Is the T follicular regulatory: Follicular helper T cell ratio in blood a biomarker for ectopic lymphoid structure formation in Sjogren's syndrome? Comment on the article by Fonseca et al

We read with great interest the article by Fonseca et al (1), that was published in a recent issue of Arthritis & Rheumatology. The authors elegantly showed that T follicular regulatory (Tfr) cells were enriched in blood as well as in matched minor salivary gland (MSG) biopsies from patients with primary Sjögren's syndrome (pSS). They also showed that the Tfr/Tfh ratio in blood was increased in pSS compared to non-SS sicca patients. Interestingly, this Tfr/Tfh ratio in blood correlated with ectopic lymphoid structure formation in MSG tissue. To our opinion the authors did, however, not show a direct correlation between aberrant Tfr/Tfh ratios and ectopic lymphoid structure formation among pSS patients. In essence their study showed that in pSS patients the Tfr/Tfh ratio in blood was correlated with numbers of infiltrating lymphocytes, as assessed by flow cytometric analysis of MSG cell suspensions. Additionally, the authors showed that the Tfr/Tfh ratio in blood was increased in patients with focal sialoadenitis (FSA) (defined in their study as a focus score ≥1), compared to patients without FSA. Of note, this comparison was made irrespective of a diagnosis of pSS, which implicated that the majority of patients without FSA were non-SS sicca patients. This article is protected by copyright. All rights reserved.