Leukodepletion

Leukodepletion, also known as leukoreduction, is the process of removing leukocytes (white blood cells) from blood components or whole blood products. The aim is to reduce adverse transfusion-related reactions, immune sensitization, and the transmission of certain leukocyte-associated pathogens. It is routinely applied to red blood cells and platelets in many healthcare systems and is also used in the preparation of some cellular therapies.

Methods of leukodepletion include prestorage filtration, where leukocytes are removed during collection or processing of blood components; post-storage filtration, which removes leukocytes shortly before issue; and leukocyte reduction by apheresis for certain cellular products. In some settings, filtration is used at the point of care. Irradiation is a separate modality used to prevent transfusion-associated graft-versus-host disease and may be used in conjunction with leukoreduction when indicated.

Indications and effects of leukodepleted products include a reduction in febrile non-hemolytic transfusion reactions, decreased alloimmunization to human leukocyte antigens (HLA), and a lower risk of transmitting certain latent viruses such as cytomegalovirus (CMV) in seronegative recipients. The magnitude of benefit can vary by product and patient population, and evidence supports routine leukoreduction for certain transfusion recipients, though practice standards differ by country and guideline.

Limitations and considerations include residual leukocytes, added cost, and logistical requirements. Leukodepletion is not a substitute for irradiation when there is a risk of transfusion-associated graft-versus-host disease; in those cases irradiation remains essential.