Objective To study the biological function of p48 by comparing with that of lipopolysaccharide binding protein (LBP).   Methods The ability of p48 to bind lipopolysaccharide (LPS) or lipid A was determined by the experiment of Biosensor and flow cytometry. The biological function of p48 was identified by measuring the secretion of tumor necrosis factor alpha (TNF-α) in human monocyte (U937) or mice. Using the monoclonal antibody (mAb) Fab to NH-LBP

the spatial structure of p48 was assessed by ELISA to determine whether its structure is similar to that of LBP.    Results p48 could accelerate the binding of LPS with peripheral blood mononuclear cells (PBMC)

whos

e ability is about 81% of LBP. p48 could bind LPS or lipid A directly

with the affinity constant of 1.59×10

-6

mol/L or 1.48×10

-6

mol/L respectively. The secretion rate of TNF-α was enhanced by p48

whose effect is about 77% of LBP in vivo or in vitro. That the mAb Fab could bind p48 at high concentration indicated some similar spatial structure between p48 and LBP.   Conclusion p48

similar to LBP in biological function

plays an important role in innate immunity and inflammatory reaction.