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Bactericidal/Permeability-Increasing Protein (BPI) is a cationic glycoprotein stored in azurophilic granules of polymorphonuclear leukocytes (PMNs). Its boomerang-shaped structure features two functional domains: an N-terminal region (residues 1–199) responsible for antimicrobial and endotoxin-neutralizing activities, and a C-terminal domain facilitating opsonization and immune cell interactions. BPI selectively targets Gram-negative bacteria via high-affinity binding (Kd ~2–5 nM) to lipopolysaccharides (LPS), disrupting outer membrane integrity through hydrophobic pocket interactions with lipid A, leading to bacterial permeabilization and death. Additionally, BPI inhibits LPS-induced immune activation by blocking interactions with LPS-binding protein (LBP) and CD14, thereby attenuating cytokine storms.
Clinically, BPI serves as a major autoantigen for anti-neutrophil cytoplasmic antibodies (ANCA) in systemic vasculitis, particularly in patients with chronic Gram-negative infections like cystic fibrosis or inflammatory bowel disease. BPI-ANCA immune complexes induce neutrophil extracellular trap (NET) formation via TNFα-primed neutrophils, exacerbating vascular inflammation and contributing to pauci-immune glomerulonephritis and cutaneous vasculitis. Elevated BPI levels (>45 ng/mL) also correlate with sepsis severity and mortality, serving as a prognostic biomarker.
Common uses include innate immune system studies.
Not a hazardous substance or mixture.
12 - Non Combustible Liquids
