Because IL-8 mediates neutrophil migration and activation from peripheral blood to tissue [19, 20] and TNFA is a potent pro-inflammatory cytokine that increases the production of collagenases, prostaglandins, chemokines, cell adhesion molecules and bone resorption-related factors [21, 22], increased expression of these mediators by bacterial-stimulated leukocytes from S-haplotype subjects may correlate with more pronounced inflammation and greater severity of periodontitis. The gene discussed is CXCL8; the disease is periodontitis.