The diagnostic role of PD-1+ CXCR5+ follicular helper CD8+ T cell in renal allograft dysfunction.

BACKGROUND: The roles of PD-1+ CXCR5+ follicular helper CD8+ T cell were reported in different disease conditions, but their roles in transplantation are unclear. In this study, the association between PD-1+ CXCR5+ follicular helper CD8+ T cell and renal allograft dysfunction in kidney transplant recipients (KTRs) was investigated. METHODS: 82 KTRs were enrolled in this study. 45 KTRs were included in the chronic allograft dysfunction (CAD) group, and 37 KTRs were included in the stable recipients group. Among the CAD group, 12 cases of antibody-mediated rejection (ABMR) and 4 cases of T cell-mediated rejection (TCMR) were diagnosed by biopsy. The percentage of CXCR5+ CD8+ T cells and the co-expression of signal transducers and activators of transcription 4 (STAT4), STAT5, and PD-1 in peripheral blood were determined by flow cytometry. RESULTS: The expression of CXCR5 on CD3+ CD8+ T cells and the percentage of STAT5+ CXCR5+ cells in the CD3+ CD8+ T-cell population were significantly lower in the CAD group (p < 0.05), while the expression of PD-1+ CXCR5+ CD8+ T cells was significantly higher (p < 0.05). Through logistic regression analysis, we concluded that the percentage of PD-1+ CXCR5+ CD8+ T cells was an independent risk factor for renal dysfunction. Grouping by pathological type, PD-1+ CXCR5+ CD8+ T cells showed relatively good diagnostic efficacy for ABMR by ROC analysis. CONCLUSIONS: Our results suggested that PD-1+ CXCR5+ CD8+ T cells were a promising biomarker for distinguishing renal allograft dysfunction and different allograft pathological types. Also, our findings may provide new ways of identifying and treating allograft rejection.

Follicular Helper CD4+ T Cells, Follicular Regulatory CD4+ T Cells, and Inducible Costimulator and Their Roles in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis.

Follicular helper CD4+ T (TFH) cells are a specialized subset of effector T cells that play a central role in orchestrating adaptive immunity. TFH cells mainly promote germinal center (GC) formation, provide help to B cells for immunoglobulin affinity maturation and class-switch recombination of B cells, and facilitate production of long-lived plasma cells and memory B cells. TFH cells express the nuclear transcriptional repressor B cell lymphoma 6 (Bcl-6), the chemokine (C-X-C motif) receptor 5 (CXCR5), the CD28 family members programmed cell death protein-1 (PD-1) and inducible costimulator (ICOS) and are also responsible for the secretion of interleukin-21 (IL-21) and IL-4. Follicular regulatory CD4+ T (TFR) cells, as a regulatory counterpart of TFH cells, participate in the regulation of GC reactions. TFR cells not only express markers of TFH cells but also express markers of regulatory T (Treg) cells containing FOXP3, glucocorticoid-induced tumor necrosis factor receptor (GITR), cytotoxic T lymphocyte antigen 4 (CTLA-4), and IL-10, hence owing to the dual characteristic of TFH cells and Treg cells. ICOS, expressed on activated CD4+ effector T cells, participates in T cell activation, differentiation, and effector process. The expression of ICOS is highest on TFH and TFR cells, indicating it as a key regulator of humoral immunity. Multiple sclerosis (MS) is a severe autoimmune disease that affects the central nervous system and results in disability, mediated by autoreactive T cells with evolving evidence of a remarkable contribution from humoral responses. This review summarizes recent advances regarding TFH cells, TFR cells, and ICOS, as well as their functional characteristics in relation to MS.

Selenium-GPX4 axis protects follicular helper T cells from ferroptosis.

Follicular helper T (TFH) cells are a specialized subset of CD4+ T cells that essentially support germinal center responses where high-affinity and long-lived humoral immunity is generated. The regulation of TFH cell survival remains unclear. Here we report that TFH cells show intensified lipid peroxidation and altered mitochondrial morphology, resembling the features of ferroptosis, a form of programmed cell death that is driven by iron-dependent accumulation of lipid peroxidation. Glutathione peroxidase 4 (GPX4) is the major lipid peroxidation scavenger and is necessary for TFH cell survival. The deletion of GPX4 in T cells selectively abrogated TFH cells and germinal center responses in immunized mice. Selenium supplementation enhanced GPX4 expression in T cells, increased TFH cell numbers and promoted antibody responses in immunized mice and young adults after influenza vaccination. Our findings reveal the central role of the selenium-GPX4-ferroptosis axis in regulating TFH homeostasis, which can be targeted to enhance TFH cell function in infection and following vaccination.

Erythropoietin Reduces Auto- and Alloantibodies by Inhibiting T Follicular Helper Cell Differentiation.

BACKGROUND: Although high-affinity IgG auto- and alloantibodies are important drivers of kidney inflammation that can result in ESKD, therapeutic approaches that effectively reduce such pathogenic antibodies remain elusive. Erythropoietin (EPO) has immunomodulatory functions, but its effects on antibody production are unknown. METHODS: We assessed the effect and underlying mechanisms of EPO/EPO receptor (EPOR) signaling on primary and secondary, T cell-dependent and T-independent antibody formation using in vitro culture systems, murine models of organ transplantation and lupus nephritis, and mice conditionally deficient for the EPOR expressed on T cells or B cells. RESULTS: In wild-type mice, recombinant EPO inhibited primary, T cell-dependent humoral immunity to model antigens and strong, polyclonal stimuli, but did not alter T-independent humoral immune responses. EPO also significantly impaired secondary humoral immunity in a potent allogeneic organ transplant model system. The effects required T cell, but not B cell, expression of the EPOR and resulted in diminished frequencies of germinal center (GC) B cells and T follicular helper cells (TFH). In vitro and in vivo experiments showed that EPO directly prevented TFH differentiation and function via a STAT5-dependent mechanism that reduces CD4+ T cell expression of Bcl6. In lupus models, EPO reduced TFH, GC B cells, and autoantibody production, and abrogated autoimmune glomerulonephritis, demonstrating clinical relevance. In vitro studies verified that EPO prevents differentiation of human TFH cells. CONCLUSIONS: Our findings newly demonstrate that EPO inhibits TFH-dependent antibody formation, an observation with potential implications for treating antibody-mediated diseases, including those of the kidney.

The kinase PDK1 is critical for promoting T follicular helper cell differentiation.

The kinase PDK1 is a crucial regulator for immune cell development by connecting PI3K to downstream AKT signaling. However, the roles of PDK1 in CD4+ T cell differentiation, especially in T follicular helper (Tfh) cell, remain obscure. Here we reported PDK1 intrinsically promotes the Tfh cell differentiation and germinal center responses upon acute infection by using conditional knockout mice. PDK1 deficiency in T cells caused severe defects in both early differentiation and late maintenance of Tfh cells. The expression of key Tfh regulators was remarkably downregulated in PDK1-deficient Tfh cells, including Tcf7, Bcl6, Icos, and Cxcr5. Mechanistically, ablation of PDK1 led to impaired phosphorylation of AKT and defective activation of mTORC1, resulting in substantially reduced expression of Hif1α and p-STAT3. Meanwhile, decreased p-AKT also suppresses mTORC2-associated GSK3ß activity in PDK1-deficient Tfh cells. These integrated effects contributed to the dramatical reduced expression of TCF1 and ultimately impaired the Tfh cell differentiation.

Galectin-9 regulates follicular helper T cells to inhibit humoral autoimmunity-induced pulmonary fibrosis.

Interstitial pneumonia with autoimmune features (IPAF) is an unexplained disease state characterized by autoimmunity and pulmonary fibrosis. Exploring the pathogenesis of IPAF is helpful for the treatment of interstitial pneumonia and idiopathic pulmonary fibrosis. In this study, we observed that the lung Galectin-9 (Gal-9) of IPAF patients was significantly reduced, which was significantly related to lung dysfunction and abnormal humoral immunity. Moreover, an overreactive germinal center (GC) reaction in the lung lymph nodes (LNs) of Gal-9-deficient mice was found to be related to abnormally active follicular helper T cells (Tfh) cells. The lack of Gal-9 ligand in Tfh cells can lead to excessive transcriptional programming and differentiation and help GC B cells. Gal-9 deficiency caused an abnormal humoral immune response in mice, leading to excessive deposition of nonspecific autoantibodies in mice and chronic lung fibrosis. Our research reveals the important regulatory role of gal-9 in Tfh cells and a possible target for the treatment of IPAF.

Coordinated Circulating T Follicular Helper and Activated B Cell Responses Underlie the Onset of Antibody-Mediated Rejection in Kidney Transplantation.

BACKGROUND: Although antibody-mediated rejection (ABMR) has been long recognized as a leading cause of allograft failure after kidney transplantation, the cellular and molecular processes underlying the induction of deleterious donor-specific antibody (DSA) responses remain poorly understood. METHODS: Using high-dimensional flow cytometry, in vitro assays, and RNA sequencing, we concomitantly investigated the role of T follicular helper (TFH) cells and B cells during ABMR in 105 kidney transplant recipients. RESULTS: There were 54 patients without DSAs; of those with DSAs, ABMR emerged in 20 patients, but not in 31 patients. We identified proliferating populations of circulating TFH cells and activated B cells emerging in blood of patients undergoing ABMR. Although these circulating TFH cells comprised heterogeneous phenotypes, they were dominated by activated (ICOS+PD-1+) and early memory precursor (CCR7+CD127+) subsets, and were enriched for the transcription factors IRF4 and c-Maf. These circulating TFH cells produced large amounts of IL-21 upon stimulation with donor antigen and induced B cells to differentiate into antibody-secreting cells that produced DSAs. Combined analysis of the matched circulating TFH cell and activated B cell RNA-sequencing profiles identified highly coordinated transcriptional programs in circulating TFH cells and B cells among patients with ABMR, which markedly differed from those of patients who did not develop DSAs or ABMR. The timing of expansion of the distinctive circulating TFH cells and activated B cells paralleled emergence of DSAs in blood, and their magnitude was predictive of IgG3 DSA generation, more severe allograft injury, and higher rate of allograft loss. CONCLUSIONS: Patients undergoing ABMR may benefit from monitoring and therapeutic targeting of TFH cell-B cell interactions.

Rejuvenating conventional dendritic cells and T follicular helper cell formation after vaccination.

Germinal centres (GCs) are T follicular helper cell (Tfh)-dependent structures that form in response to vaccination, producing long-lived antibody secreting plasma cells and memory B cells that protect against subsequent infection. With advancing age the GC and Tfh cell response declines, resulting in impaired humoral immunity. We sought to discover what underpins the poor Tfh cell response in ageing and whether it is possible to correct it. Here, we demonstrate that older people and aged mice have impaired Tfh cell differentiation upon vaccination. This deficit is preceded by poor activation of conventional dendritic cells type 2 (cDC2) due to reduced type 1 interferon signalling. Importantly, the Tfh and cDC2 cell response can be boosted in aged mice by treatment with a TLR7 agonist. This demonstrates that age-associated defects in the cDC2 and Tfh cell response are not irreversible and can be enhanced to improve vaccine responses in older individuals.

Primary T-Cell Transduction to Study Follicular Helper T-Cell Differentiation.

Follicular helper T (Tfh) cells constitute a specialized CD4+ T-cell subset that localizes in close proximity to B cells and are essential in the production of high-affinity, class-switched antibodies, and their dysregulations are also involved in autoimmune diseases. Modulating gene expression patterns in primary T cells is an important approach to understanding Tfh cell differentiation and function. In this chapter, we describe a protocol to evaluate Tfh cell differentiation with OT-II TCR transgenic T cells by retrovirally transducing gene of interest. This protocol adopts the recombinant retrovirus-based transduction of primary CD4+ T cells, and it also includes procedures for adoptive transfer, immunization, and flow cytometry analysis.

Acetylcholine regulates the development of experimental autoimmune encephalomyelitis via the CD4+ cells proliferation and differentiation.

Purpose of the study: Multiple sclerosis is a CD4+ T cell mediated autoimmune disease characterized by inflammatory demyelination in the central nervous system. Acetylcholine (ACh) has been reported to be released by T lymphocytes and plays as an inflammation and immune regulator through the participation of T cells. However, both attenuated and aggravated effects of ACh in inflammation were found. The aim of this study is to further investigate the role of ACh in experimental autoimmune encephalomyelitis (EAE).Materials and methods: The left cervical vagotomy was performed to inhibit ACh release with the sham-operation as control. ACh in cerebral cortex and splenocytes culture supernatants of EAE mice were determined. Interleukin-6, interferon-γ, interleukin-4 and interleukin-17A in brain and splenocytes culture supernatants were evaluated by enzyme-linked immunosorbent assay. The proportion of CD4+ T cells and subsets were assessed by flow cytometry.Results: Compared with the sham-operation group, improved clinical and pathological parameters as well as decreased interleukin-6, interferon-γ, interleukin-4 and interleukin-17A were found in EAE mice with vagotomy suppressing the ACh. Marked reductions of CD4+ and CD4+ChAT+ cells, as well as significant decrease in Th1 with a bias to Th2 in Th1/Th2 balance and increased ChAT+Th2 proportion in the spleen were also observed in vagotomized mice.Conclusions: These findings emphasize that inhibiting ACh release by vagotomy can ameliorate the exacerbation of EAE through suppressing CD4+ T cells proliferation and regulating the differentiation of Th1, Th2 and Th17.

BCL6 BTB-specific inhibition via FX1 treatment reduces Tfh cells and reverses lymphoid follicle hyperplasia in Indian rhesus macaque (Macaca mulatta).

BACKGROUND: The BTB domain of B-cell lymphoma 6 (BCL6) protein was identified as a therapeutic target for B-cell lymphoma. This study compared the pharmacokinetics (PK) of the BCL6 BTB inhibitor (FX1) between mice and macaques, as well as evaluating its lymphoid suppressive effect in uninfected macaques with lymphoid hyperplasia. MATERIALS AND METHODS: Eight uninfected adult Indian rhesus macaques (Macaca mulatta) were used in the study, four animals carrying lymphoid tissue hyperplasia. Plasma FX1 levels were measured by HPLC-MS/MS. Lymph node biopsies were used for H&E and immunohistochemistry staining, as well as mononuclear cell isolation for flow cytometry analysis. RESULTS: Inhibition of the BCL6 BTB domain with FX1 led to a reduction in the frequency of GC, Tfh CD4+ , and Tfh precursor cells, as well as resolving lymphoid hyperplasia, in rhesus macaques. CONCLUSIONS: B-cell lymphoma 6 inhibition may represent a novel strategy to reduce hyperplastic lymphoid B-cell follicles and decrease Tfh cells.