Abstract
The oral mucosa contains distinct tissue sites with immune niches capable of either immunogenic or tolerogenic responses. However, immune cell compositions within oral mucosal tissues at homeostasis have not been well-characterized in human relevant tissues. Non-human primates (NHP) are a major model for the human immune system and oral anatomy, and therefore improved understanding of NHP oral immune cell populations can provide important insights for studying disease pathologies and developing therapies. Herein, we characterize immune cell types of three sites within the oral cavity (buccal, sublingual, lingual tonsil) sampled by biopsy and cytobrush in pigtail macaques. Tonsil biopsies had more T-cells, dendritic cells (DCs), DC subtypes, and CD4+ T-cells than buccal or sublingual biopsies when normalized by tissue mass. Biopsy proved to collect more immune cells than cytobrushes, however frequencies of CD45+ subpopulations were comparable between methods. Live cells isolated from biopsied tonsils had greater CD45+ leukocyte frequencies (mean 31.6 ± SD 20.4%) than buccal (13.8 ± 4.6%) or sublingual (10.0 ± 5.1%) tissues. T-cells composed more than half of the CD45+ population in sublingual tissue (60.1 ± 9.6%) and the tonsil (54.6 ± 7.5%), but only 31.9 ± 7.2% in buccal samples. CD20+ B-cells composed a greater percentage of CD45+ leukocytes in the tonsil (12.8 ± 9.1%) than buccal (1.2 ± 1.0%) or sublingual tissues (0.8 ± 1.2%). Immune population comparisons are also made between sex and age. These results present an important step for understanding the oral immune environment, oral disease, and site-specific therapy development.
Highlights
The oral mucosa is constantly exposed to a plethora of pathogens and a diverse commensal microbiome, all of which require immune control [1]
Serial gating for specific leukocyte populations was performed based on CD45+ cells gated from total live cells extracted from tissue biopsies of each site (Figure 1A)
We identify and quantify immune cell populations across the buccal, sublingual, and lingual tonsil regions of the oral mucosa sampled from the human relevant Non-human primates (NHP) model
Summary
The oral mucosa is constantly exposed to a plethora of pathogens and a diverse commensal microbiome, all of which require immune control [1]. Due to routine exposure to foreign substances like commensal bacterial and food particulates, immune cells of the oral mucosa induce a state of tolerance with regulatory T-cells (Tregs) as the main mediator of immune homeostasis [2, 3]. Oral bacteria generate inflammatory responses from cells like macrophages, mast cells, and neutrophils that can cause chronic oral disease. Such inflammatory responses can degrade oral tissues and are associated with autoimmune disorders and increased risk of various cancers [2]. Local macrophages and B-cells are implicated in oral tumor development [2].
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