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Chapter 2 : Defensins and Other Antimicrobial Peptides: Innate Defense of Mucosal Surfaces
Category: Clinical Microbiology; Bacterial Pathogenesis
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This chapter provides an in-depth account of defensins, and ties together the roles of other antimicrobial peptides and proteins that together contribute to mucosal innate host defense. While the focus is on defensins and antimicrobial peptides from humans, peptides from other species are also included where appropriate. The structural and functional relationships between these three classes of alpha-defensins, beta-defensins, theta-defensins are discussed in this chapter. The antibacterial and antifungal activities of the resulting retrocyclin were modest and were similar to those of synthetic and native rhesus theta-defensins. The noticeable salt sensitivity of ELR- CXC chemokines was similar to that of defensins and many other antimicrobial peptides. High concentrations of alpha-defensins are frequently observed in chronically inflamed tissues. Certain factors within airway fluid, including electrolytes and anionic macromolecules, decrease the activity of many antimicrobial peptides, including defensins. Even though the processing of human neutrophil alpha-defensins occurs during neutrophil maturation prior to cellular release from the bone marrow, matrilysin may participate in the activation of beta-defensins or other antimicrobial peptides in the human airways. Defensins and other antimicrobial peptides and proteins coat mucosal surfaces and are among the primary early mediators of host defense against colonization and tissue invasion by pathogenic microbes. In vitro and in vivo studies indicate that most antimicrobial peptides probably act as endogenous antibiotics.