In an early study investigating treatment of gum tissues with Lactobacillus reuteri (L. reuteri), Tweetman et al. [15] found markedly lower levels of TNF-α and interleukin-8 (IL-8) in the gingival crevicular fluid of patients with periodontal disease versus corresponding levels in healthy controls. The gene discussed is CXCL8; the disease is periodontal disorder.