B1a cells in Periodontitis

Epidemiological evidence suggests periodontitis (PD) is more common in rheumatoid arthritis (RA) patients. B Cells play key roles in both diseases, via antibody and autoantibody production, cytokine secretion and induction of osteoclastogenesis by expression of receptor activator of nuclear factor kappa-B ligand (RANKL). B cell subsets were investigated in human tissue obtained from patients with PD undergoing surgery and in a murine model of PD. B cells were commonly found in human PD patients gingival (n=11), of which less than 1% were B1a (CD19+ CD5+) cells. In the murine model, six weeks post oral infection with P. gingivalis, alveolar bone losswas evident around teeth. In the gingiva of mice with PD, there was a trend towards increased numbers of B1a (CD19+CD43+CD5+), B1b (CD19+CD43+CD5-) and marginal zone (MZ) cells (CD19+CD43-CD23-) and a decrease in B2 follicular (FO) cells (CD19+CD43-CD23+) compared with controls. In the dLN of infected mice, lymphocyte RANKL expression was observed in the gingiva, where it is also highest in B1a cells. Although the percentage of B1a cells is low in both human PD patient gingiva and in the gingiva of mice with PD, the high level of RANKL expression by this B cell subset evident in mice may be of pathological relevance, and this will be further investigated.