Assessment of Anti-M3R antibody in patients with oral lichen planus complaining of xerostomia: a preliminary study

OBJECTIVE: Oral lichen planus (OLP) is a chronic inflammatory disorder mediated by cellular immunity. Xerostomia is not a typical feature but has been reported by a subset of patients and may reflect underlying salivary gland alterations. The mechanisms contributing to xerostomia in OLP remain unclear. This study evaluated the levels of autoantibodies against the muscarinic M3 receptor (anti-M3R Ab) in the labial minor salivary glands, saliva, and serum of OLP patients with xerostomia and compared them with those of healthy controls. METHODS: In this case-control study, unstimulated whole saliva, serum samples, and labial minor salivary gland biopsies were obtained from 35 patients with OLP and xerostomia and 25 healthy controls. Anti-M3R Ab levels were measured using enzyme-linked immunosorbent assay (ELISA). Statistical analyses included Mann-Whitney U test, Spearman correlation coefficients, and multiple logistic regression. RESULTS: Anti-M3R Ab levels were significantly reduced in minor salivary gland tissue of OLP patients compared with controls. Lower anti-M3R Ab levels in minor salivary glands were statistically associated with higher xerostomia scores and lower unstimulated salivary flow rates. Correlation analyses showed a significant inverse relationship between glandular anti-M3R Ab levels and xerostomia severity. CONCLUSIONS: The reduction of anti-M3R Ab within minor salivary gland tissue may represent a localized immunological alteration contributing to xerostomia in OLP. These findings underscore the importance of localized, rather than systemic, immune mechanisms in the salivary gland dysfunction observed in OLP.