Prevotella nigrescens in mice can induce periodontal disease and promote immune responses such as increasing T helper type 17 (Th17) (i.e., interleukin (IL-17)) and Th1 (interferon-γ (IFN-γ)) cytokine production by lymph node T cells compared with uninfected mice [35]. Here, IL17A is linked to periodontal disorder.