Clonal Persistence of Tissue-Adapted CD4+ T Cells Drives Recurrent Oral Mucosal Inflammation 2309294

Introduction The oral mucosa is a major immunological barrier and a primary site of interaction between the host immune system and the oral microbiome. Periodontitis is a highly prevalent, recurrent inflammatory disease of the gingiva characterized by tissue destruction; however, the immunological mechanisms driving disease relapse remain poorly understood. We hypothesized that recurrence is driven by clonally expanded, antigen-experienced CD4+ memory T cells that persist in the tissue after microbial challenge resolution and retain effector programs biased toward Th1 and Th17 lineages. Methods We used imaging mass cytometry of human gingival samples and a mouse model of recurrent periodontitis that combined transient regulatory T cell (Treg) depletion to enhance CD4+ T cell recruitment without altering antigen specificity. Disease resolution was confirmed by alveolar bone micro-CT. We next performed integrated single-cell RNA sequencing, paired with T cell receptor (TCR) sequencing, of gingival cells to define transcriptional states and clonal architecture of gingival CD4+ T cells in disease recovery and recurrence. Results In human gingival samples, we identified enrichment of peri-epithelial CD45RO+ CD4+ T cells in periodontitis, consistent with retention of antigen-experienced cells. In recovered mice, there was a significant increase in gingival CD4+ T cell retention (p < 0.05) compared with controls. Clonally expanded CD4+ T cells displayed transcriptional signatures of tissue-resident memory and expression of inhibitory checkpoints associated with chronic activation. Highly expanded clonotypes persisted across recovery and recurrence and maintained stable Th1 effector programs, while acquiring Th17 features. Conclusion These findings implicate tissue-adapted, clonally expanded CD4+ T cells as potential drivers of recurrent oral mucosal inflammation and highlight adaptive immune memory as a therapeutic target for preventing periodontitis and peri-implantitis.