Evidence for endotoxin binding capacity of human Gc-globulin and transferrin

In the present paper the ability of Gc-globulin and transferrin to bind endotoxin of Escherichia coli 0 111: B 4 is demonstrated. This conclusion is based on four lines of evidence. By affinity chromatography using lipopolysaccharide of E. coli 0 111: B 4 two endotoxin-binding proteins of serum were identified, showing an apparent molecular weight of 77,000 and 51,000, respectively. If serum samples preincubated with the tritiated endotoxin form have undergone isoelectric focusing under non-denaturing conditions one radioactive peak appears which coincides with the precipitate obtained by immunoelectrophoresis against anti-human Gc-globulin and anti-human transferrin. Radioimmunoprecipitation experiments of serum showed that tritiated endotoxin of E. coli 0 111: B 4 was only found in the precipitate obtained with anti-Gc-globulin, antitransferrin, and polyvalent antiserum against human serum. By isoelectric focusing of purified proteins 3H-lipopolysaccharide of E. coli 0 111: B 4 was only found associated with human Gc-globulin and transferrin.