Complement Activation by Liposome-Encapsulated Hemoblobin in Vitro: The Role of Endotoxin Contamination.

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