CD274 and periodontitis: The authors hypothesized that the upregulation of PD-L1 in advanced periodontitis may represent a local mechanism to inhibit the destruction of inflammatory tissues [35]. The PICO analysis is presented in Table 3, and the summary of exosomal roles across major biological processes (pyroptosis, macrophage polarization, angiogenesis, and immune modulation) in periodontitis is presented in Table 4.