INTERACTIONS OF ENDOTOXIN WITH HUMAN BLOOD-CELLS AND SERUM-PROTEINS

Endotoxin interacts with several plasma protein systems and blood cell s, causing release of a multitude of endogenous mediators that contrib ute to the pathophysiological process of sepsis. Binding of I-125-labe lled lipopolysaccharide, LPS, to human blood in vitro showed that the major part of the I-125-LPS was recovered in plasma, whereas only smal l amounts were retained in washed suspensions of granulocytes, erythro cytes, monocytes and lymphocytes, respectively. Whole leukocyte prepar ations or isolated subpopulations incubated with I-125-LPS or fluoresc ein-conjugated LPS followed by autoradiography, Bow cytometry or immun ofluorescence microscopy showed unequivocally that monocytes bound muc h more LPS than did granulocytes and lymphocytes. Lipoprotein electrop horesis followed by autoradiography showed that I-125-LPS bound to all the purified lipoprotein fractions, which was also confirmed by gel f iltration chromatography. These findings demonstrate that monocytes re present the most important blood cell for LPS binding and that radiola belled LPS is able to bind to lipoproteins as well as to other serum c onstituents.