In the past decades, the fields of microbiology and immunology have largely advanced by using germ-free animals and next-generation sequencing. Many studies revealed the relationship among gut microbiota, activation of immune system, and various diseases. Especially, some gut commensals can generate their antigen-specific T cells. It is becoming clear that commensal bacteria have important roles in various autoimmune and inflammatory diseases, such as autism, rheumatoid arthritis (RA), and inflammatory bowel diseases (IBD). Recently, it was reported that commensals contribute to the cancer immune therapy. However, how commensal-specific T cells contribute to the disease development and cancer treatment are not fully understood yet. In this chapter, we will summarize the decade history of the studies associated with commensal-induced T cells and commensal-causing diseases.

在过去的几十年中，微生物学和免疫学领域已通过使用无菌动物和下一代测序技术得到了很大的发展。许多研究揭示了肠道菌群，免疫系统激活和各种疾病之间的关系。特别是，某些肠道菌可以产生其抗原特异性T细胞。众所周知，共生细菌在各种自体免疫和炎性疾病（例如自闭症，类风湿性关节炎（RA）和炎性肠病（IBD））中具有重要作用。最近，据报道，表彰有助于癌症的免疫治疗。然而，尚未完全了解共生特异性T细胞如何促进疾病发展和癌症治疗。在这一章当中，