectively against the cancer.