EXPRESSION OF FAS (CD95) AND FAST (CD95L) IN HUMAN AIRWAY EPITHELIUM

The cell surface molecule Fas (CD95) is a member of the tumor necrosis factor receptor family. Ligation of the Fas receptor can lead to indu ction of apoptosis in inflammatory cells. It has been suggested that e xpression of the Fas receptor and its ligand (FasL) in airway epitheli um may modulate the inflammatory response commonly found in asthmatic lungs. We examined Fas and Fast expression on primary human tissues, o n bronchial epithelial cells in primary culture, and on the immortaliz ed human airway epithelial cell line, 1HAE(o)(-). Receptor and ligand expression were demonstrated using multiple antibodies and multiple te chniques, including immunohistochemistry, flow cytometry, Western blot s, and reverse transcription-polymerase chain reaction (RT-PCR). Immun ohistochemical staining demonstrated that both columnar and basal cell s of intact human lung tissues expressed cell surface Fas and Fast. In addition, both primary cultured and immortalized 1HAE(o)(-) cells exp ressed cell surface Fas and Fast, as demonstrated by flow cytometry; e xpression of Fas and Fast was confirmed at the transcription level usi ng RT-PCR and, for additional confirmation of Fast, using Western blot s. We demonstrate that both Fas and Fast are expressed by human airway epithelial cell subtypes. Expression of these molecules may play an i mportant role in regulation of the inflammatory response.