Which type of blood product undergoes filtration to remove leukocytes?

Leukocyte-reduced units are specifically processed to remove white blood cells (leukocytes) from the blood product. This filtration step is crucial for several reasons, including reducing the risk of febrile non-hemolytic transfusion reactions, minimizing the risk of transmission of certain infections, and preventing immunomodulation.

In contrast, whole blood typically contains all components of blood, including leukocytes, without any processing to remove them. Platelet units are also usually collected with their leukocyte content intact, although some may undergo leukocyte reduction as well. Packed red cells, while primarily consisting of red blood cells, also retain some level of leukocyte content unless specifically treated to ensure that leukocytes are removed. Hence, leukocyte-reduced units are identified as those that have undergone the specific process of filtration to remove those cells, making them the correct answer.