Although, H2S can trigger the secretion of pro-inflammatory cytokines from both PBMCs of periodontitis patients and healthy controls, the differences between these two groups of patients, that is, the secretion of MCP-1 and IL-8, may be indicative of differences in host response between the periodontitis susceptible and periodontitis unaffected subjects. This evidence concerns the gene CXCL8 and periodontitis.