Mast cell degranulation and the role of T cell RANTES in oral lichen planus

OBJECTIVES: The present study investigated mast cell degranulation in oral lichen planus (OLP) and the effect of OLP lesional T cell supernatants on mast cell degranulation. MATERIALS AND METHODS: Immunohistochemistry was used to identify mast cell degranulation in both OLP (n = 22) and normal control (n = 14) tissues. OLP lesional T cell lines (n = 5) and HMC-I (a human leukemia mast cell line) were used to examine the effects of OLP T cell supernatants on mast cell degranulation in vitro. RESULTS: Approximately 60% of mast cells were degranulated in OLP. OLP lesional T cells expressed mRNA for RANTES, and TNF-alpha stimulation upregulated OLP lesional T cell RANTES secretion. OLP lesional T cell supernatants induced degranulation of HMC-I with release of TNF-alpha and histamine. Human recombinant RANTES similarly induced mast cell degranulation. Anti-RANTES antibody blocked OLP lesional T cell supernatant-induced mast cell degranulation. CONCLUSIONS: This study is the first to show that OLP lesional T cells produce and secrete RANTES which triggers human mast cell degranulation. Degranulating mast cells release TNF-alpha which upregulates OLP lesional T cell RANTES secretion. Such a cyclical mechanism may underlie disease chronicity and future therapies may include blocking RANTES or TNF-alpha activity in OLP.