Exploring the prognostic value of T follicular helper cell levels in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) presents with heterogeneous clinical outcomes, suggesting varied underlying pathogenic mechanisms. This study aims to elucidate the impact of T follicular helper (Tfh) cells on CLL progression and prognosis. Gene expression profile data for CLL were collected from GSE22762 and GSE39671 datasets. Patients were divided into high and low groups using Tfh levels using the optimal cutoff value based on overall survival (OS) and time-to-first treatment (TTFT). Differential expression analysis was performed between these groups, followed by co-expression network analysis and single-sample Gene Set Enrichment Analysis (ssGSEA). Marker genes of Tfh cells were used to construct prognostic models. Additionally, 40 CLL patients were recruited and categorized based on median Tfh levels. Marker gene expression was assessed using RT-qPCR and Western Blot, and immune cell levels were determined through flow cytometry. The high group showed better prognosis compared to the low group. Among the 1121 differentially expressed genes identified, five co-expression networks were constructed, with the turquoise module showing the highest correlation with Tfh cells. Genes within this module significantly participate in cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, and natural killer cell mediated cytotoxicity. Tfh cells were significantly negatively correlated with activated B cells and positively correlated with Tregs. The Random Survival Forest (RSF) model identified 10 marker genes, and further analysis using Lasso regression and nomogram selected CLEC4A, RAE1, CD84, and PRDX1 as prognostic markers. In the high group, levels of CLEC4A and RAE1 were higher than in the low group, whereas CD84 and PRDX1 were lower. Flow cytometry revealed that the level of activated B cells in the high Tfh group was significantly lower than in the low Tfh group, while the level of Tregs is significantly higher in the high Tfh group. This study seeks to contribute to a more detailed understanding of the pathogenesis of CLL, delving into the prognostic significance of Tfh.

Clinical and prognostic significance of follicular helper and regulatory T cells in bladder cancer draining lymph nodes.

Follicular helper and regulatory T cells (Tfh/TFR) cells are distinct subsets of CD4+ cells that have been recognized for their critical role in regulating cellular reactions within the germinal centers of lymphoid follicles. In the present study, we aimed to determine the presence and the frequency of these cells in draining lymph nodes of patients with bladder cancer (BC). Forty-six patients with BC who had undergone radical cystectomy and pelvic lymph node dissection were enrolled. Following routine pathological examination, a portion of the dissected lymph nodes was minced to obtain a single-cell suspension. Mononuclear cells were then separated using Ficoll-Hypaque gradient centrifugation, and the samples with proper viability (> 95%) were subjected to further analysis. To phenotype the follicular subsets, cells were stained with appropriate fluorochrome-conjugated antibodies specific for CD4, CXCR5, BCL6, and FOXP3. The cells were then acquired on a four-color flow cytometer. The data were analyzed with the FlowJo software version 10.8.1 package. Our analysis indicated that, on average 37.89 ± 16.36% of CD4+ lymphocytes in draining lymph nodes of patients with BC expressed CXCR5. The majority of them were negative for FOXP3, representing helper subsets (28.73 ± 13.66). A small percent simultaneously expressed BCL6 transcription factor (1.65% ± 1.35), designated as Tfh (CD4+BCL6+CXCR5+FOXP3-). While less than 10% of CD4+ lymphocytes expressed CXCR5 and FOXP3, 1.78 ± 2.54 were also positive for BCL6, known as TFR. Statistical analysis revealed that the frequency of both Tfh and TFR cells was higher in draining lymph nodes of patients with tumor-infiltrated nodes (P = 0.035 and P = 0.079, respectively) compared to those with negative ones. The percentage of these cells was also higher in high-grade tumors compared to low-grade ones (P = 0.031 for both). Our data collectively indicated that however approximately one third of CD4+ lymphocytes expressed CXCR5 and accordingly had the capacity to enter the follicles, less than 2% of them represented Tfh and TFR phenotypes. The percentage of these cells increased in progressed tumors and showed an association with negative prognostic factors.

Expansion of T follicular helper cells is associated with disease progression in rat experimental membranous nephropathy model.

BACKGROUND: T follicular helper (Tfh) cells drive humoral immunity by facilitating B cell responses, but the functional role of Tfh cells in the pathogenesis of idiopathic membranous nephropathy (IMN) remains unclear. OBJECTIVES: This study aimed to establish a rat experimental membranous nephropathy model, investigate the phenotypic characteristics of Tfh cells, and analyze a clinically significant correlation between Tfh cells. MATERIAL AND METHODS: Passive Heymann nephritis (PHN) rats were induced by immunizing Sprague Dawley rats with anti-Fx1A serum. The frequency of Tfh and B cell subsets was analyzed with flow cytometry (FC). The serum concentration of interleukin-21 (IL-21), the relative mRNA expression levels of IL-21 and B cell lymphoma 6 (Bcl-6) in spleen mononuclear cells (MNCs), and the kidney infiltration of CD4+ T cells and IL-21 were assessed. The potential correlations among these measures were analyzed. RESULTS: In comparison with the control group, significantly increased percentages of Tfh cells, inducible T cell co-stimulator-positive (ICOS+) Tfh cells, and mRNA expression of Bcl-6 were detected in the spleen of PHN rats. Elevated IL-21 expression was detected in the serum and kidneys. Remarkably, the percentage of splenic ICOS+ Tfh cells was positively correlated with 24 h urine protein concentrations (r = 0.676, p = 0.011) in PHN rats. CONCLUSION: These data indicate that ICOS+ Tfh cells contribute to development of IMN, and they might be potential therapeutic targets for IMN.

ATP-P2X7R pathway activation limits the Tfh cell compartment during pediatric RSV infection.

Background: Follicular helper T cells (Tfh) are pivotal in B cell responses. Activation of the purinergic receptor P2X7 on Tfh cells regulates their activity. We investigated the ATP-P2X7R axis in circulating Tfh (cTfh) cells during Respiratory Syncytial Virus (RSV) infection. Methods: We analyzed two cohorts: children with RSV infection (moderate, n=30; severe, n=21) and healthy children (n=23). We utilized ELISA to quantify the levels of PreF RSV protein-specific IgG antibodies, IL-21 cytokine, and soluble P2X7R (sP2X7R) in both plasma and nasopharyngeal aspirates (NPA). Additionally, luminometry was employed to determine ATP levels in plasma, NPA and supernatant culture. The frequency of cTfh cells, P2X7R expression, and plasmablasts were assessed by flow cytometry. To evaluate apoptosis, proliferation, and IL-21 production by cTfh cells, we cultured PBMCs in the presence of Bz-ATP and/or P2X7R antagonist (KN-62) and a flow cytometry analysis was performed. Results: In children with severe RSV disease, we observed diminished titers of neutralizing anti-PreF IgG antibodies. Additionally, severe infections, compared to moderate cases, were associated with fewer cTfh cells and reduced plasma levels of IL-21. Our investigation revealed dysregulation in the ATP-P2X7R pathway during RSV infection. This was characterized by elevated ATP levels in both plasma and NPA samples, increased expression of P2X7R on cTfh cells, lower levels of sP2X7R, and heightened ATP release from PBMCs upon stimulation, particularly evident in severe cases. Importantly, ATP exposure decreased cTfh proliferative response and IL-21 production, while promoting their apoptosis. The P2X7R antagonist KN-62 mitigated these effects. Furthermore, disease severity positively correlated with ATP levels in plasma and NPA samples and inversely correlated with cTfh frequency. Conclusion: Our findings indicate that activation of the ATP-P2X7R pathway during RSV infection may contribute to limiting the cTfh cell compartment by promoting cell death and dysfunction, ultimately leading to increased disease severity.

RACK1 enhances STAT3 stability and promotes T follicular helper cell development and function during blood-stage Plasmodium infection in mice.

CD4+ T cells are central mediators of protective immunity to blood-stage malaria, particularly for their capacity in orchestrating germinal center reaction and generating parasite-specific high-affinity antibodies. T follicular helper (Tfh) cells are predominant CD4+ effector T cell subset implicated in these processes, yet the factors and detailed mechanisms that assist Tfh cell development and function during Plasmodium infection are largely undefined. Here we provide evidence that receptor for activated C kinase 1 (RACK1), an adaptor protein of various intracellular signals, is not only important for CD4+ T cell expansion as previously implied but also plays a prominent role in Tfh cell differentiation and function during blood-stage Plasmodium yoelii 17XNL infection. Consequently, RACK1 in CD4+ T cells contributes significantly to germinal center formation, parasite-specific IgG production, and host resistance to the infection. Mechanistic exploration detects specific interaction of RACK1 with STAT3 in P. yoelii 17XNL-responsive CD4+ T cells, ablation of RACK1 leads to defective STAT3 phosphorylation, accompanied by substantially lower amount of STAT3 protein in CD4+ T cells, whereas retroviral overexpression of RACK1 or STAT3 in RACK1-deficient CD4+ T cells greatly restores STAT3 activity and Bcl-6 expression under the Tfh polarization condition. Further analyses suggest RACK1 positively regulates STAT3 stability by inhibiting the ubiquitin-proteasomal degradation process, thus promoting optimal STAT3 activity and Bcl-6 induction during Tfh cell differentiation. These findings uncover a novel mechanism by which RACK1 participates in posttranslational regulation of STAT3, Tfh cell differentiation, and subsequent development of anti-Plasmodium humoral immunity.

Dihydroartemisinin inhibits follicular helper T and B cells: implications for systemic lupus erythematosus treatment.

Systemic lupus erythematosus (SLE) is a common autoimmune disease, and its pathogenesis mainly involves the aberrant activation of B cells through follicular helper T (Tfh) cells to produce pathogenic antibodies, which requires more effective and safe treatment methods. Dihydroartemisinin (DHA) is the main active ingredient of artemisinin and has immunosuppressive effects. In this study, in vitro experiments confirmed that DHA inhibited Tfh cell induction and weakened its auxiliary function in B cell differentiation; furthermore, DHA directly inhibited B cell activation, differentiation, and antibody production. Furthermore, a mouse model of SLE was established, and we confirmed that DHA significantly reduced the symptoms of SLE and lupus nephritis, and decreased serum immunoglobulin (Ig)G, IgM, IgA, and anti-dsDNA levels. Moreover, DHA reduced the frequencies of total Tfh cells, activated Tfh cells, and B cell lymphoma 6, and interleukin (IL)-21 levels in Tfh cells from the spleen and lymph nodes, as well as the levels of B cells, germinal center B cells, and plasma cells in the spleen, lymph nodes, and kidneys. Additionally, DHA inhibited Tfh cells by blocking IL-2-inducible T cell kinase (ITK) signaling and its downstream nuclear factor (NF)-κB, nuclear factor of activated T cell, and activating protein-1 pathways, and directly inhibited B cells by blocking Bruton's tyrosine kinase (BTK) signaling and the downstream NF-κB and Myc pathways. Overall, our results demonstrated that DHA inhibited Tfh cells by blocking ITK signaling and also directly inhibited B cells by blocking BTK signaling. Therefore, reducing the production of pathogenic antibodies might effectively treat SLE.

ETV5 promotes lupus pathogenesis and follicular helper T cell differentiation by inducing osteopontin expression.

Follicular helper T (TFH) cells mediate germinal center reactions to generate high affinity antibodies against specific pathogens, and their excessive production is associated with the pathogenesis of systemic autoimmune diseases such as systemic lupus erythematosus (SLE). ETV5, a member of the ETS transcription factor family, promotes TFH cell differentiation in mice. In this study, we examined the role of ETV5 in the pathogenesis of lupus in mice and humans. T cell-specific deletion of Etv5 alleles ameliorated TFH cell differentiation and autoimmune phenotypes in lupus mouse models. Further, we identified SPP1 as an ETV5 target that promotes TFH cell differentiation in both mice and humans. Notably, extracellular osteopontin (OPN) encoded by SPP1 enhances TFH cell differentiation by activating the CD44-AKT signaling pathway. Furthermore, ETV5 and SPP1 levels were increased in CD4+ T cells from patients with SLE and were positively correlated with disease activity. Taken together, our findings demonstrate that ETV5 is a lupus-promoting transcription factor, and secreted OPN promotes TFH cell differentiation.

Modifying T cell phenotypes using TYK2 inhibitor and its implications for the treatment of systemic lupus erythematosus.

OBJECTIVES: The tuning effects of JAK/TYK2 inhibitors on the imbalance between T follicular helper (Tfh) and T regulatory (Treg) cells, related to systemic lupus erythematosus (SLE) pathogenesis, were investigated using human peripheral blood samples. METHODS: Peripheral blood mononuclear cells from untreated patients with SLE and healthy controls were analysed. Tfh1 cells were identified in nephritis tissue, and the effect of Tfh1 cells on B-cell differentiation was examined by coculturing naïve B cells with Tfh1 cells. RESULTS: Tfh1 cell numbers were increased in the peripheral blood of patients, and activated Treg cell counts were decreased relative to Tfh1 cell counts. This imbalance in the Tfh to Treg ratio was remarkably pronounced in cases of lupus nephritis, especially in types III and IV active nephritis. Immunohistochemistry revealed Tfh1 cell infiltration in lupus nephritis tissues. Co-culture of Tfh1 cells (isolated from healthy individuals) with naïve B cells elicited greater induction of T-bet+ B cells than controls. In JAK/TYK2-dependent STAT phosphorylation assays using memory CD4+ T cells, IL-12-induced STAT1/4 phosphorylation and Tfh1 cell differentiation were inhibited by both JAK and TYK2 inhibitors. However, phosphorylation of STAT5 by IL-2 and induction of Treg cell differentiation by IL-2+TGFß were inhibited by JAK inhibitors but not by TYK2 inhibitors, suggesting that TYK2 does not mediate the IL-2 signalling pathway. CONCLUSIONS: Tfh1 cells can induce T-bet+ B cell production and may contribute to SLE pathogenesis-associated processes. TYK2 inhibitor may fine-tune the immune imbalance by suppressing Tfh1 differentiation and maintaining Treg cell differentiation, thereby preserving IL-2 signalling, unlike other JAK inhibitors.

Transcriptional regulation of Tfh dynamics and the formation of immunological synapses.

Inside germinal centers (GCs), antigen-specific B cells rely on precise interactions with immune cells and strategic localization between the dark and light zones to clonally expand, undergo affinity maturation, and differentiate into long-lived plasma cells or memory B cells. Follicular helper T (Tfh) cells, the key gatekeepers of GC-dependent humoral immunity, exhibit remarkable dynamic positioning within secondary lymphoid tissues and rely on intercellular interactions with antigen-presenting cells (APCs) during their differentiation and execution of B-cell-facilitating functions within GCs. In this review, we briefly cover the transcriptional regulation of Tfh cell differentiation and function and explore the molecular mechanisms governing Tfh cell motility, their interactions with B cells within GCs, and the impact of their dynamic behavior on humoral responses.