In the early stage of COPD (2 weeks of smoke exposure), RT-qPCR results showed that the expression levels of Il 17 and Ifn γ, M1 polarization, and M2 polarization-related markers and inflammatory cytokines (CD86, iNOS, Il 1β, Il 23, Mmp 9, Mmp 12, Il 4) in COPD lung tissues were significantly up-regulated under the condition of periodontitis (Fig. 3A; Fig. S1a). Here, CD86 is linked to periodontitis.