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Defensins – innate immunity at the epithelial frontier

Fellermann, Klausa; Stange, Eduard F.b

European Journal of Gastroenterology & Hepatology: July 2001 - Volume 13 - Issue 7 - p 771-776
Review in Depth

Physical barrier function was formerly believed to play the major role in mucosal protection against luminal bacteria. This view has now been challenged by the discovery of specialized molecules that possess antimicrobial activity. More than 100 peptides have been identified so far, and the number is still growing. These peptides are distributed widely and conserved throughout phylogeny. The epithelial expression of antimicrobial peptides is of particular interest as many pathogens adhere to epithelial surfaces and may eventually invade the host. This rapidly acting defence system of innate immunity is already engaged before adoptive immune interactions take place. These antimicrobial peptides consist of constitutive and inducible forms, potentiating this barrier function in terms of an inflammatory response.

One important subgroup of antimicrobial peptides is the family of defensins, which are classified as alpha (α-) and beta (β-) defensins. Eight different peptides with varying antimicrobial properties have been identified. They are distributed widely in humans, and organ-specific expression patterns have been observed. Homologous peptides have been found in other mammals, vertebrates, invertebrates, insects and plants. The identification of α-defensins and their murine counterparts, cryptdins, in the small intestine prompted intensive research into epithelial antimicrobial defence.

aDepartment of Internal Medicine, Division of Gastroenterology, University of Lubeck, Lubeck, and bDepartment of Internal Medicine, Robert Bosch Krankenhaus, Stuttgart, Germany

Correspondence to Klaus Fellermann, Department of Internal Medicine I, Division of Gastroenterology, University of Lubeck, Ratzeburger Allee 160, 23538 Lubeck, Germany Tel: +49 451 500 6255; fax: +49 451 500 3645; e-mail:

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Although the inner and outer surfaces of the human body are colonized by a multitude of pathogens, local or systemic infections occur only rarely. Numerous unspecific defence mechanisms provide an effective barrier that is not broken easily. For example, the skin is protected by the oily keratin layer, and the upper airways exhibit fimbriae with unidirectional transport. A special situation exists in the gastrointestinal tract, particularly in the colon with its massive bacterial load. Factors such as gastric acid, mucus production and propulsive peristalsis limit contact time with the mucosa and possible immune interaction. However, it became clear in the last decade that there are other counteractors to infection: the first to be unravelled was lysozyme. Since then, many other peptides and proteins that mediate defence have been characterized. They have been reviewed extensively [1–5], but their functional roles are just beginning to be elucidated. This review will focus on one family of cationic antimicrobial peptides (CAPs), the defensins, with a special focus on epithelial sites. (For comprehensive reviews, see references [6–9].)

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Genomics and structure

To date, eight different genes have been characterized. They typically have two short exons separated by a large intron. Four neutrophil peptides (HNP-1–4) have a short extra exon that encodes the leading peptide. Based on the organization of three intramolecular disulphide bonds between cysteine residues, they are termed alpha (α-) and beta (β-) defensins. HNP-1–4, human defensin 5 (HD-5) and human defensin 6 (HD-6) constitute the α-defensins. Two β-defensins have been identified: human beta defensin 1 (HBD-1) and human beta defensin 2 (HBD-2). The genomic clustering and their phylogenetic conservation make evolutionary development from one ancestral gene highly likely [10,11]. All known human defensins have been mapped to a locus on chromosome 8 p22-23.1 near the telomere region [11–13]. HBD-1 is located about 100–150 kb apart from HNP-1 [11], and 500–600 kb from HBD-2 [13]. The proposed organization is centromere–HBD-2–HBD-1–HNP–telomere, with the α-defensins HD-5 and HD-6 flanking the myeloic HNPs in a head-to-tail array [10]. So far, polymorphisms have been recognized only in the HBD-1 gene but their importance is unknown [14,15].

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Defensins are cationic, arginine-rich peptides consisting of 28–44 amino acids. The molecular weight varies from 3 to 5 kDa. They all share a typical tertiary structure despite differences in primary structure. Three antiparallel beta sheets are connected by loops, and a beta hairpin with hydrophobic properties protrudes orthogonally [16]. Six cysteine residues form three intramolecular disulphide bonds, which differ among defensins. In α-defensins, these are grouped C1–C6, C2–C4 and C3–C5, whereas in β-defensins, bonds occur between C1–C5, C2–C4 and C3–C6. The molecules are amphiphilic.

Defensins are synthesized as prepropeptides. The prosegment keeps the molecule in an inactive state; recently, matrilysin (MMP-7) was identified as the enzyme responsible for release of the mature defensin in mice [17]. In the human setting, the situation is less clear. HD-5 is stored in its proform in secretory granules of Paneth cells, and is processed to the mature peptide during or after release by cleavage C-terminally to an arginine [18]. Ghosh et al. favour trypsinogen-2 and postulate that activation takes place in the crypt lumen, where this enzyme is abundant [19].

Major isoforms of HD-5 are 32 and 39 amino acids in length, while HD-6 is predominated by its 32-amino-acid form [18]. In urine, several isoforms of HBD-1 with differing antimicrobial activity have been isolated, ranging from 36 to 47 amino acids in length [20]. The predominating isoforms were 40 or 44 amino acids long. For HBD-2, a 41-amino-acid naturally occurring isoform has been identified [21–23].

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Function and biological activities

Defensins have a broad antimicrobial spectrum ranging from Gram-negative to Gram-positive bacteria, mycobacteria, fungi and enveloped viruses. They disrupt microbial cell membranes by binding to the phospholipid-rich, negatively charged moiety, sometimes organized in multimeric complexes [24,25] (reviewed in [6]). However, their precise mode of action remains to be determined. Phagocytotic killing activity of leucocytes is attributed mainly to the high concentration of HNP-1–4. Although high concentrations are also cytotoxic for mammalian cells, lesser amounts promote growth in epithelial cells and fibroblasts [26], suggesting a role in wound-healing processes. Defensins are chemotactic for monocytes, polymorphonuclear leucocytes and T-cells [27–29]. Moreover, they seem to amplify acquired immune responses [30]. HNPs inhibit action of adrenocorticotropic hormone (ACTH) by reversibly binding to the ACTH receptor [31]. The biological function of the latter phenomenon is currently unknown, but diminished cortisol release during stress from infection is a rational explanation.

The in vitro antibacterial activity is in the micromolar range and has been very well characterized in the case of HD-5 [32]. It was effective against Escherichia coli, Listeria monocytogenes, Salmonella typhimurium and Candida albicans. Similar to the HNPs, the activity is inhibited by physiological salt concentrations, but is independent of the pH and is refractory to trypsin digestion. HBD-1 is highly active against Gram-negative bacteria at 100 μg/ml [33]. HBD-2 is 10 times more potent depending on the pathogen tested, but is less effective and bacteriostatic against Gram-positive strains [21].

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The highest density of defensins is found in mammalian granulocytes [34,35]. HNP-1–4 make up about 10% of the total protein and are the most abundant in azurophilic granules mediating phagocytotic microbial killing. Their expression does not seem to be restricted to cells of myeloic origin, as HNPs have also been found in the placenta [36], inflamed colon [37] and saliva [38].

HD-5 and HD-6 are of epithelial origin and abundantly detectable in Paneth cell secretory granules [39–41]. A developmental expression pattern has been observed in the small intestine in accordance with the appearance of Paneth cells, whereas only HD-5 showed a transient colonic expression [42]. Possibly, these defensins may protect stem cells at the crypt base from microbial invasion. Moreover, HD-5 has been found in the female genital tract [43,44] (Table 1).

Table 1

Table 1

The more recent discoveries are the β-defensins. HBD-1 was first isolated from haemofiltrate [45] and HBD-2 from psoriatic scale [21]. Several other epithelial sites of synthesis have now been recognized. Northern blotting was positive for HBD-1 in the kidney and pancreas; other sites were only positive using the more sensitive RT-PCR analysis [46]. Furthermore, HBD-1 has been detected in the kidney, female reproductive tissue [20], salivary gland, pancreas [47], lung [33,48,49], gingival epithelium [50], skin [51] and colon [52] (Table 1). McCray et al. found a developmentally regulated pattern for HBD-1 in the lung, as formerly shown for epithelial α-defensins [48]. HBD-2 was expressed in the trachea, lung, bronchoalveolar lavage (BAL) fluid [22,49,53], skin [13], colon [52] and gingival tissue [23]. Using an RNA library, a broad epithelial distribution throughout many organs has been observed, with the highest amounts in the lung [22] (Table 1).

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Regulation and implications for disease

Little information is available about the regulation of epithelial α-defensins. Several nuclear factor of interleukin 6 (NF-IL 6) and activator protein 2 (AP-2) recognition sequences lie within the 5′-flanking region, implying a response towards pro-inflammatory stimuli [42]. Interestingly, a moderate two- to three-fold induction of defensin mRNA has been encountered in necrotizing enterocolitis paralleled by an increase in Paneth cells [54]. We showed recently that colonic biopsies disclose an up-regulated HD-5 and HD-6 expression in inflammatory bowel disease as well as diverticulitis. The cellular origin is unclear but may be attributable to metaplastic Paneth cells [55]. High interindividual variability of HD-5 and HD-6 expression was observed in the intestine, and increased levels were found in the duodenum in coeliac sprue [56].

HBD-2 is unique among the so far known human defensins, as the gene contains several binding sites for nuclear factor κB (NFκB) and activator protein 1 (AP-1), both involved in transcriptional regulation by pro-inflammatory cytokines, e.g. tumour necrosis factor α (TNFα) and lipopolysaccharide (LPS). These recognition sites are absent in the HBD-1 gene, which is constitutively expressed [46]. However, some regulatory control may still be possible as HBD-1 contains NF-IL 6 and interferon γ (IFNγ) consensus sites [11]. Increased levels of HBD-1 have been detected in urine and plasma in pyelonephritis [57] and in pregnant women [20]. Similar induction to HBD-2 has been observed for bovine homologues of β-defensins, named tracheal antimicrobial peptide (TAP) and lingual antimicrobial peptide (LAP). LPS stimulated epithelial defensin response via the CD14 LPS-receptor, which has been identified on cells of epithelial origin [58,59]. This inducible pattern explains the finding of Liu et al. [13], who discovered HBD-2 only in inflamed skin, and resembles data with LAP in diseased bronchial and intestinal epithelium [60]. In fact, Becker and colleagues [61] have recently identified the activation pathway in tracheobronchial epithelium, where CD14 in conjunction with Toll-receptor mediates an LPS-driven HBD-2 response. Other activation pathways may be possible based on the fact that Gram-positive bacteria and yeasts are also capable of induction. Interestingly, mucoid Pseudomonas strains induce HBD-2, while non-mucoid forms do not [62]. The mechanism may be attributable to pathogen pattern recognition receptors, which identify specific surface determinants.

Another interesting observation is the impaired capacity of airway surface fluid (ASL) to kill microorganisms in cystic fibrosis (CF), which can be restored by reducing the salt concentration. It was postulated that defensins, expressed in respiratory epithelia and present in ASL, are inactivated in the high-salt environment of CF patients, and may account for recurrent pulmonary infections [63]. The relevance of HBD-1 for antimicrobial activity was elegantly shown by using antisense technology in a bronchial xenograft model. Abrogation of HBD-1 message resulted in decreased bacterial killing [33]. Singh et al. reported an increase of HBD-2 peptide in BAL fluid from CF patients and inflammatory lung disease [49]. As stimulated HBD-2 expression of epithelial cells did not differ among CF and non-CF patients, there seems to be no primary defect in defensin production. Moreover, HBD-2 protein is detectable in plasma and greatly increased in bacterial pneumonia [53]. It remains to be determined whether the peptide leaks into the plasma from the epithelial surface. Another inducible epithelial defensin with an interesting distribution pattern has been identified in cattle. Enteric β-defensin (EBD) is expressed in the distal small intestine as well as the colon, and raised levels were found upon infection with Cryptosporidium parvum [64]. No human homologue of this interesting defensin has been identified so far.

HBD-2 is up-regulated by TNFα, interleukin 1β (IL-1β), Gram-negative and to a lesser extent Gram-positive bacteria, and yeasts in keratinocyte cultures [21,49]. Frye et al. observed low levels of gastrointestinal HBD-1 expression, while HBD-2 was absent from uninflamed biopsies [56]. In epithelial cell lines of colonic origin, HBD-1 mRNA and peptide were present, whereas HBD-2 was only found upon interleukin 1α (IL-1α) stimulation or infection with enteroinvasive bacteria [52]. Experiments in a human fetal intestinal xenograft model resembled these in vitro findings of constitutive HBD-1 and inducible HBD-2 expression. We have addressed the question of whether the same occurs in the clinical setting. With RT-PCR analysis and immunohistochemistry, we found a constitutive colonic expression pattern for HBD-1. While the α-defensins were up-regulated in inflammatory bowel disease, including diverticulitis, HBD-2 was apparently a more frequent finding in ulcerative colitis than in Crohn's disease. This is striking as NFκB, a major inductor for HBD-2, is highly elevated in both entities [65,66].

Recent reports claimed that Helicobacter pylori stimulates HBD-2 expression in gastric epithelium in a human gastric epithelial cell line [67,68]. Only type-I strains carrying the cag A pathogenicity island were capable of activation, an event that possibly involved the NFκB pathway [67]. However, this was not specific to Helicobacter as Salmonella species showed the same response [68]. In fact, HBD-2 mRNA expression in the stomach is more often encountered in Helicobacter infection than in Helicobacter-negative cases, strengthening this observation (unpublished observations).

Thus, the available data may be interpreted as follows: organs with an epithelial lining have a unique defensin profile. The α-defensins HD-5 and 6 are to be found in the gastrointestinal tract, especially in the small intestine. HBD-1 is expressed constitutively and may confer a baseline function of host defence in the absence of inflammation. In the case of inflammation, HBD-2 is up-regulated, and the expression of other defensins may extend to other non-specialized cells counteracting the underlying trigger.

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Defensins comprise a new and interesting field of research. They not only confer unspecific defence at the body surface but are in part highly inducible in a specific manner. The induction is rapid in contrast to acquired immunity, and there is an increasing body of evidence suggesting that the aggressor elicits its own specific defensin profile. Further biological activities suggest that defensins link adaptive and innate immunity. Future investigations will address defects in defensin expression possibly causing currently unexplained disorders, such as the inflammatory bowel diseases. Another future focus is new pharmacological interventions enhancing innate defence in infectious diseases.

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Of special interest

••Of outstanding interest

1. Boman HG. Peptide antibiotics and their role in innate immunity. Annu Rev Immunol 1995; 13: 61–92.
2. Boman HG. Peptide antibiotics: holy or heretic grails of innate immunity? Scand J Immunol 1996; 43: 475–482.
3. •Boman HG. Gene-encoded peptide antibiotics and the concept of innate immunity: an update review. Scand J Immunol 1998; 48: 15–25. Last part of a series of most comprehensive reviews of antimicrobial peptides in general.
4. Lehrer RI, Ganz T. Antimicrobial peptides in mammalian and insect host defence. Curr Opin Immunol 1999; 11: 23–27.
5. Schroder JM. Epithelial peptide antibiotics. Biochem Pharmacol 1999; 57: 121–134.
6. Lehrer RI, Lichtenstein AK, Ganz T. Defensins: antimicrobial and cytotoxic peptides of mammalian cells. Annu Rev Immunol 1993; 11: 105–128.
7. Ganz T, Lehrer RI. Defensins. Curr Opin Immunol 1994; 6: 584–589.
8. Diamond G, Bevins CL. Beta-defensins: endogenous antibiotics of the innate host defense response. Clin Immunol Immunopathol 1998; 88: 221–225.
9. Bevins C, Porter EM, Ganz T. Defensins and innate host defence of the gastrointestinal tract. Gut 1999; 45: 911–915.
10. Bevins CL, Jones DE, Dutra A, Schaffzin J, Muenke M. Human enteric defensin genes: chromosomal map position and a model for possible evolutionary relationships. Genomics 1996; 31: 95–106.
11. Liu L, Zhao C, Heng HH, Ganz T. The human beta-defensin-1 and alpha-defensins are encoded by adjacent genes: two peptide families with differing disulfide topology share a common ancestry. Genomics 1997; 43: 316–320.
12. Harder J, Siebert R, Zhang Y, Matthiesen P, Christophers E, Schlegelberger B, Schröder JM. Mapping of the gene encoding human beta-defensin-2 (DEFB2) to chromosome region 8p22-p23.1. Genomics 1997; 46: 472–475.
13. Liu L, Wang L, Jia HP, Zhao C, Heng HHQ, Schutte BC. et al. Structure and mapping of the human beta-defensin HBD-2 gene and its expression at sites of inflammation. Gene 1998; 222: 237–244.
14. Dörk T, Stuhrmann M. Polymorphisms of the human beta-defensin-1 gene. Mol Cell Probes 1998; 12: 171–173.
15. Vatta S, Boniotto M, Bevilacqua E, Belgrano A, Pirulli D, Crovella S, Amoroso A. Human beta defensin 1 gene: six new variants. Hum Mutat 2000; 15: 582–583.
16. Zimmermann GR, Legault P, Selsted ME, Pardi A. Solution structure of bovine neutrophil beta-defensin-12: the peptide fold of the beta-defensins is identical to that of the classical defensins. Biochemistry 1995; 34: 13 663–13 671.
17. Wilson CL, Ouellette AJ, Satchell DP, Ayabe T, Lopez-Boado YS, Stratman JL. et al. Regulation of intestinal α-defensin activation by the metalloproteinase matrilysin in innate host defense. Science 1999; 286: 113–117.
18. ••Porter EM, Poles MA, Lee JS, Naitoh J, Bevins CL, Ganz T. Isolation of human intestinal defensins from ileal neobladder urine. FEBS Lett 1998; 434: 272–276. Elegant attempt to isolate defensins in large scale from small intestine by use of the ileal neobladder.
19. •Ghosh D, Porter EM, Wilk DJ, Poles MA, Ganz T, Bevins CL. Proteolytic cleavage of human intestinal defensin 5 (HD5) precursor by intestinal proteases [Abstract]. Gastroenterology 2000; 118: A839.A839. Studies on HD-5 showing that matrilysin and trypsinogen 2 cleave HD-5 propeptide in vitro. The obtained products match the mature form found in vivo only in the case of trypsinogen 2 digestion. The latter is therefore assumed to be responsible for cleavage in human intestinal crypts.
20. Valore EV, Park CH, Quayle AJ, Wiles KR, McCray PBJ, Ganz T. Human beta-defensin-1: an antimicrobial peptide of urogenital tissues. J Clin Invest 1998; 101: 1633–1642.
21. ••Harder J, Bartels J, Christophers E, Schröder JM. A peptide antibiotic from human skin. Nature 1997; 387: 861.861. First description of inducible HBD-2 isolated from psoriatic scale.
22. •Bals R, Wang X, Wu Z, Freeman T, Bafna V, Zasloff M, Wilson JM. Human beta-defensin 2 is a salt-sensitive peptide antibiotic expressed in human lung. J Clin Invest 1998; 102: 874–880. Broad distribution of HBD-2 expression. Comparative analysis using a customizable RNA library.
23. Mathews M, Jia HP, Guthmiller JM, Losh G, Graham S, Johnson GK. et al. Production of beta-defensin antimicrobial peptides by the oral mucosa and salivary glands. Infect Immun 1999; 67: 2740–2745.
24. Fujii G, Selsted ME, Eisenberg D. Defensins promote fusion and lysis of negatively charged membranes. Protein Sci 1993; 2: 1301–1312.
25. Wimley WC, Selsted ME, White SH. Interactions between human defensins and lipid bilayers: evidence for formation of multimeric pores. Protein Sci 1994; 3: 1362–1373.
26. Murphy CJ, Foster BA, Mannis MJ, Selsted ME, Reid TW. Defensins are mitogenic for epithelial cells and fibroblasts. J Cell Physiol 1993; 155: 408–413.
27. Chertov O, Michiel DF, Xu L, Wang JM, Tani K, Murphy WJ. et al. Identification of defensin-1, defensin-2, and CAP37/azurocidin as T-cell chemoattractant proteins released from interleukin-8-stimulated neutrophils. J Biol Chem 1996; 271: 2935–2940.
28. Yang D, Chertov O, Bykovskaia SN, Chen Q, Buffo MJ, Shogan J. et al. β-defensins: linking innate and adaptive immunity through dendritic and T cell CCR6. Science 1999; 286: 525–528.
29. Yang D, Chen Q, Chertov O, Oppenheim JJ. Human neutrophil defensins selectively chemoattract naive T and immature dendritic cells. J Leukoc Biol 2000; 68: 9–14.
30. Lillard JWJ, Boyaka PN, Chertov O, Oppenheim JJ, McGhee JR. Mechanisms for induction of acquired host immunity by neutrophil peptide defensins. Proc Natl Acad Sci USA 1999; 96: 651–656.
31. Shamova OV, Lesnikova MP, Kokriakov VN, Shkhinek EK, Korneva EA. The action of defensins on the corticosterone level of the blood and on the immune response in stress. Biull Eksp Biol Med 1993; 115: 646–649.
32. •Porter EM, van Dam E, Valore EV, Ganz T. Broad-spectrum antimicrobial activity of human intestinal defensin 5. Infect Immun 1997; 65: 2396–2401. Investigational study of the broad antimicrobial activity of recombinant HD-5.
33. •Goldman MJ, Anderson GM, Stolzenberg ED, Kari UP, Zasloff M, Wilson JM. Human beta-defensin-1 is a salt-sensitive antibiotic in lung that is inactivated in cystic fibrosis. Cell 1997; 88: 553–560. Elegant study with a bronchial xenograft model. Cystic fibrosis xenografts had an increased colonization with pathogens, which was abolished by adenoviral transfer of the CFTR gene. Antimicrobial activity of normal xenografts was ablated upon HBD-1 antisense treatment. It was postulated that HBD-1 is a dominant antimicrobial peptide of the upper airways, which is inactivated by the high-salt environment in cystic fibrosis.
34. Ganz T, Selsted ME, Szklarek D, Harwig SS, Daher K, Bainton DF, Lehrer RI. Defensins: natural peptide antibiotics of human neutrophils. J Clin Invest 1985; 76: 1427–1435.
35. Ganz T, Lehrer RI. Defensins. Pharmacol Ther 1995; 66: 191–205.
36. Svinarich DM, Gomez R, Romero R. Detection of human defensins in the placenta. Am J Reprod Immunol 1997; 38: 252–255.
37. •Cunliffe RN, Rose FRAJ, James PD, Mahida YR. Expression of antimicrobial neutrophil defensin and lysozyme is induced in epithelial cells of active inflammatory bowel disease (IBD) mucosa [Abstract]. Gastroenterology 1999; 116: A286.A286. Detection of human neutrophil peptides in colonic epithelium by immunohistochemistry. Resection samples showed antimicrobial killing.
38. Mizukawa N, Sugiyama K, Fukunaga J, Ueno T, Mishima K, Takagi S, Sugahara T. Defensin-1, a peptide detected in the saliva of oral squamous cell carcinoma patients. Anticancer Res 1998; 18: 4645–4649.
39. •Jones DE, Bevins CL. Paneth cells of the human small intestine express an antimicrobial peptide gene. J Biol Chem 1992; 267: 23 216–23 225. First description of HD-5 in Paneth cells. With a molecular biology approach, HD-5 was detected by in situ hybridization and RT-PCR.
40. •Jones DE, Bevins CL. Defensin-6 mRNA in human Paneth cells: implications for antimicrobial peptides in host defense of the human bowel. FEBS Lett 1993; 315: 187–192. Discovery of HD-6. An antibody is not yet available.
41. ••Porter EM, Liu L, Oren A, Anton PA, Ganz T. Localization of human intestinal defensin 5 in Paneth cell granules. Infect Immun 1997; 65: 2389–2395. Immunohistochemistry and immunogold staining revealed a staining of Paneth cell secretory granules. Moreover, HD-5 was found to be non-toxic to mammalian cells.
42. ••Mallow EB, Harris A, Salzman N, Russell JP, DeBerardinis RJ, Ruchelli E, Bevins CL. Human enteric defensins: gene structure and developmental expression. J Biol Chem 1996; 271: 4038–4045. Promotor analysis of HD-5 and HD-6. Developmental expression was shown to parallel the occurrence of Paneth cells.
43. Svinarich DM, Wolf NA, Gomez R, Gonik B, Romero R. Detection of human defensin 5 in reproductive tissues. Am J Obstet Gynecol 1997; 176: 470–475.
44. Quayle AJ, Porter EM, Nussbaum AA, Wang YM, Brabec C, Yip KP, Mok SC. Gene expression, immunolocalization, and secretion of human defensin-5 in human female reproductive tract. Am J Pathol 1998; 152: 1247–1258.
45. ••Bensch KW, Raida M, Magert HJ, Schulz KP, Forssmann WG. HBD-1: a novel beta-defensin from human plasma. FEBS Lett 1995; 368: 331–335. Isolation of HBD-1 from haemofiltrate; concentration in plasma was in the nanomolar range.
46. ••Zhao C, Wang I, Lehrer RI. Widespread expression of beta-defensin hBD-1 in human secretory glands and epithelial cells. FEBS Lett 1996; 396: 319–322. HBD-1 was detected in various tissues by RT-PCR. Cell culture studies revealed a constitutive expression pattern.
47. Schnapp D, Reid CJ, Harris A. Localization of expression of human beta defensin-1 in the pancreas and kidney. J Pathol 1998; 186: 99–103.
48. McCray PBJ, Bentley L. Human airway epithelia express a beta-defensin. Am J Respir Cell Mol Biol 1997; 16: 343–349.
49. Singh PK, Jia HP, Wiles K, Hesselberth J, Liu L, Conway BA. et al. Production of beta-defensins by human airway epithelia. Proc Natl Acad Sci USA 1998; 95: 14 961–14 966.
50. Krisanaprakornkit S, Weinberg A, Perez CN, Dale BA. Expression of the peptide antibiotic human beta-defensin 1 in cultured gingival epithelial cells and gingival tissue. Infect Immun 1998; 66: 4222–4228.
51. Fulton C, Anderson GM, Zasloff M, Bull R, Quinn AG. Expression of natural peptide antibiotics in human skin. Lancet 1997; 350: 1750–1751.
52. ••O'Neil DA, Porter EM, Elewaut D, Anderson GM, Eckmann L, Ganz T, Kagnoff MF. Expression and regulation of the human β-defensins hBD-1 and hBD-2 in intestinal epithelium. J Immunol 1999; 163: 6718–6724. Constitutive HBD-1 and inducible HBD-2 expression were found in an intestinal cell line. Enteroinvasive bacteria and IL-1 up-regulated HBD-2 expression. Blocking of NFκB activation resulted in an abrogation of the HBD-2 response. The same expression pattern was present in a human fetal intestinal xenograft model where intraluminal Salmonella induced HBD-2.
53. •Hiratsuka T, Nakazato M, Date Y, Ashitani J, Minematsu T, Chino N, Matsukura S. Identification of human beta-defensin-2 in respiratory tract and plasma and its increase in bacterial pneumonia. Biochem Biophys Res Commun 1998; 249: 943–947. Sensitive radioimmunoassay for HBD-2.
54. •Salzman NH, Polin RA, Harris MC, Ruchelli E, Hebra A, Zirin BS. et al. Enteric defensin expression in necrotizing enterocolitis. Pediatr Res 1998; 44: 20–26. Enterocolitis with an up-regulated HD-5 and HD-6 expression paralleled by increased number of Paneth cells.
55. Symonds DA. Paneth cell metaplasia in diseases of the colon and rectum. Arch Pathol 1974; 97: 343–347.
56. Frye M, Bargon J, Lembcke B, Wagner TOF, Gross V. Differential expression of human α- and β-defensins mRNA in gastrointestinal epithelia. Eur J Clin Invest 2000; 30: 695–701.
57. Hiratsuka T, Nakazato M, Ihi T, Minematsu T, Chino N, Nakanishi T. et al. Structural analysis of human β-defensin-1 and its significance in urinary tract infection. Nephron 2000; 85: 34–40.
58. Diamond G, Russell JP, Bevins CL. Inducible expression of an antibiotic peptide gene in lipopolysaccharide-challenged tracheal epithelial cells. Proc Natl Acad Sci USA 1996; 93: 5156–5160.
59. Russell JP, Diamond G, Tarver AP, Scanlin TF, Bevins CL. Coordinate induction of two antibiotic genes in tracheal epithelial cells exposed to the inflammatory mediators lipopolysaccharide and tumor necrosis factor alpha. Infect Immun 1996; 64: 1565–1568.
60. Stolzenberg ED, Anderson GM, Ackermann MR, Whitlock RH, Zasloff M. Epithelial antibiotic induced in states of disease. Proc Natl Acad Sci USA 1997; 94: 8686–8690.
61. Becker MN, Diamond G, Verghese MW, Randell SH. CD14-dependent lipopolysaccharide-induced beta-defensin-2 expression in human tracheobronchial epithelium. J Biol Chem 2000; 275: 29 731–29 736.
62. Harder J, Meyer-Hoffert U, Teran LM, Schwichtenberg L, Bartels J, Maune S, Schroder JM. Mucoid Pseudomonas aeruginosa, TNF-alpha, and IL-1beta, but not IL-6, induce human beta-defensin-2 in respiratory epithelia. Am J Respir Cell Mol Biol 2000; 22: 714–721.
63. ••Smith JJ, Travis SM, Greenberg EP, Welsh MJ. Cystic fibrosis airway epithelia fail to kill bacteria because of abnormal airway surface fluid. Cell 1996; 85: 229–236. Airway surface fluid from normal and CF epithelia was antimicrobial active while only epithelia from non-CF patients killed the pathogen. Antimicrobial activity of CF epithelia was reconstituted by reduction of the elevated sodium chloride concentration.
64. Tarver AP, Clark DP, Diamond G, Russell JP, Erdjument BH, Tempst P. et al. Enteric beta-defensin: molecular cloning and characterization of a gene with inducible intestinal epithelial cell expression associated with Cryptosporidium parvum infection. Infect Immun 1998; 66: 1045–1056.
65. Schreiber S, Nikolaus S, Hampe J. Activation of nuclear factor κB in inflammatory bowel disease. Gut 1998; 42: 477–484.
66. Rogler G, Brand K, Vogl D, Page S, Hofmeister R, Andus T. et al. Nuclear factor κB is activated in macrophages and epithelial cells of inflamed intestinal mucosa. Gastroenterology 1998; 115: 357–369.
67. Wada A, Mori T, Oishi K, Hojo H, Nakahara Y, Hamanaka Y. et al. Induction of human β-defensin-2 mRNA expression by Helicobacter pylori in human gastric cell line MKN45 cells on cag pathogenicity island. Biochem Biophys Res Commun 1999; 263: 770–774.
68. O'Neil DA, Cole SP, Martin-Porter E, Housley MP, Liu L, Ganz T, Kagnoff MF. Regulation of human beta-defensins by gastric epithelial cells in response to infection with Helicobacter pylori or stimulation with interleukin-1. Infect Immun 2000; 68: 5412–5415.
69. Abiko Y, Mitamura J, Nishimura M, Muramatsu T, Inoue T, Shimono M, Kaku T. Pattern of expression of beta-defensins in oral squamous cell carcinoma. Cancer Lett 1999; 143: 37–43.
    70. Lee SH, Lim HH, Lee HM, Choi JO. Expression of human beta-defensin 1 mRNA in human nasal mucosa. Acta Otolaryngol (Stockh) 2000; 120: 58–61.
      71. Krisanaprakornkit S, Kimball JR, Weinberg A, Darveau RP, Bainbridge BW, Dale BA. Inducible expression of human beta-defensin 2 by Fusobacterium nucleatum in oral epithelial cells: multiple signaling pathways and role of commensal bacteria in innate immunity and the epithelial barrier. Infect Immun 2000; 68: 2907–2915.
        72. Mizukawa N, Sawaki K, Yamachika E, Fukunaga J, Ueno T, Takagi S, Sugahara T. Presence of human beta-defensin-2 in oral squamous cell carcinoma. Anticancer Res 2000; 20: 2005–2007.
          73. Schnapp D, Harris A. Antibacterial peptides in bronchoalveolar lavage fluid. Am J Respir Cell Mol Biol 1998; 19: 352–356.
            74. Bonass WA, High AS, Owen PJ, Devine DA. Expression of beta-defensin genes by human salivary glands. Oral Microbiol Immunol 1999; 14: 371–374.
              75. Cunliffe RN, Rose FRAJ, Keyte J, Abberley L, Chan WC, Mahida YR. Isolation and characterisation of human defensin 5 (HD5) from small intestinal Paneth cells [Abstract]. Gut 1999; 45: A27.A27.
                76. Milner SM, Ortega MR. Reduced antimicrobial peptide expression in human burn wounds. Burns 1999; 25: 411–413.
                  77. Haynes RJ, Tighe PJ, Dua HS. Antimicrobial defensin peptides of the human ocular surface. Br J Ophthalmol 1999; 83: 737–741.
                    78. Haynes RJ, McElveen JE, Dua HS, Tighe PJ, Liversidge J. Expression of human beta-defensins in intraocular tissues. Invest Ophthalmol Vis Sci 2000; 41: 3026–3031.
                      79. Lehmann OJ, Hussain IR, Watt PJ. Investigation of beta defensin gene expression in the ocular anterior segment by semiquantitative RT-PCR. Br J Ophthalmol 2000; 84: 523–526.
                        80. McNamara NA, Van R, Tuchin OS, Fleiszig SM. Ocular surface epithelia express mRNA for human beta defensin-2. Exp Eye Res 1999; 69: 483–490.
                          81. Zucht HD, Grabowsky J, Schrader M, Liepke C, Jurgens M, Schulz KP, Forssmann WG. Human beta-defensin-1: a urinary peptide present in variant molecular forms and its putative functional implication. Eur J Med Res 1998; 3: 315–323.
                            82. Tunzi CR, Harper PA, Bar-Oz B, Valore EV, Semple JL, Watson-MacDonell J. et al. Beta-defensin expression in human mammary gland epithelia. Pediatr Res 2000; 48: 30–35.

                              antimicrobial peptide; defensin; epithelial cell; innate immunity

                              © 2001 Lippincott Williams & Wilkins, Inc.