ヒト腸内に存在するTh17細胞誘導細菌の単離・同定を行った。潰瘍性大腸炎患者の腸内細菌を無菌マウスの腸内へ定着させたところ, 腸管Th17細胞の有意な増加が確認できた。そこでどのような細菌種がTh17細胞の誘導に関与しているのかを特定するため, 抗生剤処理を行った後, Th17細胞の誘導が維持されていたマウスから腸内細菌の培養を行い, クロストリジウム属, ビフィドバクテリウム属, バクテロイデス属など合計20菌株を単離した。これら20菌株のみを腸管へ定着させただけで強いTh17細胞の誘導が見られたことから, ヒト腸内においてこれら20菌株が腸管Th17細胞の誘導に関与していると考えられる。
Th17 cells play a role in host defense against extracellular pathogens and also pathogenesis of multiple inflammatory and autoimmune disorders. I have identified the human gut bacteria that could induce intestinal Th17 cells. Th17 cells were significantly increased in the colon of the germ-free mice inoculated with fecal samples from Ulcerative colitis (UC) patients. This Th17 cell induction was further enhanced when the mice were treated with Ampicillin (Amp) in the drinking water. To isolate Th17-inducing bacterial species, I cultured cecal contents from these UC feces colonized and Amp treated mice. I isolated 20 bacterial strains belonging to Clostridium, Bifidobacterium, Ruminococcus, and Bacteroides and inoculated germ-free mice with these 20 strains. The colonization of these 20 strains strongly induced a robust accumulation of Th17 cells in the colon. Furthermore, nine out of the 20 strains were significantly increased in the microbiomes of UC and Crohn's disease subjects.
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