Complement Activation by Liposome-Encapsulated Hemoglobin In Vitro: The Role of Endotoxin Contamination

Abstract

Incubation of liposome-encapsulated Hb (LEH) with rat serum at 37°C led to accelerated decay of serum hemolytic complement (C) activity (CH₅₀/ml). Empty liposomes (L) caused less decrease of CH₅₀/ml, whereas free Hb had no effect on C activity. The LEH- and L-induced increases in C consumption were unlikely a consequence of endotoxin (LPS) contamination, as spiking of rat serum with LPS caused reduction in C only at levels significantly higher than those detectable in LEH or L. LPS-induced C consumption was not potentiated by free hemoglobin.