beta-defensin expression in human mammary gland epithelia

Milk of mammalian species contains a wide spectrum of anti-infectious facto rs, some of which are heat stable. Focusing on recently discovered heat-sta ble antibacterial peptides called defensins, which are expressed in epithel ial tissues such as airway, skin, and kidney, we hypothesized that mammary gland epithelia produce and secrete defensins onto the epithelial surface a nd into milk. Using a reverse-transcription PCR assay, we identified the hu man beta-defensin-1 (hBD-1) gene transcript in a human mammary gland epithe lial cell line, MCF-12A, and in mammary glandular tissue of nine nonlactati ng women. Epithelial cells harvested from milk of lactating women also expr essed hBD-1 mRNA. Presence of hBD-1 peptide in mammary epithelia was confir med by immunostaining with an hBD-1 antibody. In contrast, expression of hu man beta-defensin-2 was not apparent both at mRNA and protein levels. Our f indings Suggest a biologic role of hBD-1 in the human mammary gland.