Lipids accumulate during the storage of red blood cells (RBCs), prime neutrophils (PMNs), and have been implicated in transfusion-related acute lung injury (TRALI). These lipids are composed of two classes: nonpolar lipids and lysophosphatidylcholines based on their retention time on separation by high-pressure liquid chromatography. Prestorage leukoreduction significantly decreases white blood cell and platelet contamination of RBCs; therefore, it is hypothesized that prestorage leukoreduction changes the classes of lipids that accumulate during storage, and these lipids prime PMNs and induce acute lung injury (ALI) as the second event in a two-event in vivo model.
STUDY DESIGN AND METHODS
RBC units were divided: 50% was leukoreduced (LR-RBCs), stored, and sampled on Day 1 and at the end of storage, Day 42. Priming activity was evaluated on isolated PMNs, and the purified lipids from Day 1 or Day 42 were used as the second event in the in vivo model.
The plasma and lipids from RBCs and LR-RBCs primed PMNs, and the LR-RBC activity decreased with longer storage. Unlike RBCs, nonpolar lipids comprised the PMN-priming activity from stored LR-RBCs. Mass spectroscopy identified these lipids as arachidonic acid and 5-, 12-, and 15-hydroxyeicsotetranoic acid. At concentrations from Day 42, but not Day 1, three of four of these lipids individually, and the mixture, primed PMNs. The mixture also caused ALI as the second event in a two-event model of TRALI.
We conclude that the nonpolar lipids that accumulate during LR-RBC storage may represent the agents responsible for antibody-negative TRALI.