Contribution of FoxP3(+) Tfr cells to overall human blood CXCR5(+) T cells.

The identification that T follicular helper (Tfh) cells is critical for the emergence of germinal centre responses prompted the study of CXCR5-expressing CD4(+) T cell subsets in autoimmunity. However, circulating CXCR5-expressing T cells are heterogeneous by containing Forkhead box protein 3 (FoxP3)(+) T follicular regulatory (Tfr) cells in addition to bona fide Tfh cells. Such heterogeneity may hamper the analysis of the contribution of specific follicular T cell subsets for autoimmune pathogenesis. Therefore, separate assessment of Tfh and Tfr populations offer greater opportunities for stratification of autoimmune patients, such as Sjogren's syndrome patients.