Defensins

The mechanism of action of defensins is largely unknown. Incubation with defensins results in the formation of voltage-regulated ion channels that permeabilise the outer and inner membranes of metabolically-active E. coli. Because the target bacteria must be metabolically active for defensins to exert their effects, it may be that the transmembrane electromotive force is involved in the mechanism of action. 

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Basic (pH) proteins directed against pathogens. Examples are the major basic protein from mast cells, the eosinophilic cationic proteins from eosinophils, and defensins from epithelial cells and neutrophilic granulocytes. 

Defensins are a group of antimicrobial and cytotoxic peptides made by immune cells. There are seven defensins in humans, six alpha-defensins and one beta-defensin, which are involved in the innate immune defense at the surface of epithelia from the respiratory tract, the intestinal tract or the urinary tract. 

Humoral immunity depends on soluble, noncellular effector mechanisms of the immune system. These include defensins and complement components (proteins of the innate immune system) and antibodies (products of the adaptive immune system). They are capable of reacting with foreign substances (e.g., bacteria and viruses) to produce detoxification and elimination. 

Death Domain and Death Receptors Death Domain Superfamily Defensins... 

Yang D, Chertov O, Bykovskaia SN, et al. Beta-defensins linking innate and adaptive immunity through dendritic and T cell CCR6. Science 1999 286(5439) 525-528. 

Ouellette, A.J. and Selsted, M.E. (1996) Paneth cell defensins endogenous peptide components of intestinal host defense. FASEB Journal 10, 1280-1289. 

Defensins HD 1-6 HBD 1 and 2 Neutrophils (HD1-4) epithelial cells (HBD 1 and 2) macrophages Bacteria, mycobacteria, fungi, and some viruses Cidal activity and chemotaxis Upregulated in the lungs of smokers [36]... 

Ashitani, J., et al., Elevated concentrations of defensins in bronchoalveolar lavage fluid in diffuse panbronchiolitis, Eur. Respir. J. 11, 1, 104, 1998. 

Zhao, C., Wang, I., and Lehrer, R.I., Widespread expression of beta-defensin hBD-1 in human secretory glands and epithelial cells, FEBS. Lett. 396, 2-3, 319, 1996. 

Duits, L.A., et al., Expression of beta-defensin 1 and 2 mRNA by human monocytes, macrophages and dendritic cells, Immunology. 106, 4, 517, 2002. 

Kagan, B.L., et al., Antimicrobial defensin peptides form voltage-dependent ion-permeable channels in planar lipid bilayer membranes, Proc. Natl. Acad. Sci. U. S.A. 87,1,210,1990. 

Goldman, M.J., et al., Human beta-defensin-1 is a salt-sensitive antibiotic in lung that is inactivated in cystic fibrosis, Cell. 88, 4, 553, 1997. 

Kristensen AK, Brunstedt J, Nielsen JE, Mikkelsen JD, Roepsstorff P, Nielsen KK. Processing, disulfide pattern and biological activity of sugar beet defensin AX2, expression in Pichia pastoris. Protein Expr Purif 1999 16 377-387. 

Defense-in-depth concept, for nuclear power plant design, 17 534-536 Defense Logistics Agency (DLA), 14 201 Defensins, 18 258-259... 

Figure 2.9. Amino acid sequences of human defensins. The conserved positions of six cysteine residues are shown in hatched boxes. Abbreviations A, alanine C, cysteine D, aspartic acid E, glutamic acid F, phenylalanine G, glycine H, histidine I, isoleucine K, lysine L, leucine M, methionine N, asparagine P, proline Q, glutamic acid R, arginine S, serine T, threonine V, valine W, tryptophan Y, tyrosine.

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