Characteristics of salivary IgA responses to oral microbiota in patients with oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory disease of the oral mucosa with a risk of malignant transformation. Oral bacteria are associated with OLP development and progression; however, the immune response, especially the salivary immunoglobulin A (IgA) response to these bacteria remains poorly understood. Therefore, this study aimed to characterize the salivary microbiota in patients with OLP and evaluate the corresponding salivary IgA response. Stimulated saliva samples were collected from 21 patients with OLP and 56 control participants, and 16S rRNA metagenomic analysis was performed to characterize the composition of the microbiota. In addition, IgA-enriched and non-enriched fractions from the saliva samples were separated via magnetic-activated cell sorting, followed by 16S rRNA metagenomic analysis. To evaluate differences in IgA responses to each bacterium between the two groups, we calculated the IgA index. The diversity and bacterial composition of the salivary microbiota differed considerably between the OLP and control groups. Several bacterial genera, including Leptotrichia, Fusobacterium, and Streptococcus, showed markedly lower IgA index in the OLP group than the control group. In conclusion, patients with OLP exhibited a distinctive salivary IgA response to salivary microbiota, suggesting a potential association between OLP and this altered response.