title: The elusive identity of T follicular helper cells.
abstract: Follicular helper T (Tfh) cells provide help to B cells and allow formation of long-lived antibody responses. Despite an improved understanding of the molecular program that drives Tfh cell formation, their definition remains elusive: neither follicular homing ability, Bcl-6 expression nor IL-21 secretion are exclusive properties of T cells that help B cells, and not all follicular T cells are B cell helpers. Indeed some follicular T cells appear to be suppressive. Furthermore, Tfh cells evolve during an immune response and B cells that have recently bound antigen, germinal center (GC) B cells and plasmablasts interact with phenotypically distinct Tfh cells. Here we propose that distinction between non-GC Tfh and GC Tfh cells might reconcile emerging controversies on Tfh cytokine secretion and the requirement of T-B cell interactions and SAP expression for Tfh formation.
authors.affiliation: Immunology, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia.
authors.forename: Di
authors.initials: D
authors.lastname: Yu
authors.forename: Carola G
authors.initials: CG
authors.lastname: Vinuesa
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology; D002454:Cell Differentiation; D018858:Germinal Center / Q000276:immunology; D006801:Humans; D010641:Phenotype; D006377:T-Lymphocytes, Helper-Inducer / Q000166:cytology / Q000276:immunology*