TY - JOUR T1 - Follicular B Helper T Cells Express Cxc Chemokine Receptor 5, Localize to B Cell Follicles, and Support Immunoglobulin Production JF - The Journal of Experimental Medicine JO - J Exp Med SP - 1545 LP - 1552 DO - 10.1084/jem.192.11.1545 VL - 192 IS - 11 AU - Breitfeld, Dagmar AU - Ohl, Lars AU - Kremmer, Elisabeth AU - Ellwart, Joachim AU - Sallusto, Federica AU - Lipp, Martin AU - Förster, Reinhold Y1 - 2000/12/04 UR - http://jem.rupress.org/content/192/11/1545.abstract N2 - Chemokines and their receptors have been identified as major regulators controlling the functional organization of secondary lymphoid organs. Here we show that expression of CXC chemokine receptor 5 (CXCR5), a chemokine receptor required for B cell homing to B cell follicles, defines a novel subpopulation of B helper T cells localizing to follicles. In peripheral blood these cells coexpress CD45RO and the T cell homing CC chemokine receptor 7 (CCR7). In secondary lymphoid organs, CD4+CXCR5+ cells lose expression of CCR7, which allows them to localize to B cell follicles and germinal centers where they express high levels of CD40 ligand (CD40L), a costimulatory molecule required for B cell activation and inducible costimulator (ICOS), a recently identified costimulatory molecule of the CD28 family. Thus, when compared with CD4+CD45RO+CXCR5− cells, CD4+CD45RO+CXCR5+ tonsillar T cells efficiently support the production of immunoglobulin (Ig)A and IgG. In contrast, analysis of the memory response revealed that long-lasting memory cells are found within the CD4+CD45RO+CXCR5− population, suggesting that CXCR5+CD4 cells represent recently activated effector cells. Based on the characteristic localization within secondary lymphoid organs, we suggest to term these cells “follicular B helper T cells” (TFH). ER -