T follicular helper and T follicular regulatory cells have different TCR specificity

Immunization leads to the formation of germinal centres (GCs) that contain both T follicular helper (Tfh) and T follicular regulatory (Tfr) cells. Whether T-cell receptor (TCR) specificity defines the differential functions of Tfh and Tfr cells is unclear. Here we show that antigenspecific T cells after immunization are preferentially recruited to the GC to become Tfh cells, but not Tfr cells. Tfh cells, but not Tfr cells, also proliferate efficiently on restimulation with the same immunizing antigen in vitro. Ex vivo TCR repertoire analysis shows that immunization induces oligoclonal expansion of Tfh cells. By contrast, the Tfr pool has a TCR repertoire that more closely resembles that of regulatory T (Treg) cells. Our data thus indicate that the GC Tfh and Tfr pools are generated from distinct TCR repertoires, with Tfh cells expressing antigen-responsive TCRs to promote antibody responses, and Tfr cells expressing potentially autoreactive TCRs to suppress autoimmunity.Fundação para Ciência e Tecnologia | Ref. PTDC/SAU-IMU/120225/2010Fundação para Ciência e Tecnologia | Ref. HMSP-ICT/0034/2013Fundação para Ciência e Tecnologia | Ref. FCT-FAPESP/19906/2014Fundação para Ciência e Tecnologia | Ref. SFRH/BD/88030/2012Fundação para Ciência e Tecnologia | Ref. SFRH/BDP/81391/2011European Commission | Ref. PIRSES-GA-2012-317893 (INDOEUROPEAN-MATHDS)European Commission | Ref. REGPOT-2012-2013.1-316265 (BIOCAPS