Table 1 Structure, anti-microbial and immunomodulatory activities of innate immunity proteins and peptides
From: Antimicrobial proteins and polypeptides in pulmonary innate defence
Protein | Structure | pI | Pulmonary Source | Antimicrobial activity | Immunomodulatory activity |
|---|---|---|---|---|---|
Lactoferrin | Iron- binding glycoprotein MW 80 kDa | 8.7 | Neutrophil secondary specific granules and submucosal gland epithelial cells | Bactericidal Bacteriostatic Inhibits biofilm formation Anti-fungal Anti-viral | Binds LPS and can prevent septic shock. Binds CPG motifs. Anti-oxidant. |
SLPI | 11.7 kDA non-glcosylated protein | >9.2 | Macrophages, epithelial cells, neutrophils | Bactericidal Bacteriostatic Anti-viral | Powerful anti-protease Inhibits LPS-induced NF-κB activation. Attenuates pulmonary recruitment of neutrophils in sepsis models. Impairs LTA and LPS induced proinflammatory gene expression in monocytes and macrophages. |
Lysozyme | 14 kDA enzyme | 10.5 | Neutrophil secondary specific granules and submucosal gland epithelial cells | Bactericidal Bacteriostatic | Unknown |
Human Defensins | 3–5 kDA peptides | 8.8–9.5 | Neutrophil azurophil granules and pulmonary epithelial cells | Bactericidal Bacteriostatic Anti-parasitic Anti-fungal Anti-viral | Mitogenic and chemotactic activities. Contribute to epithelial repair in the lung by enhancing epithelial cell proliferation. |
LL-37 | Peptide that requires proteolytic processing to liberate the mature functional antimicrobial peptide. |  | Neutrophil secondary specific granules and submucosal gland epithelial cells | Bactericidal Bacteriostatic Anti-fungal Anti-viral | Reduced production of the pro-inflammatory cytokine TNF-α from macrophages stimulated with LPS and may be responsible for the migration of immune cells to areas of inflammation and infection |
BPI | 55-kDa protein | 9.6 | Neutrophil primary granules | Bactericidal Bacteriostatic Act as an opsonin to enhance neutrophil phagocytosis. | Downregulates LPS and other endotoxins in vivo |
Surfactant proteins A and D | Lipoprotein complex | 4.5–5.4 | Type II pneumocytes, airway Clara cells | Key opsonins facilitating phagocytosis of bactaeria and viruses. Bactericidal Bacteriostatic Anti-fungal Anti-viral | Both SP-A and SP-D have the capacity to modulate multiple leucocyte functions |
Lactoperoxidase | Enzyme | Â | Airway epithelium | Bactericidal Anti-fungal Anti-viral | Â |
CCL20 | Chemokine with similar structure to HBD | Â | Airway epithelium | Bactericidal against Gram negative bacteria | Stimulates the migration of B-cells, immature dendritic cells, and a subset of memory T cells |