Clonally Convergent Tph/Tfh-like CD4+ T Cells are Shared Across Recovery and Recurrence in Experimental Periodontitis

Periodontitis is a chronic inflammatory disease of the tooth-supporting structures (periodontium) that requires life-long maintenance to prevent progression. Using a sensitized model of recurrent periodontitis in mice (SeRPD), in which regulatory breakdown was induced by temporary Treg depletion concurrent with disease, we mapped the gingival T cell imprint across each disease phase. Transient regulatory breakdown left a durable mucosal imprint after clinical recovery, characterized by enrichment of local and regional CD4 T cells. Paired single-cell RNA and TCR sequencing of gingival immune cells identified a convergent clonotype expanded from recovery into recurrence that carried a Tfh/Tph-like transcriptional identity. An analogous CD4 T cell population was detected in human periodontitis lesions by single-cell transcriptomics. Together, these findings support a paradigm in which clinical recovery does not ensure a local T cell repertoire reset; instead, a reservoir of antigen-experienced, tissue-adapted CD4 T cells persist in the mucosa and participate in recurrence.