Cytokines mediate the balance between protective and destructive immunity in periodontitis. We sought to investigate the role of IL-33 in periodontitis. The expression of IL-33 in gingival tissue from healthy controls (n = 10) and patients with chronic periodontitis (n = 17) was investigated. Based on a murine model of periodontal disease, the function of IL-33 was determined first by administration of exogenous IL-33 and second by inhibition of IL-33 signaling using mice deficient in the IL-33 receptor ST2. Alveolar bone level, serum antibody, and lymphocyte responses were assessed in the murine model. Expression of IL-33 and ST2 was elevated in gingival tissues from patients with chronic periodontitis as compared with healthy tissues (P < 0.05). Similarly, Il33 expression was higher in periodontal tissues of Porphyromonas gingivalis-infected mice as compared with sham-infected controls (P < 0.05). IL-33 treatment of P. gingivalis-infected mice significantly exacerbated alveolar bone loss when compared with infection or IL-33 treatment alone (P < 0.001). Conversely, P. gingivalis infection-induced alveolar bone loss was attenuated in mice lacking ST2. The percentages of T and B lymphocytes expressing nuclear factor κB ligand (RANKL) in the gingival tissues and T lymphocytes expressing RANKL in the cervical draining lymph nodes were higher in IL-33-treated P. gingivalis-infected mice versus phosphate buffered saline-treated P. gingivalis-infected controls (all P < 0.001). Targeting the RANKL pathway by osteoprotegerin administration abrogated periodontal bone destruction in P. gingivalis-infected, IL-33-treated mice. These data demonstrate a previously unrecognized role for IL-33 in exacerbating bone loss in a RANKL-dependent manner in the context of bacterial infection and suggest that this pathway may be amenable to manipulation as a novel therapeutic target in periodontitis.

The microbial plaque biofilm resides adjacent to the tissue-destructive inflammatory infiltrate in periodontitis. Although not sufficient, this biofilm is necessary for this inflammatory response. Patients with periodontitis generate antibodies specific for bacteria in the biofilm - although the role of these antibodies is not clear, there is, undoubtedly, an adaptive immune response in periodontitis. T lymphocytes are central to adaptive immunity, and provide help for B cells to generate specific antibodies. T-cell receptor recognition of peptide antigen in the context of major histocompatibility complex can result in T-cell activation. The activation and differentiation of the T-cell can take many forms, and hence numerous types of T cells have been described. The role of adaptive immune responses, and the T-cell component thereof, in periodontitis remains relatively poorly defined. This review aims to broadly summarize findings about T cells and their role in periodontitis, focusing primarily on studies of human disease with a short discussion of some animal studies.

Periodontitis (PD) results from complex interactions between a dysbiotic oral microbiota and a dysregulated host immune response. The inflammatory infiltrate in the gingiva of PD patients includes an abundance of B cells, implicating these cells in the immunopathology. We sought to investigate the role of B cells in PD using a murine model. Wild-type or B-cell-deficient (μMT) mice were orally infected with Porphyromonas gingivalis. One or six weeks following infection, lymphocyte populations in the gingiva and cervical draining lymph nodes (dLN) were analysed by flow cytometry; serum anti-P. gingivalis IgG antibody titers were measured by enzyme-linked immunosorbent assay, and alveolar bone loss was determined. In wild-type mice, the percentage of gingival B cells expressing receptor activator of nuclear factor-κB ligand (RANKL) was significantly increased 1 week post-infection (5.36% control versus 11% PD, P < 0.01). The percentage of Fas(+) GL7(+) germinal centre B cells in the dLN was significantly increased at both 1 week (2.03% control versus 6.90% PD, P < 0.01) and 6 weeks (4.45% control versus 8.77% PD, P < 0.05) post-infection. B-cell-deficient mice were protected from P. gingivalis-induced alveolar bone loss, with a lack of B-cell proliferation and lack of CD4(+) CD44(+) CD62L(-) T-cell generation in the dLN, and absence of serum anti-P. gingivalis antibodies. Our data imply a pathological role for B cells in PD, and that selective targeting of this immune axis may have a role in treating severe periodontal disease.

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Innate lymphoid cells (ILCs) are a population of lymphocytes that act as the first line of immunologic defense at mucosal surfaces. The ILC family in the skin, lungs, and gastrointestinal tissues has been investigated, and there are reports of individual subsets of ILCs in the oral tissues. We sought to investigate the whole ILC population (group 1, 2, and 3 subsets) in the murine gingivae and the lymph nodes draining the oral cavity. We show that ILCs made up a greater proportion of the whole CD45+ lymphocyte population in the murine gingivae (0.356% ± 0.039%) as compared with the proportion of ILCs in the draining lymph nodes (0.158% ± 0.005%). Cytokine profiling of the ILC populations demonstrated different proportions of ILC subsets in the murine gingivae versus the regional lymph nodes. The majority of ILCs in the draining lymph nodes expressed IL-5, whereas there were equal proportions of IFN-γ- and IL-5 expressing ILCs in the oral mucosa. The percentage of IL-17+ ILCs was comparable between the murine gingivae and the oral draining lymph nodes. These data suggest an enrichment of ILCs in the murine gingivae, and these ILCs reflect a cytokine profile discrepant to that of the local draining lymph nodes. These studies indicate diversity and enrichment of ILCs at the oral mucosal surface. The function of ILCs in the oral cavity remains to be determined; here, we provide a premise of ILC populations that merits future consideration in investigations of mouse models and human tissues.

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The Antonine Wall was commissioned by the Roman Emperor Antoninus Pius around 142 CE and stretches for c. 60 km across the central belt of Scotland, marking the Empire’s most north-western frontier. This vanguard research reports on the materials referred to by Antiquarian sources as having been applied during the sixteenth century for the redecoration of an iconic Distance Sculpture that was once embedded into the mural barrier. Portable non-invasive technologies, including pXRF and in-situ microphotography were deployed. These techniques were further supplemented by micro-sampling for SEM/EDS, FTIR–ATR and microscopy of embedded cross-sections. The validity of applying these complementary techniques has been confirmed. They provide a comprehensive account of the polychromy present, including pigments that could have been applied during the Roman period and others that were only available from the fifteenth or sixteenth Centuries. The work has confirmed stratigraphic sequencing of the pigments which will, in due course, permit the digital reconstruction of how this Classical relief sculpture would have been adorned during the Renaissance.