Bactericidal Proteins in Host Defense Against Gram-Negative Bacteria
Summary
Host defence against Gram-negative bacteria relies on a repertoire of specialised proteins capable of direct microbial killing, neutralisation of endotoxin and enhancement of phagocytic clearance. Chief among these is bactericidal/permeability-increasing protein (BPI), a cationic molecule stored in neutrophil and macrophage granules that binds lipopolysaccharide (LPS) on bacterial membranes, disrupts outer membrane integrity and prevents LPS-mediated hyperinflammation. Complementing BPI activity, host-derived antimicrobial peptides such as defensins and cathelicidins insert into bacterial membranes to induce rapid permeabilisation. Other soluble factors, including complement components and collectins, opsonise bacteria to promote recognition by professional phagocytes. Emerging studies highlight synergy between these systems: BPI not only exerts cytotoxic effects but also acts as an opsonin, bridging bacteria to integrin receptors on neutrophils for enhanced uptake. In parallel, acute-phase proteins and lipoprotein-binding modules fine-tune the inflammatory response, clearing bacteria while preventing host tissue damage. Collectively, bactericidal proteins form a multilayered defence that is increasingly recognised as a source of novel antimicrobial strategies, especially in the face of rising antibiotic resistance.
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Bactericidal Proteins in Host Defense Against Gram-Negative Bacteria publication trend
The graph below shows the total number of articles in bactericidal proteins in host defense against gram-negative bacteria across all publications each year (not limited to Nature Index journals).
Technical terms
Bactericidal/permeability-increasing protein (BPI): A cationic granule protein that binds bacterial LPS, disrupts Gram-negative outer membranes and neutralises endotoxin.
Lipopolysaccharide (LPS): A glycolipid component of the outer membrane of Gram-negative bacteria that triggers potent innate immune responses.
Opsonic activity: The process by which host proteins coat pathogens to enhance recognition and uptake by phagocytes.
Phagocytosis: The cellular mechanism by which immune cells internalise and destroy microbes.
Antimicrobial peptide: A small, often cationic, peptide that disrupts microbial membranes and modulates immune responses.
References
- Bactericidal/Permeability-Increasing Protein (BPI), a Novel Antimicrobial Molecule in Human Breast Milk with Immune Potential. Microorganisms (2025).
- Bactericidal/Permeability-Increasing Protein Preeminently Mediates Clearance of Pseudomonas aeruginosa In Vivo via CD18-Dependent Phagocytosis. Frontiers in Immunology (2021).
- Bactericidal Permeability Increasing Protein Deficiency Aggravates Acute Colitis in Mice by Increasing the Serum Levels of Lipopolysaccharide. Frontiers in Immunology (2021).
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