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Common variable immunodeficiency (CVID) is the most frequent primary antibody deficiency whereby follicular helper T (Tfh) cells fail to establish productive responses with B cells in germinal centers. Here, we analyzed the frequency, phenotype, transcriptome and function of circulating Tfh (cTfh) cells in CVID patients displaying autoimmunity as an additional phenotype. A group of patients showed a high frequency of cTfh1 cells and a prominent expression of PD-1 and ICOS, as well as a cTfh mRNA signature consistent with highly activated, but exhausted, senescent and apoptotic cells. Plasmatic CXCL13 levels were elevated in this group and positively correlated with cTfh1 cell frequency and PD-1 levels. Monoallelic variants in RTEL1, a telomere length- and DNA repair-related gene, were identified in four patients belonging to this group. Their blood lymphocytes showed shortened telomeres, while their cTfh were more prone to apoptosis. These data point toward a novel pathogenetic mechanism in CVID, whereby alterations in DNA repair and telomere elongation might predispose to antibody deficiency. A Th1, highly activated but exhausted and apoptotic cTfh phenotype was associated with this form of CVID. This article is protected by copyright. All rights reserved.

BackgroundCommon variable immunodeficiency (CVID) is the most frequent primary antibody deficiency. A significant number of CVID patients are affected by various manifestations of immune dysregulation such as autoimmunity. Follicular T cells cells are thought to support the development of CVID by providing inappropriate signals to B cells during the germinal center (GC) response.ObjectivesWe determined the possible role of follicular helper (Tfh) and follicular regulatory T (Tfr) cells in patients with CVID by phenotypic, molecular, and functional studies.MethodsWe analyzed the frequency, phenotype, transcriptome, and function of circulating Tfh cells in the peripheral blood of 27 CVID patients (11 pediatric and 16 adult) displaying autoimmunity as additional phenotype and compared them to 106 (39 pediatric and 67 adult) age-matched healthy controls. We applied Whole Exome Sequencing (WES) and Sanger sequencing to identify mutations that could account for the development of CVID and associate with Tfh alterations.ResultsA group of CVID patients (n=9) showed super-physiological frequency of Tfh1 cells and a prominent expression of PD-1 and ICOS, as well as a Tfh RNA signature consistent with highly active, but exhausted and apoptotic cells. Plasmatic CXCL13 levels were elevated in these patients and positively correlated with Tfh1 cell frequency, PD-1 levels, and an elevated frequency of CD21loCD38loautoreactive B cells. Monoallelic variants inRTEL1, a telomere length- and DNA repair-related gene, were ideintified in four patients belonging to this group. Lymphocytes with highly shortened telomeres, and a Tfh signature enriched in genes involved in telomere elongation and response to DNA damage were seen. Histopathological analysis of the spleen in one patient showed reduced amount and size of the GC that, unexpectedly, contained an increased number of Tfh cells.ConclusionThese data point toward a novel pathogenetic mechanism in a group of patients with CVID, whereby alterations in DNA repair and telomere elongation might be involved in GC B cells, and acquisition of a Th1, highly activated but exhausted and apoptotic phenotype by Tfh cells.

In the attempt to understand the origin of autoantibody (AAb) production in patients with and at-risk for T1D, multiple studies have analyzed and reported alterations in follicular helper T cells (Tfh) in presymptomatic AAb-positive subjects and patients with T1D. Yet, it is still not clear whether the regulatory counterpart of Tfh cells, represented by follicular regulatory T cells (Tfr), is similarly altered. To address this question, we performed analyses in peripheral blood, spleen and pancreatic lymph nodes (PLN) of organ donor subjects with T1D. Blood analyses were also performed in living AAb-negative and -positive subjects. While negligible differences in the frequency and phenotype of blood Tfr cells were observed between T1D, AAb-negative and AAb-positive adult subjects, the frequency of Tfr cells was significantly reduced in spleen and PLN of T1D as compared to non-diabetic controls. Furthermore, adoptive transfer of Tfr cells delayed disease development in a mouse model of T1D, a finding that could indicate that Tfr cells play an important role in peripheral tolerance and regulation of autoreactive Tfh cells. Together, our findings provide evidence of Tfr cell alterations within disease-relevant tissues in patients with T1D suggesting a role for Tfr cells in defective humoral tolerance and disease pathogenesis.

Patients with Down syndrome (DS) are characterized by increased susceptibility to autoimmunity and respiratory tract infections that are suggestive of humoral immunity impairment. Here, we sought to determine the follicular helper (Tfh) and follicular regulatory (Tfr) T cell profile in the blood of children with DS. Blood was collected from 24 children with DS, nine of which had autoimmune diseases. Children with DS showed skewed Tfh differentiation towards the CXCR3+ phenotype: Tfh1 and Tfh1/17 subsets were increased, while Tfh2 and Tfh17 subsets were reduced. While no differences in the percentage of Tfr cells were seen, the ratio of Tfh1 and CXCR3+PD-1+ subsets to Tfr cells was significantly increased in the affected children. The excessive polarization towards a CXCR3+ phenotype in children with DS suggests that re-calibration of Tfh subset skewing could potentially offer new therapeutic opportunities for these patients. Patients with Down syndrome (DS) are characterized by increased susceptibility to autoimmunity and respiratory tract infections that are suggestive of humoral immunity impairment. Here, we sought to determine the follicular helper (Tfh) and follicular regulatory (Tfr) T cell profile in the blood of children with DS. Blood was collected from 24 children with DS, nine of which had autoimmune diseases. Children with DS showed skewed Tfh differentiation towards the CXCR3+ phenotype: Tfh1 and Tfh1/17 subsets were increased, while Tfh2 and Tfh17 subsets were reduced. While no differences in the percentage of Tfr cells were seen, the ratio of Tfh1 and CXCR3+PD-1+ subsets to Tfr cells was significantly increased in the affected children. The excessive polarization towards a CXCR3+ phenotype in children with DS suggests that re-calibration of Tfh subset skewing could potentially offer new therapeutic opportunities for these patients.

Autoantibodies (AAbs) are a hallmark of Type 1 diabetes (T1D). Alterations in the frequency and phenotype of follicular helper (Tfh) T cells have been previously documented in patients with type 1 diabetes (T1D), but the contribution of follicular regulatory T (Treg) cells, which are responsible for suppressing AAb development, is less clear. Here, we investigated the frequency and activation status of follicular (CXCR5

Background:Clinical improvement after B-cell depletion with rituxmab suggests a prominent pathogenic role of B-lymphcytes in IgG4-related disease (IgG4-RD). IgG4-RD, however, relapses in most cases together with re-expansion of clonally divergent plasmablasts indicating that treatment with rituximab does not completely abrogates T follicular helper (Tfh)-cells dependent germinal center reactions leading to de-novo plasmablast differentiation.Objectives:In the present work we aim to study the effects of B-cell depletion therapy with rituximab on circulating Tfh cells and on the levels of CXCL13 - a chemotactic factor for B-lymphocytes produced by Tfh cells - in patients with IgG4-RD.Methods:Thirty patients with IgG4-RD, diagnosed according to the “Consensus Statement on the Pathology of IgG4-RD” and fulfilling the “2019 ACR/EULAR Classification Criteria” were included in the present study. Ten patients with relapsing disease were treated with the anti-CD20 monoclonal antibody rituximab (two 1g infuxions 15 days apart). Peripheral blood mononuclear cells and serum were collected before rituximab and three months after infusion. Tfh cells subsets in the peripheral blood were measured by flow cytometry and CXCL13 plasma levels were measured by ELISA assay.Results:No changes in total Tfh cells and Tfh cells subsets were observed three months after rituximab neither in absolute counts nor in percentage of CD4+ T cells. In particular, no difference in Tfh1, Tfh2, Tfh17, T follicular regulatory and highly functional Tfh cells counts was observed before and after treatment. The serum level of CXCL13 was significantly higher in active untreated IgG4-RD patients compared to healthy controls (151.94 pg/ml vs 66.98 pg/ml, p value = 0.0026), but was not affected by rituximab treatment (p value = 0.41).Conclusion:In relapsing patients with IgG4-RD rituximab does not affect circulating Tfh cells numbers and serum levels of CXCL13. Persistence of Tfh cells after rituximab and reconstitution of germinal center reactions likely drives IgG4-RD flare.References:[1]Lanzillotta M, Mancuso G, Della-Torre E. Advances in the diagnosis and management of IgG4 related disease. BMJ. 2020 Jun 16;369:m1067. doi: 10.1136/bmj.m1067. PMID: 32546500.[2]Lanzillotta M, Della-Torre E, Stone JH. Roles of Plasmablasts and B Cells in IgG4-Related Disease: Implications for Therapy and Early Treatment Outcomes. Curr Top Microbiol Immunol. 2017;401:85-92. doi: 10.1007/82_2016_58. PMID: 28091934.[3]Campochiaro C, Ramirez GA, Bozzolo EP, Lanzillotta M, Berti A, Baldissera E, Dagna L, Praderio L, Scotti R, Tresoldi M, Roveri L, Mariani A, Balzano G, Castoldi R, Doglioni C, Sabbadini MG, Della-Torre E. IgG4-related disease in Italy: clinical features and outcomes of a large cohort of patients. Scand J Rheumatol. 2016;45(2):135-45. doi: 10.3109/03009742.2015.1055796. Epub 2015 Sep 23. PMID: 26398142.[4]Mattoo H, Mahajan VS, Della-Torre E, Sekigami Y, Carruthers M, Wallace ZS, Deshpande V, Stone JH, Pillai S. De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease. J Allergy Clin Immunol. 2014 Sep;134(3):679-87. doi: 10.1016/j.jaci.2014.03.034. Epub 2014 May 6. PMID: 24815737; PMCID: PMC4149918.Disclosure of Interests:None declared