Research ArticleAUTOIMMUNITY

Human blood Tfr cells are indicators of ongoing humoral activity not fully licensed with suppressive function

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Science Immunology  11 Aug 2017:
Vol. 2, Issue 14, eaan1487
DOI: 10.1126/sciimmunol.aan1487

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Suppressing Sjögren syndrome

T follicular regulatory (Tfr) cells regulate antibody production in the germinal center, yet individuals with the autoimmune disease Sjögren syndrome have increased numbers of circulating Tfr cells compared with healthy individuals. Fonseca et al. compared blood Tfr cells with tissue Tfr cells and found that blood Tfr cells were phenotypically distinct from their tissue counterparts. Moreover, blood Tfr cells did not preferentially suppress humoral responses and had a naïve-like phenotype. These cells were not thymically derived but were generated during germinal center responses, exiting the tissue to enter the blood. These data explain why increased number of blood Tfr cells does not correlate with increased suppression potential and suggest that, instead, increased numbers of blood Tfr cells indicate ongoing humoral activity.

Abstract

Germinal center (GC) responses are controlled by T follicular helper (Tfh) and T follicular regulatory (Tfr) cells and are crucial for the generation of high-affinity antibodies. Although the biology of human circulating and tissue Tfh cells has been established, the relationship between blood and tissue Tfr cells defined as CXCR5+Foxp3+ T cells remains elusive. We found that blood Tfr cells are increased in Sjögren syndrome, an autoimmune disease with ongoing GC reactions, especially in patients with high autoantibody titers, as well as in healthy individuals upon influenza vaccination. Although blood Tfr cells correlated with humoral responses, they lack full B cell–suppressive capacity, despite being able to suppress T cell proliferation. Blood Tfr cells have a naïve-like phenotype, although they are absent from human thymus or cord blood. We found that these cells were generated in peripheral lymphoid tissues before T-B interaction, as they are maintained in B cell–deficient patients. Therefore, blood CXCR5+Foxp3+ T cells in human pathology indicate ongoing humoral activity but are not fully competent circulating Tfr cells.

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