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| Antimicrobial peptide | Chromosomal location | Molecular mass (kDa) | Secretory stimuli | Distribution in gastrointestinal tract | Biological function | Changes in inflammatory bowel disease |
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| hBD-1 | 8p23.1 | 3.5–4.5 | Constitutive in epithelial cells, IFN-γ and LPS in monocytes | Ubiquitous in epithelial cells of small and large intestine, monocytes, monocyte-derived dendritic cells | Antimicrobial, chemotactic | Reduction in colonic IBD |
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| hBD-2, 3, 4 | 8p23.1 | 3.5–4.5 | LPS, flagellin mediated by NF-κB and AP-1 | Epithelial cells, monocytes | - Antimicrobial, chemoattractant for macrophages and monocytes, - hBD-2: mast cells and neutrophils | - Attenuated induction observed in colonic CD- Reduced copy numbers for hBD-2 in colonic CD |
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| HD-5 and HD-6 | 8p23.1 | 3.5–4.5 | NOD2 activation (MDP, LPS) TLR | Granules of ileal Paneth cells (also metaplastic Paneth cells in other areas of intestinal tract) | Antimicrobial, induction of IL-8 | - Reduction in ileal CD, more pronounced in patients with NOD2 mutation- HD-5 and HD-6 expression due to metaplastic Paneth cells in UC and CD colon |
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| Cathelicidin (“LL-37”) | 3p21.3 | 18 | Butyrate, vitamin D, bile acids, MDP | Epithelial cells, leukocytes | Antimicrobial, chemotactic | - Attenuated induction in colonic CD- Ileal CD and UC show regular induction |
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| Elafin | 20q13.12 | 9.8 | IL-1, TNF-α | Epithelial cells, leukocytes | Antiprotease with antimicrobial and chemotactic properties | Attenuated induction in colonic CD |
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| Secretory phospholipase A2 | 16p13.1–p12 | 14 | LPS | Epithelial and inflammatory cells, Paneth cell granules | - Acute phase protein involved in eicosanoide metabolism- Small intestinal mucosal defense | ? |
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| Lysozyme | 12q15 | 16.5 | ? | Gastric, pyloric and duodenal glands, small intestine, macrophages and monocytes, not in colonic tissue | Antimicrobial against Gram-positive bacteria, chemotactic | - Small intestine: no changes observed - Increased colonic expression due to metaplastic Paneth cells |
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| BPI (bactericidal/permeability-increasing protein) | 20q11.23 | 50 | LPS | Epithelial cells, neutrophils | Antimicrobial, binds LPS-compounds | No changes observed, regular induction in IBD |
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