Interestingly, higher levels of all the M1 markers STAT1 (r = .75; p < 0.0001), miR‐155 (r = .8; p < 0.0001), TNF‐α (r = .75; p < 0.0001), and CXCL10 (r = .62; p < 0.001) correlated with PPD in the periodontitis group (Figure 2; lower panel). This evidence concerns the gene TNF and periodontitis.