BPI (bactericidal/permeability-increasing protein) is a 55 kDa cationic antimicrobial protein primarily expressed in neutrophil azurophilic granules 1, with additional expression by mucosal epithelia and dermal fibroblasts 2. BPI's primary function is selective defense against Gram-negative bacteria through three complementary mechanisms: direct bactericidal activity, opsonization of bacteria for enhanced clearance, and potent endotoxin (LPS) neutralization 1. The protein's Gram-negative specificity results from its highly basic N-terminal domain's strong affinity for negatively charged lipopolysaccharides unique to Gram-negative outer membranes 3. BPI also exhibits anti-inflammatory properties by suppressing TNF-α, IL-6, and IL-8 production and reducing macrophage activation 2. Clinically, elevated plasma BPI correlates with sepsis severity and organ dysfunction 4, and BPI serves as a potential biomarker for disease activity in inflammatory conditions 5. Auto-antibodies against BPI are associated with chr20 Pseudomonas aeruginosa infection and compromise innate immunity 1, suggesting pathogenic autoimmunity. BPI homologs are under biopharmaceutical development as novel anti-infective agents 6, with therapeutic potential in sepsis and inflammatory bowel disease 57.