Defensins in innate immunity

Abstract

The innate immune system is the first line of defense against many common microorganisms, which can initiate adaptive immune responses to provide increased protection against subsequent re-infection by the same pathogen. As a major family of antimicrobial peptides, defensins are widely expressed in a variety of epithelial cells and sometimes in leukocytes, playing an important role in the innate immune system due to their antimicrobial, chemotactic and regulatory activities. This review introduces their structure, classification, distribution, synthesis, and focuses on their biological activities and mechanisms, as well as clinical relevance. These studies of defensins in the innate immune system have implications for the prevention and treatment of a variety of infectious diseases, including bacterial ocular disease.

Three-dimensional NMR Structure of Hen Egg Gallin (Chicken Ovodefensin) Reveals a New Variation of the β-Defensin Fold

“…Root mean square deviations testify that the three-dimensional structure is very well defined with a pairwise root mean square deviation on the C␣ atoms of 0.47Å, and calculated energies are totally satisfactory (Table 2). (47,48), such as defensins or such as host defense peptides in general, it could be particularly instructive to explore whether a priori unrelated proteins, with very low sequence identity, could match with the protein of interest. Structural databanks were explored to determine if other proteins adopt the five-stranded ␤-sheet fold described for gallin.…”

Defensins: Potential Effectors in Autoimmune Rheumatic Disorders

“…Across species, over 800 distinct molecules have been included into this group [3,4]. Amongst them, the family of defensins have been identified in nearly all species from plants over insects to higher mammals [2].…”

“…Human α-defensin 1-4 (commonly referred to as human neutrophil peptides (HNP)) are the major protein species within azurophilic granules of neutrophils, comprising up to 70% of their content [8], while human defensins (hD) 5 and 6 are almost exclusively found in paneth cells of the small intestine [7,9]. Human β-defensins (hBD) are predominantly expressed at epithelial surfaces, but hBD1-4 were also detected in various blood-cells such as monocytes, macrophages and dendritic cells [2,3]. While hBD1 seems to be a constitutively expressed defensin, most other defensins are consistently upregulated by proinflammatory stimuli such as lipopolysaccharides, tumor necrosis factor α (TNFα), and Interleukin-1b (IL1β) [2].…”

“…While hBD1 seems to be a constitutively expressed defensin, most other defensins are consistently upregulated by proinflammatory stimuli such as lipopolysaccharides, tumor necrosis factor α (TNFα), and Interleukin-1b (IL1β) [2]. Signal transduction mechanisms were reported to predominantly depend upon nuclear factor κB [3]. All defensins exert antimicrobial effects against a wide range of pathogens including bacteria, fungi, viruses and parasites [3,4].…”

“…Signal transduction mechanisms were reported to predominantly depend upon nuclear factor κB [3]. All defensins exert antimicrobial effects against a wide range of pathogens including bacteria, fungi, viruses and parasites [3,4]. Their positive charge facilitates association to membranes followed by the generation of pores that disrupt electrolyte homeostasis, thereby leading to cell death [4].…”