title: Insights into the role of follicular helper T cells in autoimmunity.
abstract: Follicular helper T (TFH) cells are recently highlighted as their crucial role for humoral immunity to infection as well as their abnormal control to induce autoimmune disease. During an infection, naïve T cells are differentiating into TFH cells which mediate memory B cells and long-lived plasma cells in germinal center (GC). TFH cells are characterized by their expression of master regulator, Bcl-6, and chemokine receptor, CXCR5, which are essential for the migration of T cells into the B cell follicle. Within the follicle, crosstalk occurs between B cells and TFH cells, leading to class switch recombination and affinity maturation. Various signaling molecules, including cytokines, surface molecules, and transcription factors are involved in TFH cell differentiation. IL-6 and IL-21 cytokine-mediated STAT signaling pathways, including STAT1 and STAT3, are crucial for inducing Bcl-6 expression and TFH cell differentiation. TFH cells express important surface molecules such as ICOS, PD-1, IL-21, BTLA, SAP and CD40L for mediating the interaction between T and B cells. Recently, two types of microRNA (miRNA) were found to be involved in the regulation of TFH cells. The miR-17-92 cluster induces Bcl-6 and TFH cell differentiation, whereas miR-10a negatively regulates Bcl-6 expression in T cells. In addition, follicular regulatory T (TFR) cells are studied as thymus-derived CXCR5(+)PD-1(+)Foxp3(+) Treg cells that play a significant role in limiting the GC response. Regulation of TFH cell differentiation and the GC reaction via miRNA and TFR cells could be important regulatory mechanisms for maintaining immune tolerance and preventing autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Here, we review recent studies on the various factors that affect TFH cell differentiation, and the role of TFH cells in autoimmune diseases.
authors.affiliation: Department of Life Science, Hanyang University, Seoul 133-791, Korea. ; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Korea.
authors.forename: Hong-Jai
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Department of Life Science, Hanyang University, Seoul 133-791, Korea. ; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Korea.
authors.forename: Do-Hyun
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Life Science, Hanyang University, Seoul 133-791, Korea. ; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Korea.
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Lim
authors.affiliation: Department of Life Science, Hanyang University, Seoul 133-791, Korea. ; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Korea.
authors.forename: Won-Ju
authors.initials: WJ
authors.lastname: Kim
authors.affiliation: Department of Anatomy & Cell Biology, College of Medicine, Hanyang University, Seoul 133-791, Korea.
authors.forename: Jeehee
authors.initials: J
authors.lastname: Youn
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.
authors.forename: Youn-Soo
authors.initials: YS
authors.lastname: Choi
authors.affiliation: Department of Life Science, Hanyang University, Seoul 133-791, Korea. ; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Korea.
authors.forename: Je-Min
authors.initials: JM
authors.lastname: Choi
keywords: Autoimmunity; Cytokines; Follicular helper T cells; Follicular regulatory T cells; Germinal Center