C3 and periodontitis: Noteworthily, some of the phagosome formation-associated genes that were upregulated in T2DM-related periodontitis (e.g., C3a, C5ar1, and LYN) were also found to be upregulated in other DM complications [24, 25], functioning against microbial invasion and as proinflammatory factors and regulators of immunometabolism [25].