Donor lymphocyte infusion (DLI) is a therapeutic approach primarily utilized in the context of hematopoietic stem cell transplantation (HSCT) to enhance the immune response against residual malignancy, particularly in patients who have experienced relapse after the transplant. This procedure involves the administration of lymphocytes-a type of white blood cell responsible for orchestrating the immune response-collected from a donor, often from the original stem cell donor. The primary purpose of DLI is to reinvigorate the recipient's immune system, facilitating a more effective attack on cancer cells that may remain post-transplant. In many cases, this infusion is particularly beneficial in cases of leukemia or certain types of lymphoma, where post-transplant relapse represents a significant challenge in patient management. The mechanism underlying DLI relies on the recognition of tumor-associated antigens by the infused donor T cells, which can lead to an immune-mediated eradication of the tumor cells-a process referred to as graft-versus-leukemia (GVL) effect. However, this therapeutic strategy is not without risks, as the activation of donor lymphocytes can also lead to the development of graft-versus-host disease (GVHD), a condition where the donor immune cells attack the recipient's healthy tissues. To mitigate this risk, careful patient selection, dosages of the infused cells, and timing of the infusion are critical factors that need to be considered. Typically, patients may receive DLI after a measurable disease relapse or upon signs of impending relapse. The response to DLI can vary considerably among patients, and factors such as the type of hematologic malignancy, the timing of the infusion, and the patient's overall health status play a significant role in determining the efficacy of the treatment. Some patients experience a remarkable response, achieving durable remissions as a result of the infusion, while others may have limited or no response, necessitating alternative therapeutic strategies. Research continues to explore optimizing DLI protocols, including combining DLI with other therapies such as targeted agents, immunotherapies, or increasing the frequency or amount of lymphocyte infusion, which may enhance the overall treatment outcomes. In conclusion, DLI represents a promising and critical option in the post-transplant management of hematologic malignancies, balancing the potential for effective tumor eradication with the risk of adverse immune reactions, and ongoing studies aim to refine and improve its application in clinical practice. Understanding the intricate dynamics of DLI will help in harnessing its full potential, enhancing therapeutic benefits while minimizing potential complications associated with this intricate yet fascinating procedure.
