TLR9 and periodontitis: Together with the ligation between bacterial DNA component CpG oligodeoxynucleotides (CpG-ODN) and its receptor TLR9 during P. gingivalis infection, it is valuable to determine the effects of multiple TLR activation (TLR2, TLR4 and TLR9) in the regulation of immune B cell functions in order to understand the role of TLR signaling in infection-associated periodontal pathogenesis.