Background: Recurrent acute tonsillitis is one of the most frequent ENT referrals, yet its pathogenesis remains poorly understood, and tonsillectomy still costs the National Health Service more than £60 000 000 annually. Antimicrobial cationic peptides are components of the innate immune system. They are generally small, highly positively charged peptides with broad spectrum antimicrobial activity which function as the body's ‘natural antibiotics'. The role of antimicrobial cationic peptides in the susceptibility of patients to recurrent acute tonsillitis is unknown.
"In the airways, the epithelium provides a barrier to entry of pathogens through tight junctions and mucociliary functions, but also through the production of antimicrobial peptides (AMPs) (Ball et al., 2007; Schwaab et al., 2009, 2010 Tieu et al., 2010). Their mechanisms of action include a variable degree of antimicrobial activity against bacteria, fungi, and some enveloped viruses (Bals et al., 1998). "
[Show abstract][Hide abstract] ABSTRACT: Airway infections are known to cause exacerbations of allergy and asthma. Tonsils constitute a primary site for microbial recognition and triggering of the immune system in the airways. Human β-defensins (HBDs) are antimicrobial peptides with an important role in this defense. Our aim was to investigate HBD1-3 in tonsillar tissue and their potential role in allergic rhinitis (AR). Tonsils, obtained from patients with AR and non-allergic controls, and isolated tonsillar CD4(+), CD8(+) and CD19(+) lymphocytes were analyzed for HBD1-3 expression using real-time RT-PCR and/or immunohistochemistry. Tonsillar tissue, mixed tonsillar lymphocytes and airway epithelial cells (AECs) were cultured with or without IL-4, IL-5, IL-13 or histamine followed by measurements of HBD1-3 release using ELISA. HBD1-3 were present in tonsillar tissue, including epithelial, CD4(+), CD8(+) and CD19(+) cells. The expression was reduced in allergic compared to healthy tonsils. Stimulation of AECs with IL-4, IL-5 and histamine down-regulated the HBD release, whereas no effects were seen in cultured tonsils or lymphocytes. This study demonstrates presence of HBD1-3 in tonsils and that the levels are reduced in patients with AR. Together with the down-regulation of HBDs in epithelial cells in the presence of allergic mediators suggest that AR patients have an impaired antimicrobial defense that might make them more susceptible to respiratory tract infections.
"Our data also contrast with those of Ball et al.  which is likely due to a difference in the antibody used and the methodology selected. We concluded that the antibody used herein is specific for LL-37, especially as this LL-37 staining was entirely blocked by overnight pre-incubation of the antibody with LL-37 peptide (Fig. 4g). "
[Show abstract][Hide abstract] ABSTRACT: Antimicrobial peptides are essential elements of epithelial defense against invading micro-organisms. The palatine tonsils are positioned at the entry of the airway and the gut and as such are ideally situated to act as immune sentinels in the pharynx protecting against microbial invasion. Tonsils express a number of antimicrobial peptides including hCAP18/LL-37. Here we clearly define the expression of hCAP18/LL-37 in the tonsils showing unequivocally that hCAP18/LL-37 is mainly expressed by infiltrating neutrophils and follicular CD11c+CD13+HLA-DR+ dendritic cells, rarely by macrophages, and never by the epithelium itself. To explore possible functions for follicle-derived LL-37, we stimulated tonsil mononuclear cells with LL-37 in vitro and observed the secretion of the proinflammatory cytokines CCL5 and CXCL9, expression of IFN-γ and MX-1 and down-regulation of chemokine receptors CCR4 and CCR6 which are involved in tissue-selective T cell trafficking. Taken together, these data illustrate new potential immunoregulatory functions for hCAP18/LL-37 in the tonsils.
"It is thought that HBD-1 gene is expressed constitutively and that the production of a peptide is not up-regulated by pathogens (Dunsche et al. 2001, Po-Hsu and Sheen-Yie 2004, Klüver et al. 2006). In the literature some authors have found that the levels of HBD-1 do not differ significantly in various tissue samples (Lee et al. 2002); another text asserts that HBD-1 is reduced in the tonsils of patients with recurrent acute tonsillitis (Ball et al. 2007). Our results show that HBD-1 was detected in larger amounts in healthy nasal mucosa than in the healthy tonsils. "
[Show abstract][Hide abstract] ABSTRACT: The nasal and tonsillar mucosa are exposed to massive incursions of pathological microorganisms. One of the mechanisms known to prevent an invasion of pathogens is an endogenous synthesis of antimicrobial peptides, which include human beta-defensins-1, 2, 3 (HBD-1, 2, 3). The aim of this study was to demonstrate the occurrence of HBD-1, 2 and 3 in the human nasal mucosa and palatine tonsils in healthy tissues and during chronic inflammation (nasal polyposis with and without the colonization of Staphylococcus aureus and chronic tonsillitis) and to evaluate their incidence under varying conditions. Another target was to compare the occurrence of human beta-defensins in these two different entities; that is, in the nasal mucosa and in the palatine tonsil. It was assumed that the incidence of HBD-1, 2, 3 was lower in tonsils than in nasal mucosa; however, inflamed samples of tonsils and nasal mucosa showed no difference in the production of HBD-1, 2, 3. The presence of all three subfamilies of HBD was significantly lower in nasal polyps with S. aureus positive than in the negative control.
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