Human tonsil B-cell lymphoma 6 (BCL6)-expressing CD4+ T-cell subset specialized for B-cell help outside germinal centers

Human Extrafollicular CD4+ Th Cells Help Memory B Cells Produce Igs

Follicular helper T (Tfh) cells are necessary for germinal center B cell maturation during primary immune responses; however, the T cells that promote humoral recall responses via memory B cells are less well defined. In this article, we characterize a human tonsillar CD4⁺ T cell subset with this function. These cells are similar to Tfh cells in terms of expression of the chemokine receptor CXCR5 and the inhibitory receptor PD-1, IL-21 secretion, and expression of the transcription factor BCL6; however, unlike Tfh cells that are located within the B cell follicle and germinal center, they reside at the border of the T cell zone and the B cell follicle in proximity to memory B cells, a position dictated by their unique chemokine receptor expression. They promote memory B cells to produce Abs via CD40L, IL-10, and IL-21. Our results reveal a unique extrafollicular CD4⁺ T cell subset in human tonsils, which specialize in promoting T cell-dependent humoral recall responses.

Potential Pathways Associated With Exaggerated T Follicular Helper Response in Human Autoimmune Diseases

Convincing lines of evidence in both mice and humans show that exaggerated T follicular helper (Tfh) responses is pathogenic in autoimmune diseases. However, the cause of exaggerated Tfh response in humans is still much less clear than in mouse models where genetic factors can be manipulated for in vivo testing. Nonetheless, recent advances in our understanding on the mechanisms of human Tfh differentiation and identification of multiple risk loci in genome-wide association studies have revealed several pathways potentially associated with exaggerated Tfh response in human autoimmune diseases. In this review, we will first briefly summarize the differentiation mechanisms of Tfh cells in humans. We describe the features of “Tfh-like” cells recently identified in inflamed tissues of human autoimmune diseases. Then we will discuss how risk loci identified in GWAS are potentially involved in exaggerated Tfh response in human autoimmune diseases.

The expansion in lymphoid organs of IL-4+ BATF+ T follicular helper cells is linked to IgG4 class switching in vivo

Distinct T follicular helper (T_FH) subsets that influence specific class-switching events are assumed to exist, but the accumulation of isotype-specific T_FH subsets in secondary lymphoid organs (SLOs) and tertiary lymphoid organs has not been hitherto demonstrated. IL-4-expressing T_FH cells are surprisingly sparse in human SLOs. In contrast, in IgG4-related disease (IgG4-RD), a disorder characterized by polarized Ig class switching, most T_FH cells in tertiary and SLOs make IL-4. Human IL-4⁺ T_FH cells do not express GATA-3 but express nuclear BATF, and the transcriptomes of IL-4-secreting T_FH cells differ from both PD1^hi T_FH cells that do not secrete IL-4 and IL-4-secreting non-T_FH cells. Unlike IgG4-RD, IL-4⁺ T_FH cells are rarely found in tertiary lymphoid organs in Sjögren's syndrome, a disorder in which IgG4 is not elevated. The proportion of CD4⁺IL-4⁺BATF⁺ T cells and CD4⁺IL-4⁺CXCR5⁺ T cells in IgG4-RD tissues correlates tightly with tissue IgG4 plasma cell numbers and plasma IgG4 levels in patients but not with the total plasma levels of other isotypes. These data describe a disease-related T_FH subpopulation in human tertiary lymphoid organs and SLOs that is linked to IgG4 class switching.

Elevated levels of follicular T helper cells and their association with therapeutic effects in patients with chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is characterized by an abnormal expansion of mature B cells with variable progression. Follicular T helper (Tfh) cells help B cells differentiate into plasma cells or long-lived memory B cells in germinal centres (GCs). However, the role of Tfh cells in CLL is poorly understand, and whether it plays a critical role in disease progression in vivo is lacking. In this study, we investigate the dynamic change of circulating Tfh cells in peripheral blood from patients with CLL during the treatment periods to evaluate their utility to predict disease progression. Our findings revealed the expansion of circulating CD4⁺CXCR5⁺, CD4⁺ICOS⁺, CD4⁺PD-1⁺ and CD4⁺CXCR5⁺ICOS⁺PD-1⁺ (Tfh) cells but lower serum IL-21 levels and CD4⁺ T cell polarization not only to Tfh2 subtypes but also to Tfh17 subtypes in patients with CLL at pretreatment compared to patients with monoclonal B cell lymphocytosis (MBL) and healthy individuals, especially in those with advanced stage, which indicate these Tfh cells could be employed as a novel indicator for disease progression. Moreover, we observed significant correlations of Tfh17 and immunoglobulin heavy chain variable region (IGHV) mutation. Importantly, significantly decreased CD4⁺ICOS⁺, CD4⁺PD-1⁺ and Tfh cells were found after effective treatments, whereas a significantly high CD4⁺ICOS⁺, CD4⁺PD-1⁺ and Tfh cells were still found in those with progressive disease after treatments, suggesting that circulating CD4⁺ICOS⁺, CD4⁺PD-1⁺, Tfh cells could predict therapeutic effects.

Immune correlates of hepatitis B surface antigen spontaneous seroconversion in hepatitis B e antigen negative chronic hepatitis B patients

BACKGROUND

Hepatitis B surface antigen (HBsAg) seroconversion in HBeAg -ve chronic hepatitis B (CHB) infection is rare, possibly due to poor antigen processing and impaired humoral response. We investigated the role of dendritic cells (DCs), T follicular helper (TFH) cells and plasma B cells in seroconversion.

METHODS

HBeAg -ve (n=135) CHB patients with raised ALT at baseline were followed up. Patients undergoing HBsAg seroconversion (Gr. I, n=11) were compared with non-converters with low (Gr. II, n=17, HBV DNA<2000 IU/mL) or high HBV DNA (Gr. III, HBV DNA >2000 IU/mL, n=17). We measured cell phenotypes (TFH, B and DCs), HBV specific T-cell functionality [using pooled overlapping surface and core peptides], IL21 levels and gene expression analysis by qRT-PCR.

RESULTS

Patients in Gr. I compared to Gr. II and III, had higher IL-21 levels (865 vs 276 vs 111 pg/mL, P=<.0001), TFH (CD4⁺ CXCR5⁺ ) cells (12.3 vs 4.67 vs 2.77, P=<.001), inducible T-cell co-stimulator (ICOS) expression on TFH cells (20.0 vs 13.0 vs 13.68, P=.01), HBsAg specific IL-17 (9.40 vs 2.33 vs 2.61, P=<.001) and TNF-α secreting TFH17 cells (82 vs 1.43 vs 2.33, P=<.001), plasma B (CD19⁺ CD38⁺ ) cells (15.0 vs 5.08 vs 5.57, P=<.001), myeloid (17.80 vs 5.39 vs 2.70, P=<.001) and plasmocytoid DCs (2.6 vs 0.43 vs 0.21, P=<.001). Plasma B-cell frequency (R² =.64, P=.01) and IL-21 levels (R² =.52, P=.003) correlated with anti-HBs titres in patients with HBsAg seroconversion.

CONCLUSIONS

Dendritic cell and TFH cell mediated responses regulate humoral responses against HBV and play a major role in HBsAg seroconversion in CHB patients.

The influence of HK2 blood group antigen on human B cell activation for ABOi-KT conditions

Background

It is well known that ABO blood group system incompatible kidney transplantation (ABOi-KT) is an effective strategy for end-stage renal disease. The main barrier for ABOi-KT is how to keep host B cell activation and blood group antibody titer in low levels. Moreover, the mechanism of B cell activation induced by blood group antigen was unclear in ABOi-KT.

Results

In this study, HK2 cells were identified to express blood group B antigen when cocultured with lymphocytes of blood group A. Optical microscope observation demonstrated that HK2 cells in coculture group gradually decreased. Furthermore, flow cytometer assay identified that T cell phenotypes (CD3⁺, CD3⁺CD4⁺ and CD3⁺CD8⁺) had no significant change and B cell phenotypes (CD19⁺ and CD138⁺) were all significantly enhanced (3.07 and 3.02 folds) at day 4. In addition, immunoturbidimetry analysis demonstrated that blood group B antibody was significantly increased to 2.35 fold at day 4, IgG was significantly increased to 3.60 and 2.81 folds at days 4 and 8 respectively, while IgM had no significant change at the measured time points.

Conclusions

Taken together, B cells were activated and secreted blood group B antibody after treatment with HK2 expressing blood group B antigen. The results of this study maybe useful for further determination of the mechanism of B cell activation after ABO incompatible kidney endothelial cells stimulation.

Electronic supplementary material

The online version of this article (10.1186/s12865-017-0233-9) contains supplementary material, which is available to authorized users.

The effect of tonsillotomy on chronic recurrent tonsillitis in children

OBJECTIVES

The objective of this study is to determine whether partial tonsillectomy (tonsillotomy) impacts the occurrence of acute or recurrent tonsillitis in children.

METHODS

One hundred and eighty patients (1-14 years) were retrospectively surveyed by a questionnaire or by data analysis of a regional database. Subjects who suffered from severe systemic diseases or immunodeficiency syndromes were excluded. Episodes of acute tonsillitis before and after surgery, rate of antibiotic treatment, postoperative hemorrhage, and re-operation were obtained.

RESULTS

Fifty-one patients suffered from preoperative tonsillitis. The rate of reinfection was 9.8%. The frequency of tonsillitis was significantly reduced in children after tonsillotomy (p < .001). Further, tonsillotomy led to a significant reduction of antibiotic treatment (p < .001). The rate of definitive tonsillectomy was 1.1% and thus effectiveness was very high. About 1.7% of all children suffered from postoperative bleeding, of which one (0.6%) required surgical revision. None of the bleedings was life threatening.

CONCLUSIONS

Tonsillotomy is beneficial for patients with recurrent tonsillitis and carries less risk of postoperative complications than tonsillectomy.

High frequency of Bob1lo T follicular helper cells in florid reactive follicular hyperplasia

Florid reactive follicular hyperplasia (FRFH), which is characterized by large germinal centers (GCs) within normal lymphoid follicles, is often observed in benign lesions of lymph nodes and other tissues. Because of the histologic similarity of FRFH to tumorous lesions such as follicular lymphoma, careful pathological examination is required to evaluate such lesions; however, little is known about the mechanism underlying the development of FRFH. In this study, we investigated T follicular helper (Tfh) cells in hyperplastic tonsils of patients with obstructive sleep apnea syndrome (OSA), which frequently exhibits typical FRFH. When we analyzed tonsils of OSA and recurrent tonsillitis (RT) as a control, tonsils of OSA were found to harbor Tfh cells with a nearly 3-fold higher ratio in total CD4⁺ T cells than that in tonsils of RT. Further analysis showed that, in comparison to Tfh cells of RT tonsils, Tfh cells of OSA tonsils were relatively tolerant to CD3-mediated activation-induced cell death (AICD) and also expressed lower levels of a Bob1 transcription coactivator and IL-4, which fosters the development of GC-B cells. Given that Bob1 controls the proliferative activity in response to CD3 stimulation and has been suggested to have a role in the production of IL-4 in Tfh cells, the unique structure of FRFH is possibly associated with the function of Bob1^lo Tfh cells.

The ratio of circulating follicular T helper cell to follicular T regulatory cell is correlated with disease activity in systemic lupus erythematosus

Follicular T regulatory (Tfr) cells inhibit follicular T helper (Tfh) cells mediated B cell responses. Tfh cells are involved in the pathogenesis of systemic lupus erythematosus (SLE). However, the role of Tfr cells in SLE remains unclear. The frequency of circulating Tfr and Tfh cells were examined in SLE patients and healthy controls. The frequency of circulating Tfr cell decreased and Tfh/Tfr ratio increased in SLE patients. Serum anti-dsDNA antibody level positively correlated with frequency of Tfh cells and Tfh/Tfr ratios but negatively correlated with the frequency of Tfr cells. Moreover, the frequency of Tfr and Tfh/Tfr ratio but not that of Tfh was correlated with diseases activity. In addition, increase in Tfr cell numbers and decrease in the Tfh/Tfr ratios were observed with successful treatments. Thus, Tfr cells should be considered as a biomarker for SLE and their role in the pathogenesis of SLE warrants further investigation.

High expressions of BCL6 and Lewis y antigen are correlated with high tumor burden and poor prognosis in epithelial ovarian cancer

Aberrant regulation of BCL6 plays crucial oncogenic roles in various malignant tumors; howbeit, the function of BCL6 in tumorigenesis of ovarian cancer remains unclear. The aim of this study is to investigate the role of BCL6 in ovarian cancer. The methods of immunohistochemical staining, quantitative real-time polymerase chain reaction, immunocytochemical staining, and gene expression profile enrichment analysis were performed to identify the possible role of BCL6 in ovarian cancer. We observed that the expression of BCL6 was significantly higher in ovarian cancer tissues and correlated with higher tumor burden including advanced International Federation of Gynecology and Obstetrics stages, poor differentiation, Type II ovarian cancer, the presence of >1 cm residual tumor size, and appearance of recurrence or death (all p < 0.05). The expression patterns of Lewis y were similar to these of BCL6. Multivariate Cox analysis demonstrated that advanced International Federation of Gynecology and Obstetrics stage, lymph node metastasis, residual tumor size >1 cm, as well as high expressions of BCL6 and Lewis y antigen were independent factors of worse progression-free survival and overall survival (all p < 0.05). There was a positive correlation of the expressions of BCL6 and Lewis y antigen. The associated genes with BCL6 in response to Lewis y antigen were identified, including four upregulated genes ( SOCS3, STAT1, PPARG, and GADD45A) and three downregulated genes ( ACAN, E2F3, and ZBTB7B). In conclusion, the high expressions of BCL6 and Lewis y antigen are associated with development, high tumor burden, and worse prognosis of ovarian cancer and targeting BCL6 could be a novel therapeutic strategy for ovarian cancer treatment.

Vaccination establishes clonal relatives of germinal center T cells in the blood of humans

Heit et al. describe that in humans, circulating memory T follicular helper cells (cTfh) have a clonal relationship to germinal center Tfh (GCTfh) cells. Upon vaccination, such memory cTfh respond with clonal expansion, activation, and simultaneous expression of a GCTfh-like phenotype.

Germinal center T follicular helper cells (GCTfh) in lymphatic tissue are critical for B cell differentiation and protective antibody induction, but whether GCTfh establish clonal derivatives as circulating memory T cells is less understood. Here, we used markers expressed on GCTfh, CXCR5, PD1, and ICOS, to identify potential circulating CXCR5⁺CD4⁺ Tfh-like cells (cTfh) in humans, and investigated their functional phenotypes, diversity, and ontogeny in paired donor blood and tonsils, and in blood after vaccination. Based on T cell receptor repertoire analysis, we found that PD-1–expressing cTfh and tonsillar GCTfh cells were clonally related. Furthermore, an activated, antigen-specific PD1⁺ICOS⁺ cTfh subset clonally expanded after booster immunization whose frequencies correlated with vaccine-specific serum IgG; these phenotypically resembled GCTfh, and were clonally related to a resting PD1⁺ICOS⁻ CD4⁺ memory T cell subset. Thus, we postulate that vaccination establishes clonal relatives of GCTfh within the circulating memory CD4⁺CXCR5⁺PD1⁺ T cell pool that expand upon reencounter of their cognate antigen.

Chronic HIV-1 Infection Impairs Superantigen-Induced Activation of Peripheral CD4+CXCR5+PD-1+ Cells, With Relative Preservation of Recall Antigen-Specific Responses

Peripheral CD4+CXCR5+PD-1+ T cells are a putative circulating counterpart to germinal center T follicular helper (TFH) cells. They show both phenotypic and functional similarities to TFH cells, which provide necessary help for the differentiation of B cells to antibody-secreting plasmablasts. In this study, we evaluated the frequency, phenotypes, and responses of peripheral TFH-like (pTFH) cells to superantigen and recall antigen stimulation in 10 healthy and 34 chronically infected treatment-naive HIV-1+ individuals. There was no difference in the frequency of pTFH cells between HIV+ and HIV- individuals. Surface expression of ICOS, but not CD40L, was higher on pTFH cells at baseline in HIV+ individuals. Compared with HIV- individuals, pTFH cells from HIV+ individuals had decreased maximal expression of ICOS and CD40L in response to in vitro superantigen stimulation. This decreased response did not correlate with viral control, CD4 T-cell count, duration of infection, or the degree of neutralizing antibody breadth. Despite a decreased maximal response, pTFH responses to HIV Gag and tetanus toxoid recall antigens were preserved.

High frequencies of circulating Tfh-Th17 cells in myasthenia gravis patients

Recent studies show that the frequencies of circulating follicullar helper T (cTfh) cells are significantly higher in myasthenia gravis (MG) patients compared with healthy controls (HC). And, they are positively correlated with levels of serum anti-acetylcholine receptor antibody (anti-AchR Ab). It is unclear whether cTfh cell subset frequencies are altered and what role they play in MG patients. In order to clarify this, we examined the frequencies of cTfh cell counterparts, their subsets, and circulating plasmablasts in MG patients by flow cytometry. We determined the concentrations of serum anti-AChR Ab by enzyme-linked immunosorbent assay (ELISA). We assayed the function of cTfh cell subsets by flow cytometry and real-time polymerase chain reaction (RT-PCR). We found higher frequencies of cTfh cell counterparts, cTfh-Th17 cells, and plasmablasts in MG patients compared with HC. The frequencies of cTfh cell counterparts and cTfh-Th17 cells were positively correlated with the frequencies of plasmablasts and the concentrations of anti-AChR Ab in MG patients. Functional assays showed that activated cTfh-Th17 cells highly expressed key molecular features of Tfh cells including ICOS, PD-1, and IL-21. Results indicate that, just like cTfh cell counterparts, cTfh-Th17 cells may play a role in the immunopathogenesis and the production of anti-AChR Ab of MG.

The role of follicular T helper cells in patients with malignant lymphoid disease

OBJECTIVES

To investigate the dynamic change of follicular T helper cells (T_FH) in patients with malignant lymphoid disease (MLD) and to explore its clinical significance.

METHODS

The dynamic change of T_FH cells, ICOS⁺- and PD-1⁺ T_FH cells at pretreatment and different treatment periods was determined by flow cytometry in 85 MLD patients. Concentration of interleukin 21 (IL-21) was evaluated by ELISA, and the correlation between clinical prognosis and the ratio of T_FH cells was analyzed.

RESULTS

Significantly increased ICOS⁺- and PD-1⁺ T_FH cells were found in MLD patients at pretreatment compared to healthy controls. Decreased or even close to normal levels of ICOS⁺- and PD-1⁺ T_FH cells were found at the end of treatment. However, in the patients with progressive disease, high levels of ICOS⁺- and PD-1⁺ T_FH cells were found. Moreover, a significantly increased plasma IL-21 level was found in MLD patients. Negative correlation was found between the level of ICOS⁺-, PD-1⁺ T_FH cells, as well as IL-21 and the prognosis of MLD.

CONCLUSIONS

Significantly increased T_FH cell ratios were found in patients with MLD, and decreased T_FH cells ratios could be expected in those treatment-effective patients, which could be used as the therapeutic efficacy index.

Rapid de novo generation of antigen specific human B cells with expression of Blimp-1 and AID by in vitro immunization

In vitro immunization with antigens and cytokines triggers specific human B-cell response in short periods and is therefore superior to conventional in vivo immunization for antibody development. However, this new technology is limited by low efficiency, poor reproducibility, and requirement of pre-immunized lymphocytes. In this study, we demonstrate a novel method for de novo inducing antigen-specific human B cells in vitro. Unlike previous in vitro immunization of unfractionated PBMCs, we firstly optimized the conditions for inducing monocyte-derived dendritic cells (DCs) to efficiently capture, process, and present antigens. Instead of using the conventional method to activate Th2 cells for in vitro immunization, we succeeded to differentiate naïve CD4⁺ T cells into T follicular helper (Tfh) cells using antigen-sensitized DCs and cytokine cocktail. We discovered the differentiated T cells expressed ICOS, PD-1, BCL-6, and IL-21 at high levels. After 12 days of T-B co-culture, we observed induced T cells efficiently promoted naïve B cells to differentiate into plasmablasts secreting antigen-specific antibodies, with expression of Blimp-1 and AID related to affinity maturation and class switching. Thus, we established a new co-culture system with naïve lymphocyte populations for de novo acquisition of specifically in vitro immunized B cells potentially for development of therapeutic antibodies, which also provides novel insights into understanding the complex interactions among immune cells in lymph nodes.

Circulating CXCR5+CXCR3+PD-1lo Tfh-like cells in HIV-1 controllers with neutralizing antibody breadth

HIV-1-specific broadly neutralizing antibodies (bnAbs) typically develop in individuals with continuous high-level viral replication and increased immune activation, conditions that cannot be reproduced during prophylactic immunization. Understanding mechanisms supporting bnAb development in the absence of high-level viremia may be important for designing bnAb-inducing immunogens. Here, we show that the breadth of neutralizing antibody responses in HIV-1 controllers was associated with a relative enrichment of circulating CXCR5⁺CXCR3⁺PD-1^lo CD4⁺ T cells. These CXCR3⁺PD-1^lo Tfh-like cells were preferentially induced in vitro by functionally superior dendritic cells from controller neutralizers, and able to secrete IL-21 and support B cells. In addition, these CXCR3⁺PD-1^lo Tfh-like cells contained higher proportions of stem cell-like memory T cells, and upon antigenic stimulation differentiated into PD-1^hi Tfh-like cells in a Notch-dependent manner. Together, these data suggest that CXCR5⁺CXCR3⁺PD-1^lo cells represent a dendritic cell-primed precursor cell population for PD-1^hi Tfh-like cells that may contribute to the generation of bnAbs in the absence of high-level viremia.

Regulators of Tfh Cell Differentiation

The follicular helper T (Tfh) cells help is critical for activation of B cells, antibody class switching, and germinal center (GC) formation. The Tfh cells are characterized by the expression of CXC chemokine receptor 5 (CXCR5), ICOS, programed death 1 (PD-1), B cell lymphoma 6 (BCL-6), and IL-21. They are involved in clearing infections and are adversely linked with autoimmune diseases and also have a role in viral replication as well as clearance. On the one hand, Tfh cells are generated from naive CD4⁺ T cells with sequential steps involving cytokine signaling (IL-21, IL-6, IL-12, activin A), migration, and positioning in the GC by CXCR5, surface receptors (ICOS/ICOSL, signaling lymphocyte activation molecule-associated protein/signaling lymphocyte activation molecule) as well as transcription factor (BCL-6, c-Maf, and signal transducer and activator of transcription 3) signaling and repressor miR155. On the other hand, Tfh generation is negatively regulated at specific steps of Tfh generation by specific cytokine (IL-2, IL-7), surface receptor (PD-1, CTLA-4), transcription factors B lymphocyte maturation protein 1, signal transducer and activator of transcription 5, T-bet, KLF-2 signaling, and repressor miR 146a. Interestingly, miR-17-92 and FOXO1 act as a positive as well as a negative regulator of Tfh differentiation depending on the time of expression and disease specificity. Tfh cells are also generated from the conversion of other effector T cells as exemplified by Th1 cells converting into Tfh during viral infection. The mechanistic details of effector T cells conversion into Tfh are yet to be clear. To manipulate Tfh cells for therapeutic implication and or for effective vaccination strategies, it is important to know positive and negative regulators of Tfh generation. Hence, in this review, we have highlighted and interlinked molecular signaling from cytokines, surface receptors, transcription factors, ubiquitin ligase, and microRNA as positive and negative regulators for Tfh differentiation.

Distinct phenotypic subpopulations of circulating CD4+CXCR5+ follicular helper T cells in children with active IgA vasculitis

Background

Circulating follicular helper T (Tfh) cells are a heterogeneous population of CD4⁺ helper T cells that promotes pathogenic immune responses in autoimmune diseases. In this study, we examined the status of different subpopulations of Tfh cells in peripheral circulation and their associations with various clinical characteristics of IgA vasculitis (IgAV).

Methods

According to the phenotypic expressions of different molecules, focus was given on six subpopulations of Tfh cells: CD4⁺CXCR5⁺, CD4⁺CXCR5⁺ICOS⁺, CD4⁺CXCR5⁺ICOS⁺PD-1⁺, CD4⁺CXCR5⁺ICOS^highPD-1^high, CD4⁺CXCR5⁺ICOS⁻PD-1⁺, and CXCR5⁺CD45RA⁻IL-21⁺. The frequencies of these six subpopulations and the circulating level of Tfh-related cytokine interleukin 21 (IL-21) were measured from 27 patients with IgAV and 15 healthy controls (HC) by flow cytometry and flow cytometric bead array, respectively.

Results

Significantly higher frequencies of CD4⁺CXCR5⁺, CD4⁺CXCR5⁺ICOS⁺, CD4⁺CXCR5⁺ICOS⁺PD-1⁺, CD4⁺CXCR5⁺ICOS^highPD-1^high and CXCR5⁺CD45RA⁻IL-21⁺ Tfh cells, as well as higher levels of plasma IL-21, were detected in IgAV patients compared to HC. The level of each Tfh subpopulation varied by the presenting symptoms of IgAV, but did not differ between patients treated or not treated with glucocorticoids. When the disease entered the remission stage following treatment, circulating levels of CD4⁺CXCR5⁺, CD4⁺CXCR5⁺ICOS⁺, CD4⁺CXCR5⁺ICOS⁺PD-1⁺, CD4⁺CXCR5⁺ICOS^highPD-1^high and CXCR5⁺CD45RA⁻IL-21⁺ Tfh cells, as well as plasma IL-21 levels were reduced. Among the six subpopulations of Tfh cells, both CD4⁺CXCR5⁺ICOS⁺ and CXCR5⁺CD45RA⁻IL-21⁺ significantly and positively correlated with serum IgA and plasma IL-21 levels, but only CXCR5⁺CD45RA⁻IL-21⁺ significantly and negatively correlated with the serum C4 level.

Conclusions

Tfh cells may differentially contribute to the development of IgAV or predict disease progression. These findings provide novel insights in the pathogenesis of IgAV and may benefit treatment development targeting organ-specific presenting symptoms of IgAV.

Altered circulating T follicular helper cell subsets in patients with psoriasis vulgaris

Circulating T follicular helper (Tfh) cells in the blood are counterparts to conventional Tfh cells in germinal centres. Similarly to conventional Tfh cells, circulating Tfh cells provide helpful signals for B cells. Circulating Tfh cells can be divided into three subpopulations, including Tfh17 (CXCR3-CCR6+), Tfh1 (CXCR3+CCR6-), and Tfh2 (CXCR3-CCR6-) cells, based on differences in CXCR3 and CCR6 expression. Recent studies have demonstrated that alterations in circulating Tfh cell subsets have significant effects on the progression of numerous autoimmune diseases. To address the role of circulating Tfh cells in psoriasis, we used flow cytometry to analyse frequencies of circulating Tfh cell subsets and levels of IL-21 receptor (IL-21R) expression on B cells in 32 patients with psoriasis vulgaris and 13 sex- and age-matched healthy controls. We observed dynamic changes in Tfh17 cell frequency and disease severity in 10 psoriasis patients during a 6-month treatment. Our results demonstrate that the frequency of Tfh17 cells was significantly increased in psoriasis patients and was positively correlated with psoriasis area and severity index (PASI) score, a marker of disease severity (P<0.05). During the follow-up period, the frequencies of Tfh17 cells decreased, and reductions in PASI scores were observed. Moreover, IL-21R expression on B cells was significantly increased in patients with psoriasis vulgaris (P<0.05). Interestingly, IL-21R levels on B cells were correlated with both PASI score and the frequency of Tfh17 cells (P<0.05). In conclusion, this study is the first investigation of the distribution of circulating Tfh subsets in psoriasis. These results deepen our understanding of the immune state of psoriasis patients. Our data also indicate that Tfh17 cells may not be good biomarkers for diagnosing psoriasis but may be potential biomarkers of disease severity in psoriasis.

Identification of tonsillar CD4+CD25-LAG3+ T cells as naturally occurring IL-10-producing regulatory T cells in human lymphoid tissue

IL-10-producing regulatory T cells (IL-10-producing Tregs) are one of the regulatory T cell subsets characterized by the production of high amounts of IL-10, the lack of FOXP3 expression and the strong immunosuppressive capabilities. IL-10-producing Tregs have been primarily reported as induced populations thus far, in part because identifying naturally occurring IL-10-producing Tregs was difficult due to the lack of definitive surface markers. Lymphocyte-activation gene 3 (LAG3) is a CD4 homologue that we have identified as being expressed on IL-10 producing Tregs. In human PBMC, LAG3 combined with CD49b efficiently identifies IL-10-producing Tregs. However, naturally occurring IL-10-producing Tregs in human secondary lymphoid tissue have not been described. In this report, we identified CD4⁺CD25^-LAG3⁺ T cells in human tonsil. This T cell subset produced high amounts of IL-10 and expressed low levels of FOXP3. Surface markers and microarray analysis revealed that this is a distinct tonsillar CD4⁺ T cell subset. CD4⁺CD25^-LAG3⁺ T cells expressed interleukin 10 (IL10), PR/SET domain 1 (PRDM1), and CD274 at high levels and chemokine receptor 5 (CXCR5) at low levels. CD4⁺CD25^-LAG3⁺ T cells suppressed antibody production more efficiently than CD4⁺CD25⁺ T cells, and CD4⁺CD25^-LAG3⁺ T cells induced B cell apoptosis. Moreover, analysis of humanized mice revealed that this cell subset suppressed a graft-versus-host disease (GVHD) reaction in vivo. Our study reveals the existence of naturally occurring IL-10-producing Tregs in human secondary lymphoid tissue and their function in immune regulation.

Gene expression profile analysis in response to α1,2-fucosyl transferase (FUT1) gene transfection in epithelial ovarian carcinoma cells

The aim of this study was to identify differentially expressed genes (DEGs) in response to α1,2-fucosyl transferase (FUT1) gene transfection in epithelial ovarian cancer cells. Human whole-genome oligonucleotide microarrays were used to determine whether gene expression profile may differentiate the epithelial ovarian cell line Caov-3 transfected with FUT1 from the empty plasmid-transfected cells. Quantitative real-time PCR and immunohistochemical staining validated the microarray results. Gene expression profile identified 215 DEGs according to the selection criteria, in which 122 genes were upregulated and 93 genes were downregulated. Gene Ontology (GO) and canonical pathway enrichment analysis were applied, and we found that these DEGs are involved in BioCarta mammalian target of rapamycin (mTOR) pathway, BioCarta eukaryotic translation initiation factor 4 (EIF4) pathway, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in cancer. Interaction network analysis predicted genes participating in the regulatory connection. Highly differential expression of TRIM46, PCF11, BCL6, PTEN, and FUT1 genes was validated by quantitative real-time PCR in two cell line samples. Finally, BCL6 and Lewis Y antigen were validated at the protein level by immunohistochemistry in 103 paraffin-embedded ovarian cancer tissues. The identification of genes in response to FUT1 may provide a theoretical basis for the investigations of the molecular mechanism of ovarian cancer.

Early Rise of Blood T Follicular Helper Cell Subsets and Baseline Immunity as Predictors of Persisting Late Functional Antibody Responses to Vaccination in Humans

CD4⁺ T follicular helper cells (T_FH) have been identified as the T-cell subset specialized in providing help to B cells for optimal activation and production of high affinity antibody. We recently demonstrated that the expansion of peripheral blood influenza-specific CD4⁺IL-21⁺ICOS1⁺ T helper (T_H) cells, three weeks after vaccination, associated with and predicted the rise of protective neutralizing antibodies to avian H5N1. In this study, healthy adults were vaccinated with plain seasonal trivalent inactivated influenza vaccine (TIIV), MF59^®-adjuvanted TIIV (ATIIV), or saline placebo. Frequencies of circulating CD4⁺ T_FH1 ICOS⁺ T_FH cells and H1N1-specific CD4⁺IL-21⁺ICOS⁺ CXCR5⁺ T_FH and CXCR5^- T_H cell subsets were determined at various time points after vaccination and were then correlated with hemagglutination inhibition (HI) titers. All three CD4+ T cell subsets expanded in response to TIIV and ATIIV, and peaked 7 days after vaccination. To demonstrate that these T_FH cell subsets correlated with functional antibody titers, we defined an alternative endpoint metric, decorrelated HI (DHI), which removed any correlation between day 28/day 168 and day 0 HI titers, to control for the effect of preexisting immunity to influenza vaccine strains. The numbers of total circulating CD4⁺ T_FH1 ICOS⁺ cells and of H1N1-specific CD4⁺IL-21⁺ICOS⁺ CXCR5⁺, measured at day 7, were significantly associated with day 28, and day 28 and 168 DHI titers, respectively. Altogether, our results show that CD4⁺ T_FH subsets may represent valuable biomarkers of vaccine-induced long-term functional immunity.

Anti-CD28 Antibody and Belatacept Exert Differential Effects on Mechanisms of Renal Allograft Rejection

Belatacept is a biologic that targets CD80/86 and prevents its interaction with CD28 and its alternative ligand, cytotoxic T lymphocyte antigen 4 (CTLA-4). Clinical experience in kidney transplantation has revealed a high incidence of rejection with belatacept, especially with intensive regimens, suggesting that blocking CTLA-4 is deleterious. We performed a head to head assessment of FR104 (n=5), a selective pegylated Fab' antibody fragment antagonist of CD28 that does not block the CTLA-4 pathway, and belatacept (n=5) in kidney allotransplantation in baboons. The biologics were supplemented with an initial 1-month treatment with low-dose tacrolimus. In cases of acute rejection, animals also received steroids. In the belatacept group, four of five recipients developed severe, steroid-resistant acute cellular rejection, whereas FR104-treated animals did not. Assessment of regulatory T cell-specific demethylated region methylation status in 1-month biopsy samples revealed a nonsignificant trend for higher regulatory T cell frequencies in FR104-treated animals. Transcriptional analysis did not reveal significant differences in Th17 cytokines but did reveal higher levels of IL-21, the main cytokine secreted by CD4 T follicular helper (Tfh) cells, in belatacept-treated animals. In vitro, FR104 controlled the proliferative response of human preexisting Tfh cells more efficiently than belatacept. In mice, selective CD28 blockade also controlled Tfh memory cell responses to KLH stimulation more efficiently than CD80/86 blockade. Our data reveal that selective CD28 blockade and belatacept exert different effects on mechanisms of renal allograft rejection, particularly at the level of Tfh cell stimulation.

Bob1 limits cellular frequency of T-follicular helper cells

T follicular helper (Tfh) cells are involved in specific humoral immunity at initial and recall phases. The fact that the transcription repressors B‐cell lymphoma‐6 and Blimp‐1 determine lineages of Tfh cells and other types of effector CD4⁺ T cells, respectively, suggests that there are unique mechanisms to establish Tfh‐cell identity. In this study, we found that Tfh cells preferentially express the transcriptional coactivator Bob1. Bob1 of Tfh cells was dispensable for the expression of B‐cell lymphoma‐6 and the functional property of the cells for B cell help. However, upon initial immunization of foreign antigens, the percentages of Tfh cells in Bob1^−/− mice were much higher than those in wild‐type (WT) mice. In addition, expansion of Tfh cells within Bob1^−/−CD4⁺ T cells transferred into WT mice revealed that the high frequency of Tfh cells was caused by a T‐cell‐intrinsic mechanism. These findings were further supported by the results of in vitro studies demonstrating that Bob1^−/− Tfh cells had greater proliferative activity in response to stimuli by CD3/CD28 monoclonal antibody and were also refractory to CD3‐induced cell death in comparison to WT Tfh cells. These results suggest that Tfh cells harbor a Bob1‐related mechanism to restrict numerical frequency against stimulation of TCRs.

Human Circulating T Follicular Helper Cell Subsets in Health and Disease

T follicular helper (Tfh) cells are specialized to provide help to B cells and to induce durable antibody response. Our knowledge on the biology of Tfh cells and their contribution to disease has significantly increased in the past decade. In particular, recent discoveries of functionally distinct subsets within circulating Tfh (cTfh) cells in human blood have provided clues to assess the ongoing Tfh responses in healthy subjects after vaccinations and in patients with autoimmune diseases. The immune pathways associated with Tfh cell differentiation in humans are also getting revealed. In this review, I will first summarize the subsets within human cTfh cells, and discuss their alterations in patients with autoimmune diseases. Then I will discuss the mechanisms associated with the aberrant Tfh responses in human autoimmune diseases.

Early Loss of Splenic Tfh Cells in SIV-Infected Rhesus Macaques

Follicular T helper cells (Tfh), a subset of CD4 T lymphocytes, provide crucial help to B cells in the production of antigen-specific antibodies. Although several studies have analyzed the dynamics of Tfh cells in peripheral blood and lymph nodes (LNs) during Aids, none has yet addressed the impact of SIV infection on the dynamics of Tfh cells in the spleen, the primary organ of B cell activation. We show here a significant decrease in splenic Tfh cells in SIVmac251-infected rhesus macaques (RMs) during the acute phase of infection, which persists thereafter. This profound loss is associated with lack of sustained expression of the Tfh-defining transcription factors, Bcl-6 and c-Maf but with higher expression of the repressors KLF2 and Foxo1. In this context of Tfh abortive differentiation and loss, we found decreased percentages of memory B cell subsets and lower titers of SIV-specific IgG. We further demonstrate a drastic remodeling of the lymphoid architecture of the spleen and LNs, which disrupts the crucial cell-cell interactions necessary to maintain memory B cells and Tfh cells. Finally, our data demonstrated the early infection of Tfh cells. Paradoxically, the frequencies of SIV DNA were higher in splenic Tfh cells of RMs progressing more slowly suggesting sanctuaries for SIV in the spleen. Our findings provide important information regarding the impact of HIV/SIV infection on Tfh cells, and provide new clues for future vaccine strategies.

Higher Frequency of CD4+CXCR5+ICOS+PD1+ T Follicular Helper Cells in Patients With Infectious Mononucleosis

Follicular helper T (Tfh) cells are recognized as a distinct CD4helper T cell subset, and mainly dysregulated in the autoimmune disease, whether it plays a role in the infectious mononucleosis (IM) diseases is unknown. In this study, we found that the CD4CXCR5 Tfh cells were not significantly changed, but the CD4CXCR5ICOS and CD4CXCR5ICOSPD1 Tfh subsets were significantly increased in the IM patients, and all these cells were significantly changed after antiviral therapy. Second, only the numbers of CD4CXCR5ICOSPD1 Tfh cells correlated with the Epstein-Barr virus (EBV) DNA load, negatively correlated with the numbers of naive B cells and amount of IL-21, and positively correlated with the numbers of plasma cells, memory B cells, and atypical lymphocytes. Third, the frequency of CD4CXCR5ICOSPD1 Tfh subset was significantly higher in lymphadenectasis or hepatosplenomegaly patients, and associated with the level of alanine aminotransferase (ALT). All together, our findings discovered this CD4CXCR5ICOSPD1 Tfh cell subset might play an important role in the pathogenesis of IM.

Adenoidal follicular T helper cells provide stronger B-cell help than those from tonsils

OBJECTIVES/HYPOTHESIS

The tonsils and adenoids are secondary lymphoid organs, where antigen processing and immune cell development occur to control bacterial colonization and infection in the upper respiratory tract. Both organs are abundant in follicular T helper cells (TFH), a subset of T cells specialized for promoting B-cell development. There are no prior studies on differences between the immune cells of the tonsils and adenoids and whether the cells function differently.

STUDY DESIGN

In vitro assays to assess cell phenotype of tonsils and adenoids from young children (median age = 40 months).

METHODS

Mononuclear cells from tonsils and adenoids were cultured with or without 1 µg/mL Staphylococcus enterotoxin B (SEB) for 4 days. Cell phenotype and function were assessed by flow cytometry and multiplex enzyme-linked immunosorbent assay.

RESULTS

We found that in resting adenoids, TFH expressed higher CXCR5 and inducible costimulator but lower PD-1 than those from the tonsils, and that adenoidal B cells expressed higher CD27. Upon polyclonal stimulation with SEB, both TFH and B cells from the adenoids proliferated to a greater extent, and culture supernatants contained higher levels of interleukin 21.

CONCLUSIONS

We conclude that the cells of the adenoid are disposed toward the provision of more robust B-cell help than the tonsils.

LEVEL OF EVIDENCE

NA.

CCR7(lo)PD-1(hi) CXCR5(+) CD4(+) T cells are positively correlated with levels of IL-21 in active and transitional cystic echinococcosis patients

Background

In our study, we investigated whether circulating T follicular helper (Tfh) and the related cytokines are involved in human cystic echinococcosis (CE).

Methods

A total of 64 patients with CE and 30 healthy controls were enrolled in this study. Percentages of CCR7^loPD-1^hi cells within CXCR5⁺ CD4⁺ T cells (circulating Tfh cells) were detected by flow cytometry. Levels of IL-21 and IL-4 in peripheral blood were detected by cytometric bead array. The mRNA expression of IL-21, IL-4, Bcl-6, and Blimp-1 in peripheral blood mononuclear cells (PBMCs) were measured by real-time PCR. Levels of IgG1, IgG2, IgG3, and IgG4 in the patients’ sera were measured using enzyme-linked immunosorbent assay.

Results

Percentages of circulating Tfh cells were significantly increased in the CE1, CE2, and CE3 groups (p < 0.05). The concentrations of IL-21 and IL-4 in the serum were significantly increased in CE1, CE2, and CE3 groups (p < 0.05). IL-21 was positively correlated with circulating Tfh cells in CE3 group (r = 0.779, p < 0.05). The mRNA levels of IL-21, IL-4, and Bcl-6 were increased in CE1, CE2, and CE3 groups. Levels of IgG1 and IgG4 in patients’ sera were increased in CE1, CE2, and CE3 groups. Levels of IgG2 and IgG3 were increased in CE4-5 group. Additionally, after stimulation with hydatid fluid in vitro, the levels of circulating Tfh cells, IL-21 and IL-4 in PBMCs isolated from CE patients were significantly increased (p < 0.05).

Conclusions

The levels of circulating Tfh and related cytokines were significantly increased in CE patients, suggesting that they are involved in human CE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1156-9) contains supplementary material, which is available to authorized users.

Nasal IL-4(+)CXCR5(+)CD4(+) T follicular helper cell counts correlate with local IgE production in eosinophilic nasal polyps

BACKGROUND

Locally produced IgE contributes to the initiation and development of eosinophilic inflammation in eosinophilic nasal polyps independent of systemic atopy. However, whether CXCR5(+)CD4(+) T follicular helper (TFH) cells are involved in local IgE production at mucosal sites remains unexplored.

OBJECTIVE

We sought to explore the presence, phenotype, and function of CXCR5(+)CD4(+) TFH cells in eosinophilic nasal polyp tissues compared with noneosinophilic nasal polyp and control normal nasal tissues.

METHODS

TFH cell-surface phenotypes and subsets and B-cell subsets in nasal tissues and peripheral blood were studied by means of flow cytometry. Immunohistochemistry was used to detect the tissue location of TFH cells. Sorted nasal TFH cells and CXCR5(-) T cells were cultured with autologous naive B cells purified from blood.

RESULTS

Nasal TFH cells expressed inducible costimulator, programmed cell death protein 1, and the transcription factor B-cell lymphoma 6 (Bcl-6) at an intermediate level when compared with bona fide TFH cells in tonsils and circulating TFH cells. Although counts of total TFH cells and IL-21(+), IFN-γ(+), and IL-17(+) TFH cells were increased in both eosinophilic and noneosinophilic nasal polyp tissues compared with those in normal nasal tissues, IL-4(+) TFH cell counts were only increased in eosinophilic polyp tissues. IL-4 and IL-21 were involved in polyp TFH cell-induced IgE production from naive B cells, and nasal IL-4(+) TFH cell counts correlated highly with local IgE levels in vivo. IL-4(+)Bcl-6(+)CD4(+) TFH cells were identified in ectopic lymphoid structures in eosinophilic nasal polyps. TFH cells also positively correlated with germinal center B cells and plasma cells in nasal tissues.

CONCLUSION

Nasal IL-4(+) TFH cells might be involved in local IgE production in eosinophilic nasal polyps.

Development and function of follicular helper T cells

Most currently available vaccines rely on the induction of long-lasting protective humoral immune responses by memory B cells and plasma cells. Antibody responses against most antigens require interactions between antigen-specific B cells and CD4(+) T cells. Follicular helper T cells (TFH cells) are specialized subset of T cells that provide help to B cells and are essential for germinal center formation, affinity maturation, and the development of high-affinity antibodies. TFH-cell differentiation is a multistage process involving B-cell lymphoma 6 and other transcription factors, cytokines, and costimulation through inducible costimulator (ICOS) and several other molecules. This article reviews recent advances in our understanding of TFH cell biology, including their differentiation, transcriptional regulation, and function.

OX40 Ligand Contributes to Human Lupus Pathogenesis by Promoting T Follicular Helper Response

Increased activity of T follicular helper (Tfh) cells plays a major pathogenic role in systemic lupus erythematosus (SLE). However, the mechanisms that cause aberrant Tfh cell responses in SLE remain elusive. Here we showed the OX40 ligand (OX40L)-OX40 axis contributes to the aberrant Tfh response in SLE. OX40L was expressed by myeloid antigen-presenting cells (APCs), but not B cells, in blood and in inflamed tissues in adult and pediatric SLE patients. The frequency of circulating OX40L-expressing myeloid APCs positively correlated with disease activity and the frequency of ICOS(+) blood Tfh cells in SLE. OX40 signals promoted naive and memory CD4(+) T cells to express multiple Tfh cell molecules and were sufficient to induce them to become functional B cell helpers. Immune complexes containing RNA induced OX40L expression on myeloid APCs via TLR7 activation. Our study provides a rationale to target the OX40L-OX40 axis as a therapeutic modality for SLE.

IL-33 Enhances Humoral Immunity Against Chronic HBV Infection Through Activating CD4(+)CXCR5(+) TFH Cells

This study aimed to investigate the potential effect of interleukin 33 (IL-33) on humoral responses to hepatitis B virus (HBV) and the possible mechanisms underlying the action of IL-33 in regulating follicular helper T (TFH) cells. The impact of IL-33 treatment on the levels of serum HBV DNA, HBsAg, HBeAg, HBsAb, and HBeAb, as well as the frequencies of CD4(+)CXCR5(+) TFH cells in wild-type HBV transgenic (HBV-Tg) mice and in a transwell coculture of HepG2.2.15 with IL-33-treated peripheral blood mononuclear cells (PBMCs) were determined. Furthermore, the gene transcription profiles in IL-33-treated TFH cells were determined by microarrays. IL-33 treatment significantly reduced the levels of serum HBV DNA, HBsAg, and HBeAg, but increased the levels of HBsAb and HBeAb in HBV-Tg mice, accompanied by increased frequency of splenic infiltrating CD4(+)CXCR5(+) TFH cells in HBV-Tg. Similarly, coculture of HepG2.2.15 cells with IL-33-treated PBMCs reduced the levels of HBV DNA, HBsAg, and HBeAg, but increased the levels of HBsAb and HBeAb. Microarray analyses indicated that IL-33 significantly modulated the transcription of many genes involved in regulating TFH activation and differentiation. Our findings suggest that IL-33 may activate TFH cells, promoting humoral responses to HBV during the pathogenic process.

Pathophysiology of T follicular helper cells in humans and mice

Follicular helper T cells (TFH cells) compose a heterogeneous subset of CD4(+) T cells that induce the differentiation of B cells into plasma cells and memory cells. They are found within and in proximity to germinal centers in secondary lymphoid organs, and their memory compartment also circulates in the blood. Our knowledge on the biology of TFH cells has increased significantly during the past decade, largely as a result of mouse studies. However, recent studies on human TFH cells isolated from lymphoid organ and blood samples and recent observations on the developmental mechanism of human TFH cells have revealed both similarities and differences between human and mouse TFH cells. Here we present the similarities and differences between mouse and human lymphoid organ-resident TFH cells and discuss the role of TFH cells in response to vaccines and in disease pathogenesis.

Circulating follicular helper-like T cells in systemic lupus erythematosus: association with disease activity

OBJECTIVE

To assess circulating follicular helper T (Tfh)-like CD4+ T cells in patients with systemic lupus erythematosus (SLE) and determine their relationship to disease activity.

METHODS

Blood samples from patients with SLE, as well as blood samples from patients with Behçet's disease (BD) and healthy individuals as controls, were analyzed. In all samples, circulating Tfh-like cells were enumerated by flow cytometry, using, as markers, expression of CXCR5, inducible T cell costimulator (ICOS), and programmed death 1 (PD-1) protein, as well as secretion of interleukin-21 (IL-21). The frequency of circulating Tfh-like cells was compared to that of circulating plasmablasts (CD19+IgD-CD38+). In addition, the possible association of circulating Tfh-like cells with the SLE Disease Activity Index (SLEDAI) was evaluated.

RESULTS

The subset of circulating Tfh-like T cells, identified as CXCR5(high) ICOS(high) PD-1(high) , was expanded in the blood of SLE patients compared to controls. Circulating Tfh-like cells were found to produce IL-21 and had lower expression of CCR7 as compared to that in circulating CXCR5(high) central memory T cells, thereby enabling their distinction. Expression of PD-1, but not ICOS or CXCR5, was significantly elevated in circulating Tfh-like cells from SLE patients compared to controls. PD-1 expression among CXCR5(high) circulating Tfh-like cells correlated with the SLEDAI, frequency of circulating plasmablasts, and anti-double-stranded DNA antibody positivity, but not with disease duration or past organ injury; rather, this cell profile appeared to be a reflection of current active disease.

CONCLUSION

Circulating Tfh-like cells are associated with disease activity in SLE, suggesting that their presence indicates abnormal homeostasis of T cell-B cell collaboration, with a causal relationship that is central to disease pathogenesis. These findings also suggest that circulating Tfh-like cells provide a surrogate for aberrant germinal center activity in SLE, and that their PD-1 expression offers a tool for measuring disease activity and monitoring the response to therapies.

Increased circulating follicular helper T cells and activated B cells correlate with disease severity in patients with psoriasis

BACKGROUND

Follicular Helper T (TFH) Cells are a population of recently discovered CD4(+) T cells involved in autoimmune diseases. However, the contribution of TFH cells in patients with psoriasis remains unknown.

OBJECTIVE

We aimed to investigate the levels of TFH cells, B cells and their clinical relevance in patients with psoriasis.

METHODS

Using multi-colour flow cytometry, we detected different subsets of TFH cells and B cells in the peripheral blood of 27 patients with psoriasis and 13 healthy donors. Serum IL-21 levels were measured by ELISA. The relationship between the levels of TFH cells, IL-21, B cells and disease severity were analysed.

RESULTS

Compared with healthy donors, higher levels of circulating CD3(+) CD4(+) CXCR5(+) cells, CD3(+) CD4(+) CXCR5(+) ICOS(+), CD3(+) CD4(+) CXCR5(+) PD-1(+), CD3(+) CD4(+) CXCR5(+) ICOS(+) PD-1(+) TFH cells and CD19(+) IgD(+) CD27(-) naive B, CD19(+) CD86(+) activated B, but lower levels of CD19(+) IgD(+) CD27(+) preswitch and CD19(+) IgD(-) CD27(+) postswitch memory B cells, were observed in patients with psoriasis. In addition, serum IL-21 levels in patients with psoriasis were significantly higher than those in healthy donors, and showed to be positively correlated with the levels of different subsets of TFH cells, and the level of CD19(+) CD86(+) B cells was also correlated with TFH cells and IL-21 levels. Furthermore, a significant correlation was found between the levels of CD3(+) CD4(+) CXCR5(+) ICOS(+) TFH cells, CD3(+) CD4(+) CXCR5(+) ICOS(+) PD-1(+) TFH cells, CD19(+) CD86(+) B cells and IL-21 with Psoriasis Area and Severity Index scores.

CONCLUSION

The levels of TFH cells and activated B cells were increased in the peripheral blood of patients with psoriasis, and positively correlated with disease severity. These results suggest that TFH cells and activated B cells may play a role in the pathogenesis of psoriasis.

Beneficial effect of T follicular helper cells on antibody class switching of B cells in prostate cancer

Prostate cancer is the most common malignancy in males and easily develops to be aggressive which is closely related to the chronic inflammatory tumor microenvironment in situ. This study aimed to assess the immunoglobulin G (IgG) subclass of B cells and explore their interactions with T follicular helper (Tfh) subsets in prostate cancer patients. The percentages of peripheral blood naïve B cells, memory B cells and mature B cells, as well as Tfh1, Tfh2 and Tfh17 cells were analyzed or sorted by FACSAria. The ratios of the different IgG subclasses (IgG1, IgG2, IgG3 and IgG4) were detected by ELISA, and the expression levels of CXCR3 and CCR6 were measured using RT-PCR and western blot analysis. Meanwhile a co-culture system of B and Tfh cells was to assess the effect of each Tfh subset on the antibody subclass switching of B cells in vitro. We observed higher percentages of 3 Tfh subsets and IgG4+ B cells in the patients with prostate cancer than that in the health controls and proved a positive correlation between Tfh2 and IgG4+ B cells. Then we verified that IL-4, IL-6, IL-10 and prostaglandin E2 (PGE2) effectively promoted antibody class switching of B cells, which may be mediated by inducing Tfh2 cells, yet the study was not completely dependent on Tfh cells. The results provide evidence of the B cell response to an immune suppressive environment by evaluating IgG4 antibodies, and established a relationship between IgG4+ B cells and Tfh2 cells. Clarification of lymphocyte functions in the inflammatory microenvironment of tumors will be of potential therapeutic value.

CD25(+) Bcl6(low) T follicular helper cells provide help to maturing B cells in germinal centers of human tonsil

The majority of CXCR5(+) PD1(+) CD4(+) T follicular helper (Tfh) cells (>90%) are CD25(-) Bcl6(hi) , while a small subpopulation (<10%) are CD25(+) Bcl6(low) but do not express FoxP3 and are not T regulatory cells. We purified T:B-cell conjugates from tonsils and found they were enriched for the CD25(+) Bcl6(low) Tfh-cell subpopulation. In response to IL-2, these CD25(+) Tfh cells increased expression of costimulatory molecules ICOS or OX40, upregulated transcription factor cMaf, produced cytokines IL-21, IL-17, and IL-10, and raised the levels of antiapoptotic protein Bcl2. Conjugates formed with CD25(+) BCl6(low) Tfh cells included B cells expressing higher levels of activation-induced cytidine deaminase (AID), memory marker CD45RO, surface IgG or IgA, and MHC class II compared to B-cell conjugates including CD25(-) Bcl6(hi) Tfh cells. While IL-2 suppresses early Tfh-cell differentiation, Tfh-cell recognition of antigen-presenting B cells and signaling through the T-cell receptor likely triggers expression of the high-affinity IL-2 receptor and responses to IL-2 including downregulation of Bcl6. CD25 expression on Tfh cells and local production of IL-2 in tonsil or lymph node may support B helper T-cell function during later stages of B-cell maturation and the development of immune memory.

Splenic TFH expansion participates in B-cell differentiation and antiplatelet-antibody production during immune thrombocytopenia

Antiplatelet-antibody-producing B cells play a key role in immune thrombocytopenia (ITP) pathogenesis; however, little is known about T-cell dysregulations that support B-cell differentiation. During the past decade, T follicular helper cells (TFHs) have been characterized as the main T-cell subset within secondary lymphoid organs that promotes B-cell differentiation leading to antibody class-switch recombination and secretion. Herein, we characterized TFHs within the spleen of 8 controls and 13 ITP patients. We show that human splenic TFHs are the main producers of interleukin (IL)-21, express CD40 ligand (CD154), and are located within the germinal center of secondary follicles. Compared with controls, splenic TFH frequency is higher in ITP patients and correlates with germinal center and plasma cell percentages that are also increased. In vitro, IL-21 stimulation combined with an anti-CD40 agonist antibody led to the differentiation of splenic B cells into plasma cells and to the secretion of antiplatelet antibodies in ITP patients. Overall, these results point out the involvement of TFH in ITP pathophysiology and the potential interest of IL-21 and CD40 as therapeutic targets in ITP.

Genetic polymorphisms of CXCR5 and CXCL13 are associated with non-responsiveness to the hepatitis B vaccine

A cohort based study has been undertaken to investigate the possible association of genetic polymorphisms in genes functionally related to follicular T helper (TfH) cells with non-responsiveness to hepatitis B virus (HBV) vaccination. A total of 24 single nucleotide polymorphisms (SNPs) in 6 TfH related genes (CXCR5, ICOS, CXCL13, IL-21, BCL6 and CD40L) were investigated in 20 non-responders and 45 responders to HBV vaccination. Genetic association analysis revealed that three SNPs (rs497916, rs3922, rs676925) in CXCR5 and one SNP (rs355687) in CXCL13 were associated with hepatitis B vaccine efficacy. In addition, significantly unbalanced distributions of two haplotypes, defined by three SNPs (rs497916, rs3922, rs676925) within CXCR5, were also seen between non-responders and responders. Furthermore, we demonstrated that the rs3922 "GG" genotype was associated with higher levels of CXCR5 than the "AG" and "AA" genotype in a group of healthy volunteers. A dual luciferase report assay was used to confirm that the "G" allele in rs3922 may lead to higher gene expression than the "A" allele, implicating that rs3922 might be a functional SNP affecting CXCR5 expression. These results indicated that polymorphism associated changes in CXCR5 expression in TfH cells may be associated with non-responsiveness to hepatitis B vaccination.

The cytokine TGF-β co-opts signaling via STAT3-STAT4 to promote the differentiation of human TFH cells

Understanding the developmental mechanisms of T follicular helper (T_FH) cells in humans is a highly relevant topic to clinic. However, factors that drive human CD4⁺ helper T (T_H) cell differentiation program towards T_FH cells remain largely undefined. Here we show that TGF-β provides critical additional signals for the transcription factors STAT3 and STAT4 to promote the initial T_FH differentiation programs in humans. This mechanism does not appear to be shared with mouse T_H cells. The developing human Bcl-6⁺ T_FH cells also expressed RORγt, a transcription factor typically expressed by T_H17 cells. Our study documents a mechanism by which T_FH and T_H17 cells co-emerge in inflammatory environments in humans, as often observed in many human autoimmune diseases.

Phenotype and functions of memory Tfh cells in human blood

Our understanding of the origin and functions of human blood CXCR5(+) CD4(+) T cells found in human blood has changed dramatically in the past years. These cells are currently considered to represent a circulating memory compartment of T follicular helper (Tfh) lineage cells. Recent studies have shown that blood memory Tfh cells are composed of phenotypically and functionally distinct subsets. Here, we review the current understanding of human blood memory Tfh cells and the subsets within this compartment. We present a strategy to define these subsets based on cell surface profiles. Finally, we discuss how increased understanding of the biology of blood memory Tfh cells may contribute insight into the pathogenesis of autoimmune diseases and the mode of action of vaccines.

Loss of circulating CD4 T cells with B cell helper function during chronic HIV infection

The interaction between follicular T helper cells (TFH) and B cells in the lymph nodes and spleen has a major impact on the development of antigen-specific B cell responses during infection or vaccination. Recent studies described a functional equivalent of these cells among circulating CD4 T cells, referred to as peripheral TFH cells. Here, we characterize the phenotype and in vitro B cell helper activity of peripheral TFH populations, as well as the effect of HIV infection on these populations. In co-culture experiments we confirmed CXCR5+ cells from HIV-uninfected donors provide help to B cells and more specifically, we identified a CCR7(high)CXCR5(high)CCR6(high)PD-1(high) CD4 T cell population that secretes IL-21 and enhances isotype-switched immunoglobulin production. This population is significantly decreased in treatment-naïve, HIV-infected individuals and can be recovered after anti-retroviral therapy. We found impaired immunoglobulin production in co-cultures from HIV-infected individuals and found no correlation between the frequency of peripheral TFH cells and memory B cells, or with neutralization activity in untreated HIV infection in our cohort. Furthermore, we found that within the peripheral TFH population, the expression level of TFH-associated genes more closely resembles a memory, non-TFH population, as opposed to a TFH population. Overall, our data identify a heterogeneous population of circulating CD4 T cells that provides in vitro help to B cells, and challenges the origin of these cells as memory TFH cells.

Neuropilin-1 expression characterizes T follicular helper (Tfh) cells activated during B cell differentiation in human secondary lymphoid organs

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.

CXCR5+CD4+ follicular helper T cells accumulate in resting human lymph nodes and have superior B cell helper activity

Although many relevant immune reactions are initiated in the lymph nodes, this compartment has not been systematically studied in humans. Analyses have been performed on immune cells derived from tonsils, but as this tissue is most often inflamed, generalization of these data is difficult. Here, we analyzed the phenotype and function of the human CD4(+) T-cell subsets and lineages in paired resting lymph node and peripheral blood samples. Naive, central memory cells and effector memory cells as well as Th1, Th2, Th17 and Treg cells were equally represented in both compartments. On the other hand, cytotoxic CD4(+) T cells were strikingly absent in the lymph nodes. CXCR5(+)CD4(+) T cells, representing putative follicular Th (Tfh) cells were over-represented in lymph nodes and expressed higher levels of Tfh markers than their peripheral blood counterparts. Compared with the circulating pool, lymph-node-derived CXCR5(+)CD4(+) T cells were superior in providing help to B cells. Thus, functionally competent Tfh cells accumulate in resting human lymph nodes, providing a swift induction of naive and memory antibody responses upon antigenic challenge.

High frequencies of activated B cells and T follicular helper cells are correlated with disease activity in patients with new-onset rheumatoid arthritis

This study aimed to examine the frequency of different subsets of circulating B and T follicular helper (Tfh) cells in patients with new-onset rheumatoid arthritis (RA) and following standard therapies. Twenty-five RA patients and 15 healthy controls (HC) were recruited for characterizing the frequency of CD27⁺, immunoglobulin (Ig)D⁺, CD86⁺, CD95⁺, Toll-like receptor (TLR)-9⁺ B cells and inducible T cell co-stimulator (ICOS) and programmed death 1 (PD-1)-positive Tfh cells and the level of serum interleukin (IL)-21. The potential correlation between the frequency of different subsets of B and Tfh cells and the values of clinical measures in RA patients was analysed. In comparison with HC, significantly higher percentages of circulating IgD⁺ CD27⁻ CD19⁺ naive B, CD86⁺ CD19⁺ and CD95⁺ CD19⁺ activated B, CD3⁺ CD4⁺ CXCR5⁺, CD3⁺ CD4⁺ CXCR5⁺ ICOS⁺, CD3⁺ CD4⁺ CXCR5⁺ PD-1⁺ and CD3⁺ CD4⁺ CXCR5⁺ ICOS⁺ PD-1⁺ Tfh cells but lower IgD⁺ CD27⁺ CD19⁺ preswitch memory B cells were detected, accompanied by significantly higher levels of serum IL-21 in the RA patients. Furthermore, the percentages of CD95⁺ B cells were correlated positively with the frequency of PD-1⁺ Tfh cells, but negatively with ICOS⁺ Tfh cells. The percentages of CD86⁺ B cells and ICOS⁺ Tfh cells were correlated positively with the values of disease activity score 28 (DAS28). Following the drug therapies for 1 month, the percentages of CD86⁺ B and PD-1⁺ Tfh cells were reduced significantly in the drug-responding patients. Our data suggest that activated B and Tfh cells may contribute to the pathogenesis of RA and the frequency of activated B and Tfh cells may be used as biomarkers for evaluating the therapeutic responses of individual patients with RA.