Expression and function of Fas antigen in human oral epithelium.

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The Fas antigen is a cell-surface glycoprotein that mediates apoptosis from the cell surface into the cytoplasm. A monospecific and high titer polyclonal antibody, designated as Fas D,was raised against synthetic polypeptides selected from a part of the human Fas antigen (amino acid resideues 104-114). This antibody was used to identify the Fas antigen in human oral epithelia in normal and pathological states. Biopsy specimens of normal human gingiva were prepared and the paraffin sections were reacted with the Fas D antibody by an immunohistochemical method. Specimens obtained from patients with odontogenic Keratocysts, leukoplakia, lichen planus, and squamous cell carcinoma were also stained with the antibody. The pattern of the Fas antigen distribution in oral stratified squamous epithelia was, with some overlapping, characteristic for each disease. The antibody localized to the prickle-cell layr and to granular layr of keratinocytes of human gingiva. Proteins were also prepared from human gingiva and subjected to SDS-PAGE,followed by Western blotting analysis with the Fas D antibody. The antibody interacted with a band cprresponding to an estimated molecular weight of 35 kDa. The incidence of the immunoreactive 35-kDa protein was detected in the gingiva of 90% of the 20 individuals examined. The localization of F as antigen in human oral squamous cell carcinoma also was examined. Out of 24 cases of the well-defferentiated tumors examined, 22 showed Fas-positive staining. Among the moderately differentiated tumors, four out of 11 cases showed Fas-positive staining. No Fas-positive cells were observed in the poorly differentiated tumors, but only three specimens were examined. The Fas antigen detected in human oral epithelia may be related to the physiological turnover of oral mucasa and pathological states in oral mucosa. The expression of Fas antigen also appears to be related to the degree of tumor differentiation.