Anti-M3 Muscarinic Acetylcholine Receptor Autoantibody in the Serum and Saliva of Oral Lichen Planus Patients: A Case-Control Study.

Background and Aims: Oral lichen planus OLP) is a chronic, T-cell-mediated disease frequently accompanied by xerostomia. Prior work suggests reduced salivary M3 muscarinic acetylcholine receptor (M3R) may contribute to hyposalivation. We investigated whether anti-M3R autoantibodies are elevated in serum and saliva of OLP patients compared with healthy controls. Methods: In this case-control study, we enrolled 30 patients with OLP and 30 matched healthy controls. Exclusion criteria eliminated confounders of salivary dysfunction. Unstimulated and stimulated salivary flow rates were collected under standardized conditions; venous blood was drawn. Anti-M3R autoantibody levels were measured in serum and in both saliva fractions using enzyme‑linked immunosorbent assay. Group comparisons used independent Results: Stimulated salivary flow was lower in OLP versus controls (0.67 ± 0.12 vs. 1.20 ± 0.22 mL/min; Conclusion: OLP patients showed significantly reduced stimulated and unstimulated salivary flow and higher xerostomia scores, but no elevation of anti-M3R autoantibodies in serum or saliva versus controls. These findings suggest that mechanisms other than circulating anti-M3R autoantibodies-such as receptor functional alterations, salivary composition changes, or other immune pathways-may underlie xerostomia in OLP. Future studies should consider more sensitive detection methods, concurrent immunoglobulin isotype assessment, and tissue-level analyses to clarify M3R-related dysfunction.