Donor Lymphocyte Infusion (DLI) is a specialized cellular immunotherapy. It involves collecting lymphocytes from a previous stem cell donor and infusing them into the patient. The primary aim is to enhance the patient’s immune system after an allogeneic stem cell transplant, providing a targeted approach to augment the body’s defenses.
The Purpose of Donor Lymphocyte Infusion
DLI is primarily administered to manage or prevent the recurrence of certain blood cancers, such as chronic myelogenous leukemia (CML), acute myeloid leukemia (AML), or multiple myeloma, following an allogeneic stem cell transplant. It helps re-establish remission by re-engaging the immune system to target remaining malignant cells. DLI is often more effective when dealing with low levels of cancer cells detected early.
DLI can also address other post-transplant challenges. It may help the recipient’s body accept new stem cells, a process known as engraftment, if it is not progressing adequately. Additionally, donor lymphocytes can assist in combating certain viral infections that emerge in the immunocompromised state after a stem cell transplant.
The DLI Process
For the donor, obtaining lymphocytes for DLI involves apheresis. Blood is drawn from a vein, circulated through a machine that separates and collects the lymphocytes, and then the remaining blood components are returned. This collection can occur during the initial stem cell donation or be scheduled separately.
For the patient, receiving DLI is an outpatient procedure. The collected donor lymphocytes are infused intravenously, similar to a blood transfusion. This infusion typically takes less than an hour, allowing patients to return home the same day. Healthcare providers monitor the patient during and after the infusion for any immediate reactions.
The Graft-versus-Leukemia Effect
The therapeutic action of DLI is rooted in a biological phenomenon called the Graft-versus-Leukemia (GVL) effect. When the donor’s lymphocytes are infused into the patient, specific immune cells, particularly T-cells, are introduced. These donor T-cells possess the ability to recognize the patient’s remaining cancer cells as foreign entities. This recognition triggers an immune response where the donor T-cells actively seek out and destroy these malignant cells.
This mechanism is akin to a newly introduced security force identifying and neutralizing hidden threats that the existing system might have overlooked. The donor T-cells specifically target antigens present on the surface of leukemia or myeloma cells, initiating a cascade of immune reactions that lead to the elimination of these cancerous targets. The GVL effect aims to induce or maintain a state of remission in the patient’s cancer. This targeted attack by the donor’s immune cells provides a potent anti-cancer effect without requiring intensive chemotherapy.
Associated Complications
While DLI offers significant therapeutic benefits, it carries potential complications stemming from the powerful immune response it generates. The most notable risk is Graft-versus-Host Disease (GVHD), where the infused donor lymphocytes, in addition to attacking cancer cells, mistakenly identify the patient’s healthy tissues as foreign. This misdirected immune attack can affect various organs, commonly manifesting in the skin (rash), liver (jaundice), and gut (diarrhea or abdominal pain). GVHD can range in severity from mild to severe and requires careful management to mitigate its impact.
Another complication is myelosuppression, which refers to the temporary suppression of the patient’s bone marrow activity. The donor lymphocytes can sometimes affect the patient’s remaining bone marrow cells, leading to a decrease in the production of blood cells. This can result in low blood counts, specifically low white blood cells (increasing infection risk), low red blood cells (leading to anemia), and low platelets (raising the risk of bleeding). Patients receiving DLI are closely monitored with regular blood tests to detect these complications early and allow for prompt intervention.