Antimicrobial peptides are present in immune and host defense cells of the human respiratory and gastrointestinal tracts.

Department of Anatomy, Chair II, Ludwig Maximilian University, 80336 München, Germany.
Cell and Tissue Research (Impact Factor: 3.68). 07/2006; 324(3):449-56. DOI: 10.1007/s00441-005-0127-7
Source: PubMed

ABSTRACT Previous studies have implicated antimicrobial peptides in the host defense of the mammalian intestinal and respiratory tract. The aim of the present study has been to characterize further the expression of these molecules in non-epithelial cells of the human pulmonary and digestive systems by detailed immunohistochemical analysis of the small and large bowel and of the large airways and lung parenchyma. Additionally, cells obtained from bronchoalveolar lavage were analyzed by fluorescent activated cell sorting and immunostaining of cytospin preparations. hBD-1, hBD-2, and LL-37 were detected in lymphocytes and macrophages in the large airways, lung parenchyma, duodenum, and colon. Lymphocytes positive for the peptides revealed a staining pattern and distribution that largely matched that of CD3-positive and CD8-positive T-cells. Macrophages with positive staining for the antimicrobial peptides also stained positively for CD68 and CD74. In view of the morphology of the LL-37-positive and hBD-2-positive mucosal lymphocytes, they are probably also B-cells. Thus, antimicrobial peptides of the defensin and cathelicidin families are present in a variety of non-epithelial cells of mucosal organs. These findings confirm that antimicrobial peptides have multiple functions in the biology of the mucosa of these organs.

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Porphyromonas gingivalis trypsin-like proteinase can cleave an intact Ln-332 γ2-chain into smaller fragments and eventually promote the formation of periodontal pockets. hBDs are components of an innate mucosal defense against pathogenic microbes. Our results suggest that P. gingivalis trypsin-like proteinase can degrade hBD and thus reduce the innate immune response. Elevated levels and the increased activity of MMPs have been detected in several pathological tissue-destructive conditions where MMPs are shown to cleave extracellular matrix (ECM) and basement membrane (BM) molecules and to facilitate tissue destruction. Elevated levels of MMP-8 have been reported in many inflammatory diseases. In periodontitis, MMP-8 levels in gingival crevicular fluid (GCF) and in peri-implant sulcular fluid (PISF) are elevated at sites of active inflammation, and the increased levels of MMP-8 are mainly responsible for collagenase activity, which leads to tissue destruction. 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P. gingivalis-induced periodontitis, especially in MMP-8-/- mice, is associated with severe alveolar bone loss and with systemic inflammatory and lipoprotein changes that are likely to be involved in early atherosclerosis. Parodontiitti ja peri-implantiitti ovat kroonisia tulehdussairauksia hampaita ja keinojuuria eli implantteja ympäröivissä kiinnityskudoksissa. Bakteerien aineenvaihduntatuotteet, entsyymit ja toksiinit, sekä isännän oma puolustusvaste vieraille antigeeneille johtavat parodontiitin ja peri-implantiitin taudinkuville tyypilliseen kova- ja pehmytkudosten tuhoutumiseen ja lopulta hampaiden ja implanttien löystymiseen ja irtoamiseen. 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