Review: Defensins and cathelicidins in lung immunity.
Defensins were first identified in 1985 and are now recognized as part of a large family of antimicrobial peptides, divided into three categories: alpha-, beta-, and -defensins. These defensin classes differ in structure, sites of expression and biological activities. Human alpha-defensins include peptides that are expressed primarily in neutrophils, whereas human beta-defensins are widely expressed in epithelial cells, including those lining the respiratory tract. Defensins were first studied for their broad spectrum activity against bacteria, fungi and viruses; however, it is now clear that they also recruit inflammatory cells and promote innate and adaptive immune responses. Recent evidence shows that defensins have anti-inflammatory effects as well. Hence, defensins can participate in all phases of an immune response in the lung, including initial killing of pathogens and mounting - and resolution -- of an immune or inflammatory response. The cathelicidin, LL-37, is an antimicrobial peptide produced by neutrophils and respiratory epithelial cells that has similar roles in lung immunity as the defensins. A major challenge for the coming years will be to sort out the relative contributions of defensins and LL-37 to overall immune responses in the lung and to determine which of their many in vitro activities are most important for lung immunity.
Tecle
Tesfaldet
T
Department of Medicine, Boston University School of Medicine, Massachusetts, USA.
Tripathi
Shweta
S
Hartshorn
Kevan L
KL
D000818:Animals; D000890:Anti-Infective Agents / Q000276:immunology; D054804:Cathelicidins / Q000276:immunology / Q000378:metabolism*; D023082:Defensins / Q000276:immunology / Q000378:metabolism*; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007113:Immunity, Innate; D008168:Lung / Q000473:pathology; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism / Q000473:pathology
D000890:Anti-Infective Agents; D054804:Cathelicidins; D023082:Defensins