Bactericidal permeability-increasing protein, bactericidal/permeability-increasing protein, BPI, CAP 57, BPI_HUMAN.
The antimicrobial protein Bactericidal Permeability Increasing protein (BPI) is a 55 kDa protein found in the primary granules of polymorhonuclear leukocytes (PMN). The cytotoxicity action of BPI is limited to gram negative bacteria, reflecting the high affinity of BPI for bacterial LPS. Binding of BPI to live bacteria via LPS causes anti-infective activites: 1) cytotoxicity via sequential damage to bacterial outer and inner lipid membranes, 2) neutralization of gram-negative bacterial LPS, 3) opsonization of bacteria to enhance phagocytosis by neutrophils.
