Influence of human transferrin and group-specific protein on endotoxicity in vitro.

The present study concerns the endotoxin neutralizing activity of human iron-free transferrin, and group-specific protein also called Gc-globulin. Iron-free transferrin was used because former studies showed that the endotoxin binding capacity is restricted to apotransferrin. The endotoxin neutralizing activity of the different protein preparations was tested by use of the limulus-amebocyte-lysate test after solubilizing in an isotonic electrolyte buffer at pH 7.0. Surprisingly, in the presence of transferrin the limulus test detected about 200% and 150%, respectively, of the endotoxin content measurable in the presence of human albumin or without any protein. The addition of Gc-globulin leads to a loss of endotoxin of about 40%.