Unraveling salivary microbiota diversity following kidney transplantation: insights from baseline peripheral blood lymphocyte subsets.

Background: Effective biomarkers are urgently needed to monitor immune suppression in kidney transplantation (KT) recipients. Our study identified a close association between the salivary microbiota and immunosuppressant concentrations. It is therefore hypothesized that the salivary microbiota may be linked to immune function.

Materials and methods: We analyzed 108 saliva samples from 37 KT patients using 16S rRNA sequencing. Patients were clustered via K-means based on peripheral blood lymphocyte subset (PBLS) counts.

Results: Cluster1 exhibited significantly higher CD4⁺ T cells (p < 0.0001), CD8⁺ T cells (p < 0.0001), and B cells (p = 0.0071) versus Cluster2, with marginally NK cells (p = 0.2319). Beta diversity indicated significant differences in microbial communities. LEfSe analysis identified 34 differential taxa at the genus level. A random forest model in a fivefold three-times repeated cross-validation, developed with differential taxa, discriminated patient groups well (AUC, 75.61% ± 14.54%), with Pseudopropionibacterium most contributing. Meanwhile, only Pseudopropionibacterium correlated with more than 2 PBLSs. Cluster2 was predicted to exhibit more primary and secondary bile acid synthesis, with differential expression of related enzymes.

Conclusion: The absolute count of PBLSs is correlated with the composition of the salivary microbiota, with the strongest association observed between Pseudopropionibacterium and lymphocytes. Our study provides novel insights into immune monitoring post-KT.