Oral Immune Zones Stay Organized Even During Gum Disease

The oral mucosa faces a uniquely demanding immunological challenge: it is thin, minimally keratinized, constantly exposed to a rich and diverse microbiome, and subject to mechanical damage — yet invasive infection and systemic bacteremia remain rare in healthy individuals. Despite this, the spatial organization of immunity at this barrier was largely uncharacterized at cellular resolution. This study provides the first comprehensive multiomics spatial atlas of human gingival tissue in both health and periodontitis.

Using iterative bleaching extends multiplexity (IBEX) spatial proteomics with an 18-marker panel, Xenium spatial transcriptomics with a 450-gene panel, CITE-seq, and spectral flow cytometry, the team profiled over 1 million spatially resolved cells from 28 participants (11 healthy, 17 periodontitis). Biopsies were oriented to simultaneously capture the external oral epithelium (OE) and the tooth-associated epithelium (TAE), enabling direct anatomical comparisons.

The central discovery is a striking immune zonation at the gingival barrier. At the tooth-gum interface, the TAE — thin, nonkeratinized, and highly permeable — is underlaid by a dense layer of MPO+ neutrophils that act as a first-line defense. Deeper in the subepithelial connective tissue, discrete aggregates of antigen-presenting cells (APCs) and lymphocytes form a secondary immunological zone. Notably, even in clinically healthy individuals, a 'tonic' inflammatory infiltrate was consistently observed adjacent to the TAE, suggesting that baseline homeostatic inflammation is a defining structural feature of this tissue rather than a pathological finding.

In periodontitis, these zones do not disintegrate but instead expand and reorganize. Inflammatory infiltrates extend into deeper connective tissue, and APC-lymphocyte aggregates evolve into immature tertiary lymphoid structures (TLS), complete with plasma cell accumulation (CD45+CD138+ cells), pointing to the potential for local antibody production at the disease site. Spatial transcriptomics revealed location-specific gene expression patterns in stromal fibroblasts that align with immune zone boundaries, strongly implicating the stromal compartment as a key organizer of this spatial immune architecture — a concept with parallels to Peyer's patches in the intestine and immunological hubs around hair follicles in skin.

These findings reframe our understanding of oral mucosal immunity. The oral barrier appears to maintain a constitutively primed, spatially ordered immune state that scales with microbial challenge without collapsing into uncontrolled infection or scarring. The emergence of TLS in periodontitis suggests that local adaptive immunity, including antibody responses, is an active component of disease — with potential implications for vaccine strategies and therapeutic targeting in inflammatory oral and systemic diseases linked to periodontitis.