A temperature-dependent inhibitory activity of serum on the capacity of Saccharomyces cerevisiae-derived hepatitis B surface antigen to bind to monocytes.
Hepatitis B surface antigen, when produced in yeast (rHBsAg), is capable of binding to cells that express the lipopolysaccharide coreceptor CD14. This interaction is enhanced by a serum protein, the lipopolysaccharide binding protein (LBP). Here we report that most of the rHBsAg particles that attached to monocytes at 0 degrees C, were not endocytosed but were released back into the serum-containing binding buffer at 37 degrees C. Additionally, serum-dependent binding at 37 degrees C was weak when compared to the serum-dependent attachment at 0 degrees C. Pre-incubation at 37 degrees C of cells together with serum did not abolish binding of freshly added rHBsAg at 0 degrees C. However, pre-incubation of rHBsAg with serum at 37 degrees C reduced attachment to cells following incubation at 0 degrees C. Soluble CD14 and LBP, two serum proteins which can act as phospholipid transfer molecules, were shown not to be responsible for the inhibitory effect. Pre-incubation at 37 degrees C of rHBsAg in serum-free hepatoma cell line-conditioned media resulted in a pronounced reduction in subsequent binding to cells at 0 degrees C. These observations suggest that the temperature-dependent inhibitory effect is caused by serum factors that are probably secreted by hepatocytes.
Center for Vaccinology, Department of Clinical Biology, Microbiology and Immunology, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium. Peter.Vanlandschoot@UGent.be
P
P
Vanlandschoot
F
F
Van Houtte
A
A
Roobrouck
F
F
Stelter
F
F
Gavilanes
G
G
Leroux-Roels
D000209:Acute-Phase Proteins; D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins; D045744:Cell Line, Tumor; D006224:Cricetinae; D017077:Culture Media, Conditioned; D006514:Hepatitis B Surface Antigens / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D006801:Humans; D018950:Lipopolysaccharide Receptors; D008562:Membrane Glycoproteins; D051379:Mice; D009000:Monocytes / Q000276:immunology*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D044967:Serum / Q000276:immunology*; D013696:Temperature; D013997:Time Factors; D000099231:Lipopolysaccharide-Binding Protein
D000209:Acute-Phase Proteins; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D006514:Hepatitis B Surface Antigens; D018950:Lipopolysaccharide Receptors; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D000099231:Lipopolysaccharide-Binding Protein