Of the 20 cytokines examined (details in Supplementary Table 5), CRP was significantly (one-way ANOVA, P < 0.05) higher in the GCF of the periodontitis group while IL-8 was significantly (one-way ANOVA, P < 0.01) higher in the GCF of the healthy group. Here, CXCL8 is linked to periodontitis.