Expression of the antimicrobial peptide, human beta-defensin 1, in duct cells of minor salivary glands and detection in saliva

The oral cavity is exposed to a variety of environmental insults. Salivary secretions play a critical role in maintaining oral health via innate host defense mechanisms and secretion of secretory IgA. Human beta-defensins (hB D) are antimicrobial peptides that are a component of the innate immune res ponse; they are expressed in epithelia and are proposed to have a role in m ucosal defense, hBD-1 mRNA is constitutively expressed in numerous mucosal tissues, including human gingiva and submandibular and parotid glands. Our objective was to detect the expression and localization of hBD-1 peptide in human salivary glands and in saliva. Minor salivary gland tissue was obtai ned from biopsies of patients with mucoceles (n = 20). hBD-1 peptide was de tected by immunohistochemistry; expression was localized to the ductal cell s and not the acinar cells of these glands. The peptide was located apicall y, toward the lumen in the duct cells. Further evaluation showed stronger h BD-1 expression in ducts with periductal inflammation, as indicated by the immunostaining of serial sections with anti-CD45 specific for B- and T-lymp hocytes. Statistical analysis showed a strong correlation of hBD-1 staining and inflammation. Results of immunolocalization suggest that hBD-1 functio ns to protect salivary glands from retrograde infection, that expression of the peptide is enhanced in inflamed sites, and that posttranscriptional re gulatory mechanisms may be involved in hBD-1 peptide expression. Western im munoblot analysis also detected hBD-1 peptide in unstimulated, whole, acidi fied saliva from normal volunteers. However, hBD-1 peptide associated with salivary mucin resulted in loss of the detection in a dot-immunoblot assay. Association of hBD-1 with salivary mucin may facilitate peptide distributi on and adherence to oral surfaces and aid its function within the oral cavi ty.