Follicular helper T cells and fibrotic diseases.

Persistent Antigen and Germinal Center B Cells Sustain T Follicular Helper Cell Responses and Phenotype

TFH cells regulate antibody affinity and determine the outcomes of anaphylaxis

Allergen-specific immunotherapy modulates the balance of circulating Tfh and Tfr cells

T follicular helper cells mediate local production of allergen-specific IgE and IgG4

Follicular helper T cells in immune homeostasis

ObjectivesMultiple studies suggest that interleukin (IL)-21 plays a pivotal role in the differentiation of B cells and activation of cytotoxic T cells and is involved in the pathogenesis of IgG4-related disease (IgG4-RD). T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT) is a new marker of T follicular helper (Tfh) cells, yet its significance remains unknown. The objective of this study was to investigate whether TIGIT expression could detect high IL-21-producing peripheral Tfh populations and their association with disease activity in IgG4-RD.MethodsTIGIT expression in peripheral CD4+T cell subsets was comprehensively analyzed by multi-color flow cytometry. Single cell mapping was performed by t-SNE method, and IL-21 production was compared in TIGIT+ and TIGIT-T cells. The effect of OX40 signal on cytokine expression was analyzed by RNA-sequencing. Clinical significance of TIGIT+ and TIGIT- peripheral T cells was analyzed in active patients with IgG4-RD, both at baseline and after 12 weeks of glucocorticoid treatment.ResultsUnbiased single cell mapping revealed two high IL-21-producing peripheral T cell populations; TIGIT+ Tfh and TIGIT-T helper cells. OX40 signal was associated with high IL-21 production in TIGIT+ Tfh and TIGIT-T helper cells. IL-21 production in Tfh cells correlated with the proportion of TIGIT+ cells in Tfh cells, serum IgG4 level, and scores of disease activity. Furthermore, the skewing toward peripheral TIGIT+ Tfh cells, particularly TIGIT+Tfh2 subset correlated with disease activity and was corrected by glucocorticoid treatment in IgG4-RD.ConclusionsOX40 is associated with high IL-21 production in peripheral TIGIT+ Tfh cells, and the increase in peripheral TIGIT+ Tfh cells reflects disease activity in IgG4-RD.

BackgroundT follicular helper (Tfh) cells have been identified as a new category of helper T cells, which express CXCR5 on their surface and induce the production of antigen-specific antibodies. Many investigations have found morbid proliferation and/or activation of Tfh cells in systemic autoimmune and allergic diseases. It is also known that Tfh cells are regulated by regulatory B (Breg) cells in the deteriorating such diseases. Recently, CXCL13, a ligand of CXCR5, has been reported to increase in the peripheral blood and lungs of patients with idiopathic pulmonary fibrosis (IPF). This study aimed to investigate the involvement of Tfh cells and Breg cells in IPF.MethodsPeripheral blood samples were obtained from 18 patients with IPF. We isolated heparinized peripheral blood mononuclear cells and investigated the proportions of Breg cells, Tfh cells, PD-1+ICOS+ Tfh cells (activated form of Tfh cells), and the Tfh-cell subsets by flow cytometry. These cell profiles were compared with those of 21 healthy controls. Furthermore, we investigated the correlations between profiles of lymphocytes and lung physiology.ResultsThe median proportions of Tfh cells per total CD4+ T cells and of PD-1+ICOS+ proportion of Tfh cells per total Tfh cells was significantly more in the IPF patients (20.4 and 5.2%, respectively) compared with healthy controls (15.4 and 2.1%, respectively; p = 0.042 and p = 0.004, respectively). The proportion of Tfh2 cells per total Tfh cells was significantly higher and the proportion of Tfh17 was smaller in the IPF patients than healthy controls. The percentage of Breg cells to total B cells was significantly decreased in the IPF patients (median, 8.5%) compared with that in the controls (median, 19.7%; p < 0.001). The proportion of Breg cells was positively correlated with the annual relative change in diffusing capacity of the lungs for carbon monoxide in the IPF patients (r = 0.583, p = 0.018).ConclusionProliferation and activation of Tfh cells and a decrease in Breg cells were observed in the peripheral blood of patients with IPF. The profile of the Tfh-cell subset also changed. Specific humoral immunity aberration would likely underlie complicated pathophysiology of IPF.

T follicular helper (Tfh) cells are a specific subset of CD4 T cells that localize in the B cell follicle and are essential for the Germinal Center (GC) response. Under polarizing environments, Tfh cells produce effector cytokines, including IFN-γ and IL-4. Beyond promoting class switching, the role played by the different subsets of cytokine-producing Tfh cells remains largely unexplored. Using an influenza infection model, we show here that Tfh cells switch from producing IFN-γ early after infection to mainly producing IL-4 at later time points. Importantly, IFN-γ and IL-4-producing Tfh cells differently control the GC B cell response to influenza. Whereas IL-4-producing Tfh cells help GC maintenance late after infection, interaction with IFN-γ producing Tfh cells skews the GC B cell response towards the memory differentiation pathway early after infection. Consequently, lung-memory B cells fail to differentiate in the absence of IFN-γ producing Tfh cells. Collectively, our results support a model in which temporary changes in cytokine production by Tfh cells dynamically control the outcome of the GC response. Hence, our data provide new insights into GC fate decisions following influenza infection. Supported by grants from NIH (R56 AI162698, R01 AI110480)

T follicular helper (Tfh) cells play an essential role in the development of antigen-specific B cell immunity. Tfh cells regulate the differentiation and survival of activated B cells outside and inside germinal centers (GC) of secondary lymphoid organs. They act through cognate contacts with antigen-presenting B cells, but there is no current marker to specifically identify those Tfh cells which productively interact with B cells. Here we show that neuropilin 1 (Nrp1), a cell surface receptor, is selectively expressed by a subset of Tfh cells in human secondary lymphoid organs. Nrp1 expression on Tfh cells correlates with B cell differentiation in vivo and in vitro, is transient, and can be induced upon co-culture with autologous memory B cells in a cell contact-dependent manner. Comparative analysis of ex vivo Nrp1+ and Nrp1- Tfh cells reveals gene expression modulation during activation. Finally, Nrp1 is expressed by malignant Tfh-like cells in a severe case of angioimmunoblastic T-cell lymphoma (AITL) associated with elevated terminal B cell differentiation. Thus, Nrp1 is a specific marker of Tfh cells cognate activation in humans, which may prove useful as a prognostic factor and a therapeutic target in neoplastic diseases associated with Tfh cells activity.

In Africa, many new family planning clients are not menstruating at the time they present for services. Where pregnancy tests are unavailable, clients are often denied their method of choice and sent home to await menses. For pill clients, one obvious solution is 'advance provision' of oral contraceptives for later use. However, this practice is rare in Africa. To assess the level of provider resistance to advance provision of oral contraceptives. We added questions about advance provision of pills to five provider surveys in three African countries. We also used simulated clients in Ghana to assess provider resistance to the practice. In Kenya, only 16% of providers thought it safe to give women oral contraceptives to be started at a later date. In Ghana and Senegal, fewer than 5% of providers mentioned advance provision as a way to manage non-menstruating pill clients. Training programmes and service delivery guidelines in developing countries should provide for advance provision of pills to appropriate clients

Upon infection or immunization, dendritic cells (DCs) present antigens (Ags) to naïve CD4 +T cells. As a result, a fraction of the responding CD4 +T cells upregulate Bcl6 and differentiate into T follicular helper (Tfh) cells, which migrate into the B cell follicles. Once in the B cell follicles, Tfh cells help promote the development and maintenance of the germinal centers (GC). Importantly, limiting the number of Tfh cells is critical for maintaining the selective pressure in the GC, thereby allowing the Darwinian selection that leads to affinity maturation. However, the mechanisms that regulate Tfh cell numbers and prevent excessive Tfh help remains unknown. Using an influenza virus infection model, we show here that Tfh cell differentiation is limited to the first 72h of the infection. After this time, whereas DCs continue to present viral antigens and efficiently prime naïve T cells, responding CD4 +T cells fail to upregulate Bcl6 and preferentially differentiate into effector Th1 cells. Mechanistically, we demonstrate that the lack of Tfh cell differentiation after day three was due to the presence of the early-primed Tfh cells. Our results indicate that early-primed Tfh cells produce large amounts of IL-2 in the proximity of the B cell follicles, thereby limiting the differentiation of new Tfh cells after day three. Collectively, our data demonstrate that early-primed Tfh cells act as a self-regulating factor that shields the B cell follicles early after infection, thereby preventing the continuous differentiation of Tfh cells regardless of the presence of viral antigens. These data demonstrate a new self-competitive mechanism that critically contributes to limiting Tfh cell expansion after infection. This work was supported by The University of Alabama at Birmingham (UAB) and the National Institutes of Health grant 1R01AI162698-01A1 to A.B.-T

Expansion of T Follicular Helper Cells in NLC Co-Cultures Reinforces the Concept of Co-Evolution of CLL and Supportive T Helper Cell Clones

Human T follicular helper (Tfh) cells are classified into three subsets: Tfh1, Tfh2, and Tfh17 cells. Among them,Tfh2 cells are defined as CXCR3-negative and CCR6-negative, and may contain diverse cell populations. We examined whether CCR4 serves as a marker for identifying Tfh2 cells that produce interleukin (IL)-4 and its involvement in IgG4-related disease (IgG4-RD). Single cell analysis of IL-4-producing Tfh subset was performed using multi-colour flow cytometry and t-SNE method. Blood samples were obtained from 23 treatment-naïve patients with active IgG4-RD. CCR4+Tfh2 cells were also assessed in affected tissues of IgG4-RD by flow cytometry and immunohistochemical staining. Tfh2 cells expressing CCR4 were identified as Tfh cells that specifically produce IL-4. CCR4+Tfh2 cells showed higher expression of GATA-3 and ICOS than CCR4-Tfh2 cells, while there was no difference in the expression of BCL-6 and FOXP3. The proportion of CCR4+Tfh2 cells in peripheral blood was increased in IgG4-RD compared to healthy controls, and even more CCR4+Tfh2 cells infiltrated into the affected lesions. CCR4+GATA-3+Tfh2 cells diffusely infiltrated tertiary lymphoid tissues and storiform fibrosis lesions. The proportion of CCR4+Tfh2 cells showed a significant correlation specifically with serum IgG4 levels among clinical indicators. Glucocorticoid therapy did not correct the increased proportion of CCR4+Tfh2 cells. CCR4 serves as a marker for identifying Tfh2 cells that specifically produce IL-4. CCR4+Tfh2 cells are a widely present T cell population that infiltrates tertiary lymphoid tissues and storiform fibrosis of IgG4-RD. Glucocorticoid fails to effectively target CCR4+Tfh2 cells that may contribute to a high relapse rate during glucocorticoid tapering in this disease.

The elusive identity of T follicular helper cells

T follicular helper (Tfh) cells, a subset of CD4+ T cells, critically regulate the adaptive immune response by promoting germinal center (GC) B cell maturation into memory B cells and antibody secreting plasma cells. Tfh cells promote the GC response through the production of canonical cytokines IL-21 and IFNg, or IL-4 and CD40L signaling. Tfh cells progressively differentiate to regulate the germinal center response, but other than previous studies using cytokine reporter mice, the stages of this differentiation remain unclear. We identified that CD9, a tetraspanin protein, is temporally upregulated on a subset of Tfh cells following acute LCMV infection. To assess the function of the CD9 expressing Tfh cells, we compared migration to GC honing chemokines CXCL12 and CXCL13 and cytokine production between CD9hi and CD9lo Tfh cells at 8 days post LCMV infection. We found that CD9hi Tfh cells exhibited enhanced migration to CXCL12 and CXCL13 compared to CD9lo cells. Ex vivo stimulation of Tfh cells revealed that the CD9hi subsets were the primary producers of IL-21 and IFNg. Transcriptional analysis demonstrated that that CD9hi and CD9lo Tfh cells are distinct subsets characterized by enhanced expression of cell cycling genes in the CD9hi fraction. Thus, not only does CD9 identify the cytokine producing population of Tfh cells but marks a functionally and transcriptionally distinct subset promoting GC responses during viral infections.