Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock

Saturable CD14-dependent binding of fluorescein-labeled lipopolysaccharide to human monocytes

Abstract

We used rough lipopolysaccharide (ReLPS) to construct a fluorescein labeled LPS (FITC LPS) with a very high labeling efficiency that bound to isolated human monocytes in a CD14 dependent fashion and that in this respect behaved indistinctively from native LPS, The CD14 dependent binding could be inhibited either bg a 1,000 fold excess of unlabeled LPS or by polymyxin B, bactericidal/permeability increasing protein, cationic protein 18, or soluble CD14. Although this FITC LPS preparation no longer possessed the ability to prime neutrophils for the production of reactive oxygen species or to stimulate human monocytes to produce tumor necrosis factor, activation of the Limulus amoebocyte lysate cascade was comparable to activation bg native LPS, Binding to monocytes was enhanced by human pooled serum (HPS) or LPS binding protein (LBP) for LPS concentrations up to 100 ng/ml and was completely CD14 dependent, For LPS concentrations exceeding 100 ng/ml, binding was still partially CD14 dependent, bat not HPS or LBP dependent. CD14 dependent association of LPS with monocytes was shown to be totally saturable, In conclusion, we found an HPS or LBP dependent binding of FITC LPS to monocytes that was CD14 dependent at up to 100 ng of LPS per ml, and saturation of binding was shown.