Defensin, alpha 4 (DEFA4), also known as neutrophil defensin 4 or HNP4, is a human defensin peptide that is encoded by the DEFA4 gene. [3] [4] HNP4 is expressed in the granules of the neutrophil where it defends the host against bacteria [5] and viruses. [6]
Defensins are a peptide family of cytotoxic microbicides involved in innate immunity. [7] Members of the defensin family are distinguished by a conserved six-cysteine motif. Several human alpha defensin genes including HNP4 are clustered on chromosome 8. DEFA4 differs from other defensin genes by an extra 83-base segment that is apparently the result of a recent duplication within the coding region. HNP4 inhibits corticotropin-stimulated corticosterone production. [3]
Defensins are small cysteine-rich cationic proteins across cellular life, including vertebrate and invertebrate animals, plants, and fungi. They are host defense peptides, with members displaying either direct antimicrobial activity, immune signaling activities, or both. They are variously active against bacteria, fungi and many enveloped and nonenveloped viruses. They are typically 18-45 amino acids in length, with three or four highly conserved disulphide bonds.
HLA class II histocompatibility antigen, DR alpha chain is a protein that in humans is encoded by the HLA-DRA gene. HLA-DRA encodes the alpha subunit of HLA-DR. Unlike the alpha chains of other Human MHC class II molecules, the alpha subunit is practically invariable. However it can pair with, in any individual, the beta chain from 3 different DR beta loci, DRB1, and two of any DRB3, DRB4, or DRB5 alleles. Thus there is the potential that any given individual can form 4 different HLA-DR isoforms.
C-X-C motif chemokine 5 is a protein that in humans is encoded by the CXCL5 gene.
Chemokine ligand 7 (CXCL7) is a human gene.
Beta-defensin 2 (BD-2) also known as skin-antimicrobial peptide 1 (SAP1) is a peptide that in humans is encoded by the DEFB4 gene.
Alpha defensins are a family of mammalian defensin peptides of the alpha subfamily. In mammals they are also known as cryptdins and are produced within the small bowel. Cryptdin is a portmanteau of crypt and defensin.
Beta defensins are a family of vertebrate defensins. The beta defensins are antimicrobial peptides implicated in the resistance of epithelial surfaces to microbial colonization.
Defensin, alpha 1 also known as human alpha defensin 1, human neutrophil peptide 1 (HNP-1) or neutrophil defensin 1 is a human protein that is encoded by the DEFA1 gene. Human alpha defensin 1 belongs to the alpha defensin family of antimicrobial peptides.
Beta-defensin 1 is a protein that in humans is encoded by the DEFB1 gene.
Azurocidin also known as cationic antimicrobial protein CAP37 or heparin-binding protein (HBP) is a protein that in humans is encoded by the AZU1 gene.
Beta-defensin 103 is a protein that in humans is encoded by the DEFB103A gene.
Defensin, alpha 5 (DEFA5) also known as human alpha defensin 5 (HD5) is a protein that in humans is encoded by the DEFA5 gene. DEFA5 is expressed in the Paneth cells of the ileum.
Beta-defensin 104 is a protein that in humans is encoded by the DEFB104A gene.
Beta-defensin 106 is a protein that in humans is encoded by the DEFB106A gene.
Beta-defensin 105 is a protein that is encoded by the DEFB105A gene in humans.
Beta-defensin 119 is a protein that in humans is encoded by the DEFB119 gene.
Beta-defensin 129 is a protein that in humans is encoded by the DEFB129 gene.
Defensin, alpha 6 (DEFA6) also known as human alpha defensin 6 (HD6) is a human protein that is encoded by the DEFA6 gene. DEFA6 is expressed in the Paneth cells of the ileum.
Defensin, alpha 3 (DEFA3) also known as human alpha defensin 3, human neutrophil peptide 3 (HNP-3) or neutrophil defensin 3 is a human protein that is encoded by the DEFA3 gene. Human alpha defensin 3 belongs to the alpha defensin family of antimicrobial peptides.
Virtual colony count (VCC) is a kinetic, 96-well microbiological assay originally developed to measure the activity of defensins. It has since been applied to other antimicrobial peptides including LL-37. It utilizes a method of enumerating bacteria called quantitative growth kinetics, which compares the time taken for a bacterial batch culture to reach a threshold optical density with that of a series of calibration curves. The name VCC has also been used to describe the application of quantitative growth kinetics to enumerate bacteria in cell culture infection models. Antimicrobial susceptibility testing (AST) can be done on 96-well plates by diluting the antimicrobial agent at varying concentrations in broth inoculated with bacteria and measuring the minimum inhibitory concentration that results in no growth. However, these methods cannot be used to study some membrane-active antimicrobial peptides, which are inhibited by the broth itself. The virtual colony count procedure takes advantage of this fact by first exposing bacterial cells to the active antimicrobial agent in a low-salt buffer for two hours, then simultaneously inhibiting antimicrobial activity and inducing exponential growth by adding broth. The growth kinetics of surviving cells can then be monitored using a temperature-controlled plate reader. The time taken for each growth curve to reach a threshold change in optical density is then converted into virtual survival values, which serve as a measure of antimicrobial activity.
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