 Bactericidal permeability-increasing protein (BPI) is a potent antimicrobial protein of 456 amino acids that binds to and neutralises lipopolysaccharides from the outer membrane of Gram-negative bacteria.BPI contains two domains that adopt the same structural fold, even though they have little sequence similarity.Lipopolysaccharide-binding protein (LBP) is an endotoxin-binding protein that is closely related to, and functions in a co-ordinated manner with BPI to facilitate an integrated host response to invading Gram-negative bacteria.