What is the primary cause of febrile non-hemolytic transfusion reactions?

The primary cause of febrile non-hemolytic transfusion reactions is the recipient antibodies reacting against donor white blood cells. During blood transfusion, the transfused leukocytes—particularly white blood cells—can elicit an immune response in the recipient if they have pre-existing antibodies against those leukocytes. This immune response often manifests as a fever due to the release of cytokines and other inflammatory mediators triggered by the interaction between recipient antibodies and donor leukocytes.

This type of reaction is not caused by mismatched blood types, which typically leads to more severe hemolytic reactions rather than febrile ones. Although contamination of blood products can lead to complications and febrile reactions, it is not specifically the primary cause associated with this particular type of transfusion reaction. Similarly, excess iron in donor blood does not directly relate to febrile non-hemolytic transfusion reactions; it is more associated with conditions like iron overload. Therefore, the correct identification of heightened immune response to donor white cells as the cause underscores the importance of screening and possibly reducing leukocyte content in blood transfusions to minimize such reactions.