What is the primary cause of Transfusion Related Acute Lung Injury?

Transfusion Related Acute Lung Injury (TRALI) is a serious complication that can occur after blood transfusions, primarily characterized by acute respiratory distress. The primary cause of TRALI is the presence of leukocyte antibodies in the donor plasma, which can react with the recipient's leukocytes. This immunologic reaction leads to the activation of the recipient's immune system, resulting in neutrophil activation and subsequent pulmonary capillary injury. This process can cause the pulmonary edema and respiratory symptoms that define TRALI.

The other options do not primarily drive the pathophysiology of TRALI. Plasma proteins, while they can play a role in various transfusion reactions, are not the main trigger for TRALI. Iron overload typically relates to repeated transfusions and can cause a different set of complications, mainly affecting organ systems rather than acute lung injury. Platelet discrepancies can lead to issues like transfusion reactions or thrombocytopenia but are not directly tied to TRALI’s mechanism. Thus, the presence of leukocyte antibodies is critical in understanding the etiology of TRALI, making it the correct answer.