Within the oral periodontal system, specific subtypes of B cells have been shown to correlate with disease severity, and the B cell-stimulating cytokines BLyS (B lymphocyte stimulator) and APRIL (a proliferation-inducing ligand) have been demonstrated to elevate in periodontitis.[47,48] Therefore, these cells and cytokines may regulate osteoclastogenesis, playing a key role in the progression of periodontitis. The gene discussed is TNFSF13B; the disease is periodontitis.