Immunohistochemical analysis of effects of cyclosporin A on gingival epithelium.

Cyclosporin A (CSA)-induced gingival overgrowth was immunohistochemically compared with that phenytoin-induced and nonspecific inflammatory gingiva, and CSA concentration was determined for dental plaque. Leu-6+ epithelial dendric cells (EDC) were found to significantly decrease in number in CSA-induced gingival overgrowth, while the ratio of HLA-DR+ EDC to Leu-6+ EDC did not change significantly. The expression of class II major histocompatibility complex antigens, such as HLA-DR, -DP and -DQ on keratinocytes did not change by CSA-treatment. Leu-4+ mononuclear cells in CSA-induced gingival overgrowth were located primarily in the connective tissue far outside the epithelium. CSA concentration was much higher in dental plaque than in blood and other tissues. Immune response thus appears to be suppressed in the epithelial layer of CSA-induced gingival overgrowth through decrease in Leu-6+ HLA-DR+ EDC and T cell infiltration, both due to CSA in dental plaque. DNA polymerase alpha was detected in much fewer basal keratinocytes of CSA- and phenytoin-induced gingival overgrowth. Epithelial hyperplasia may thus be not due to increased keratinocyte proliferation, but rather to enhanced keratinocyte life span.