Phenotype and functions of memory Tfh cells in human blood

T follicular helper cell profiles differ by malaria antigen and for children compared to adults

Background

Circulating T-follicular helper (cT FH ) cells have the potential to provide an additional correlate of protection against Plasmodium falciparum ( Pf) as they are essential to promote B cell production of long-lasting antibodies. Assessing the specificity of cT FH subsets to individual malaria antigens is vital to understanding the variation observed in antibody responses and identifying promising malaria vaccine candidates.

Methods

Using spectral flow cytometry and unbiased clustering analysis we assessed antigen-specific cT FH cell recall responses in vitro to malaria vaccine candidates Pf SEA-1A and Pf GARP within a cross-section of children and adults living in a malaria holoendemic region of western Kenya.

Findings

In children, a broad array of cT FH subsets (defined by cytokine and transcription factor expression) were reactive to both malaria antigens, Pf SEA-1A and Pf GARP, while adults had a narrow profile centering on cT FH 17- and cT FH 1/17-like subsets following stimulation with Pf GARP only.

Interpretation

Because T FH 17 cells are involved in the maintenance of memory antibody responses within the context of parasitic infections, our results suggest that Pf GARP might generate longer lived antibody responses compared to Pf SEA-1A. These findings have intriguing implications for evaluating malaria vaccine candidates as they highlight the importance of including cT FH profiles when assessing interdependent correlates of protective immunity.

Vaccines Induce Homeostatic Immunity, Generating Several Secondary Benefits

The optimal immune response eliminates invading pathogens, restoring immune equilibrium without inflicting undue harm to the host. However, when a cascade of immunological reactions is triggered, the immune response can sometimes go into overdrive, potentially leading to harmful long-term effects or even death. The immune system is triggered mostly by infections, allergens, or medical interventions such as vaccination. This review examines how these immune triggers differ and why certain infections may dysregulate immune homeostasis, leading to inflammatory or allergic pathology and exacerbation of pre-existing conditions. However, many vaccines generate an optimal immune response and protect against the consequences of pathogen-induced immunological aggressiveness, and from a small number of unrelated pathogens and autoimmune diseases. Here, we propose an "immuno-wave" model describing a vaccine-induced "Goldilocks immunity", which leaves fine imprints of both pro-inflammatory and anti-inflammatory milieus, derived from both the innate and the adaptive arms of the immune system, in the body. The resulting balanced, 'quiet alert' state of the immune system may provide a jump-start in the defense against pathogens and any associated pathological inflammatory or allergic responses, allowing vaccines to go above and beyond their call of duty. In closing, we recommend formally investigating and reaping many of the secondary benefits of vaccines with appropriate clinical studies.

Circulating Immune Landscape Profiling in Psoriasis Vulgaris and Psoriatic Arthritis by Mass Cytometry

Background

Psoriasis, a systemic disorder mediated by the immune system, can appear on the skin, joints, or both. Individuals with cutaneous psoriasis (PsC) have an elevated risk of developing psoriatic arthritis (PsA) during their lifetime. Despite this known association, the cellular and molecular mechanisms underlying this progression remain unclear.

Methods

We performed high-dimensional, in-depth immunophenotyping of peripheral blood mononuclear cells (PBMCs) in patients with PsA and psoriasis vulgaris (PsV) by mass cytometry. Blood samples were collected before and after therapy for a longitudinal study. Then three sets of comparisons were made here: active PsA vs. active PsV, untreated PsV vs. treated PsV, and untreated PsA vs. treated PsA.

Results

Marked differences were observed in multiple lymphocyte subsets of PsA related to PsV, with expansion of CD4+ T cells, CD16- NK cells, and B cells. Notably, two critical markers, CD28 and CD127, specifically differentiated PsA from PsV. The expression levels of CD28 and CD127 on both Naïve T cells (TN) and central memory CD4+ T cells (TCM) were considerably higher in PsA than PsV. Meanwhile, after treatment, patients with PsV had higher levels of CD28hi CD127hi CD4+ TCM cells, CD28hi CD127hi CD4+ TN cells, and CD16- NK cells.

Conclusion

In the circulation of PsA patients, the TN and CD4+ TCM are characterized with more abundant CD28 and CD127, which effectively distinguished PsA from PsV. This may indicate that individuals undergoing PsV could be stratified at high risk of developing PsA based on the circulating levels of CD28 and CD127 on specific cell subsets.

Clinicopathological implications of immunohistochemical expression of TBX21, CXCR3, GATA3, CCR4, and TCF1 in nodal follicular helper T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified

BACKGROUND

The classification of nodal peripheral T-cell lymphoma (PTCL) has evolved according to histology, cell-of-origin, and genetic alterations. However, the comprehensive expression pattern of follicular helper T-cell (Tfh) markers, T-cell factor-1 (TCF1), and Th1- and Th2-like molecules in nodal PTCL is unclear.

METHODS

Eighty-two cases of nodal PTCL were classified into 53 angioimmunoblastic T-cell lymphomas (AITLs)/nodal T-follicular helper cell lymphoma (nTFHL)-AI, 18 PTCLs-Tfh/nTFHL-not otherwise specified (NOS), and 11 PTCLs-NOS according to the revised 4th/5th World Health Organization classifications. Immunohistochemistry for TCF1, TBX21, CXCR3, GATA3, and CCR4 was performed.

RESULTS

TCF1 was highly expressed in up to 68% of patients with nTFHL but also in 44% of patients with PTCL-NOS (p > .05). CXCR3 expression was higher in AITLs than in non-AITLs (p = .035), whereas GATA3 expression was higher in non-AITL than in AITL (p = .007) and in PTCL-Tfh compared to AITL (p = .010). Of the cases, 70% of AITL, 44% of PTCLTfh/ nTFHL-NOS, and 36% of PTCL-NOS were subclassified as the TBX21 subtype; and 15% of AITL, 38% of PTCL-Tfh/nTFHL-NOS, and 36% of PTCL-NOS were subclassified as the GATA3 subtype. The others were an unclassified subtype. CCR4 expression was associated with poor progression-free survival (PFS) in patients with PTCL-Tfh (p < .001) and nTFHL (p = .023). The GATA3 subtype showed poor overall survival in PTCL-NOS compared to TBX21 (p = .046) and tended to be associated with poor PFS in patients with non-AITL (p = .054).

CONCLUSIONS

The TBX21 subtype was more prevalent than the GATA3 subtype in AITL. The GATA3 subtype was associated with poor prognosis in patients with non-AITL and PTCL-NOS.

Helios characterized circulating follicular helper T cells with enhanced functional phenotypes and was increased in patients with systemic lupus erythematosus

Helios was related to the immunosuppressive capacity and stability of regulatory T cells. However, the significance of Helios in follicular help T (TFH) and follicular regulatory T (TFR) cells is unclear. This research aimed to clarify the significance of Helios (IKZF2) in TFH and TFR cells and its clinical value in systemic lupus erythematosus (SLE). IKZF2 mRNA in different cell subsets was analyzed. Helios+ percentages in TFH and TFR cells were identified in the peripheral blood of 75 SLE patients and 62 HCs (healthy controls). PD-1 and ICOS expression were compared between Helios+ and Helios- cells. The capacity of TFH cells to secrete IL-21 and TFR cells to secrete IL-10 was measured. Correlation analysis and receiver operating characteristic (ROC) curve analysis were conducted to assess the clinical significance of Helios-related TFH and TFR cell subsets in SLE. There was Helios expression in TFH and TFR cells. PD-1 and ICOS were lower in Helios+ TFR than in Helios- TFR. ICOS was increased in Helios+ TFH cells compared with Helios- TFH cells, and ICOS in Helios+ TFH cells was downregulated in SLE. Helios+ TFH cells secreted more IL-21 than Helios- TFH cells, and Helios+ TFH cells from SLE patients had a stronger IL-21 secretion than HCs. Helios+ TFH percentages were negatively correlated with C3 and C4 and positively related to CRP and SLEDAI, and the AUC of Helios+ TFH to distinguish SLE from HC was 0.7959. Helios characterizes circulating TFH cells with enhanced function. Increased Helios+ TFH cells could reflect the autoimmune status of SLE.

Sarcoidosis-related autoimmune inflammation in COVID-19 convalescent patients

Currently, there are a large number of reports about the development of autoimmune conditions after COVID-19. Also, there have been cases of sarcoid-like granulomas in convalescents as a part of the post-COVID-19 syndrome. Since one of the etiological theories of sarcoidosis considers it to be an autoimmune disease, we decided to study changes in the adaptive humoral immune response in sarcoidosis and SARS-CoV-2 infection and to find out whether COVID-19 can provoke the development of sarcoidosis. This review discusses histological changes in lymphoid organs in sarcoidosis and COVID-19, changes in B cell subpopulations, T-follicular helper cells (Tfh), and T-follicular regulatory cells (Tfr), and analyzes various autoantibodies detected in these pathologies. Based on the data studied, we concluded that SARS-CoV-2 infection may cause the development of autoimmune pathologies, in particular contributing to the onset of sarcoidosis in convalescents.

Alterations in Helios+ T cell subsets in peripheral blood of early-stage lung adenocarcinoma patients: Implications for early diagnosis

OBJECTIVE

This study aimed to investigate the changes and significance of circulating Helios-associated T cell subsets in patients with early-stage lung adenocarcinoma (LUAD).

METHODS

Blood samples were collected from 35 healthy controls and 34 patients with early-stage LUAD. Flow cytometry was used to analyze various CD4+ T cell subsets, including regulatory T(Treg) cells, follicular regulatory T(Tfr) cells, follicular helper T (Tfh) cells, and conventional T (con-T) cells. Correlation analysis was conducted to investigate the association of Helios-related subsets with clinical indicators. The ROC curve was used to explore the potential clinical value of Helios+ T cell subsets in the screening of patients with early LUAD. Fifteen of these patients were tracked after lung cancer resection and changes in Helios+ T cell subsets before and after treatment were analyzed.

RESULTS

The percentage and absolute number of Tregs were up-regulated in LUAD patients while Tfh and con-T cells expressing Helios were down-regulated. Absolute counts of Tfr and con-T cells and Helios expression in Tfr and Treg decreased significantly after resection. Helios+ Tfh and con-T were negatively correlated with certain tumor markers. Areas under the curve (AUCs) of percentages and absolute counts of Helios+ Tfh, Treg, Tfr and con-T cells to distinguish early LUAD from healthy individuals were 0.7277, 0.5697, 0.5718, 0.7210 (percentages), 0.7336, 0.7378, 0.5908 and 0.7445(absolute numbers), respectively.

CONCLUSION

Helios+ T cell subsets in peripheral blood of early-stage LUAD patients has changed significantly, which may be related to the pathogenesis of LUAD and could help for early diagnosis of LUAD.

Leptin favors imbalance of antigen-specific CD4+ T-cells associated with severity of cat allergy

Introduction

Obesity can complicate IgE-mediated allergic diseases. In the present study, we aimed to investigate the ability of obesity-related concentrations of leptin to modulate the in vitro effector and regulatory Fel d1-specific CD4+ T-cell subsets in patients allergic to cat, considered the third most common cause of respiratory allergy in humans.

Methods

For this study, plasma and peripheral blood mononuclear cells (PBMC) from 30 cat-allergic patients with mild, moderate and severe respiratory symptoms were obtained. The PBMC cultures were stimulated with Fel d1 antigen (10 µg/mL) in the presence or absence of obesity-related leptin dose (50 ηg/mL). After 6 days, the levels of cytokines and IgE in the supernatants were evaluated by multiplex and ELISA, respectively. The frequency of different non-follicular (CXCR5-) and follicular (CXCR5+) Fel d1-specific CD4+ T cell subsets was determined by flow cytometry. The plasma levels of leptin and IgE anti-cat titers were evaluated by ELISA and ImmunoCAP, respectively.

Results and conclusions

Fel d1 induced both IgE production and release of cytokines related to Th2, Th9 and Th17 cell phenotypes. Feld1 was more efficient in increasing the frequency of TFHIL-21- cells positive for IL-4, IL-5 and IL-13 than TFHIL-21+ cell subsets. Leptin favored the expansion Th2-like and Th9-like cells and TFHIL-21- cells positive for IL-4, IL-5 and IL-13, but reduced the proportion of conventional (Treg/Tr-1) and follicular (TFR) regulatory CD4+ T-cell subsets expressing or not CD39 marker. Finally, many of the imbalances between Fel d1-specific CD4+ T-cells were also correlated with plasma leptin and anti-Fel d1 IgE titers. In summary, hyperleptinemia should negatively impact on the severity of cat allergies by favoring the expansion of pathogenic Fel d1-specific CD4+ T-cell phenotypes and damaging the functional status of regulatory CD4+ T-cell subsets.

The roles of T cells in psoriasis

Psoriasis is a recurring inflammatory skin condition characterized by scaly, red patches on the skin. It affects approximately 3% of the US population and is associated with histological changes such as epidermal hyperplasia, increased blood vessel proliferation, and infiltration of leukocytes into the skin's dermis. T cells, which are classified into various subtypes, have been found to play significant roles in immune-mediated diseases, particularly psoriasis. This paper provides a review of the different T lymphocyte subtypes and their functions in psoriasis, as well as an overview of targeted therapies for treating psoriasis.

Rituximab induces a transient fluctuation of peripheral and follicular helper T cells in neuromyelitis optica spectrum disorder

Autoreactive CD4+ helper T cells are implicated in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD). Both PD-1+CXCR5+CD4+ T follicular helper (Tfh) cells and PD-1+CXCR5-CD4+ T peripheral helper (Tph) cells can contribute to B-cell immune responses and the production of antibodies. Here we show the effect of B-cell depletion with rituximab on the homeostasis of Tfh cells, Tph cells and their subsets in patients with NMOSD. After rituximab treatment, total Tph cells, total Tfh cells, Tph17 cells, Tph17.1 cells, Tph1 cells, and Tfh1 cells tended to decrease at month 1, but gradually increased at month 6 and restored at month 12. Besides, Tph17.1 cells and Tfh17.1 cells were correlated with the proportion of CD19- antibody-secreting cells. Our data suggest that rituximab induced a fluctuation of proinflammatory Tph and Tfh subsets within one year after initiation of the treatment.

Perturbations in spike-specific peripheral T follicular helper cells in SARS-CoV2 breakthrough convalescent individuals immunized by BBV152 vaccine

Severe acute respiratory syndrome coronavirus 2 (SARS-Cov2) infection has caused an increase in mortality and morbidity, but with vaccination, the disease severity has significantly reduced. With the emergence of various variants of concern (VOCs), the vaccine breakthrough infection has also increased. Here we studied circulating spike-specific T follicular response (cTfh) in infection-naïve vaccinees and convalescent vaccinees (individuals who got the Delta breakthrough infection after two doses of BBV152 vaccine) to understand their response as they are the most crucial cells that are involved in vaccine-mediated protection by helping in B-cell maturation. Our results indicated that cTfh cells in both the groups recognized the wild-type and Delta spike protein but memory response to the wild-type spike was superior in infection-naïve than in the convalescent group. The cytokine response, particularly interleukin-21 (IL-21) from cTfh, was also higher in infection-naïve than in convalescent vaccinees, indicating a dampened cTfh response in convalescent vaccinees after breakthrough infection. Also, there was a positive correlation between IL-21 from cTfh cells and neutralizing antibodies of infection-naïve vaccinees. Multiple cytokine analysis also revealed higher inflammation in convalescent vaccinees. Our data indicated that the necessity of a third booster dose may be individual-specific depending on the steady-state functional phenotype of immune cells.

T Follicular Helper Cells in Tertiary Lymphoid Structure Contribute to Renal Fibrosis by IL-21

Tertiary lymphoid structure (TLS) represents lymphocyte clusters in non-lymphoid organs. The formation and maintenance of TLS are dependent on follicular helper T (TFH) cells. However, the role of TFH cells during renal TLS formation and the renal fibrotic process has not been comprehensively elucidated in chronic kidney disease. Here, we detected the circulating TFH cells from 57 IgAN patients and found that the frequency of TFH cells was increased in IgA nephropathy patients with renal TLS and also increased in renal tissues from the ischemic-reperfusion-injury (IRI)-induced TLS model. The inducible T-cell co-stimulator (ICOS) is one of the surface marker molecules of TFH. Remarkably, the application of an ICOS-neutralizing antibody effectively prevented the upregulation of TFH cells and expression of its canonical functional mediator IL-21, and also reduced renal TLS formation and renal fibrosis in IRI mice in vivo. In the study of this mechanism, we found that recombinant IL-21 could directly promote renal fibrosis and the expression of p65. Furthermore, BAY 11-7085, a p65 selective inhibitor, could effectively alleviate the profibrotic effect induced by IL-21 stimulation. Our results together suggested that TFH cells contribute to TLS formation and renal fibrosis by IL-21. Targeting the ICOS-signaling pathway network could reduce TFH cell infiltration and alleviate renal fibrosis.

Immune surveillance and humoral immune responses in kidney transplantation - A look back at T follicular helper cells

T follicular helper cells comprise a specialized, heterogeneous subset of immune-competent T helper cells capable of influencing B cell responses in lymphoid tissues. In physiology, for example in response to microbial challenges or vaccination, this interaction chiefly results in the production of protecting antibodies and humoral memory. In the context of kidney transplantation, however, immune surveillance provided by T follicular helper cells can take a life of its own despite matching of human leukocyte antigens and employing the latest immunosuppressive regiments. This puts kidney transplant recipients at risk of subclinical and clinical rejection episodes with a potential risk for allograft loss. In this review, the current understanding of immune surveillance provided by T follicular helper cells is briefly described in physiological responses to contrast those pathological responses observed after kidney transplantation. Sensitization of T follicular helper cells with the subsequent emergence of detectable donor-specific human leukocyte antigen antibodies, non-human leukocyte antigen antibodies their implication for kidney transplantation and lessons learnt from other transplantation "settings" with special attention to antibody-mediated rejection will be addressed.

Circulating Th2-biased T follicular helper cells impede antiviral humoral responses during chronic hepatitis B infection through upregulating CTLA4

Failure in curing chronic hepatitis B (CHB) caused by hepatitis B virus (HBV) can lead to functional impairment of B cells. Cytotoxic T-lymphocyte associated antigen 4 (CTLA4) regulates B cell and T follicular helper (Tfh) cell differentiation. In addition, Tfh cells play a critical role in helping B cells generate antibodies upon pathogen exposure. Here, we analyzed the global and HBsAg-specific B cells and circulating Tfh (cTfh) cells using samples from treatment-naïve and Peg-IFN-α-treated CHB patients and healthy subjects. Compared to healthy subjects, CTLA4 expression was significantly increased in cTfh cells, from CHB patients. The frequency of CTLA4⁺cTfh2 cells was negatively correlated with that of HBsAg-specific resting memory B cells. Importantly, inhibition of CTLA4 restored HBsAb secretion and promoted plasma cell differentiation. In addition, CTLA4⁺cTfh2 cells from CHB patients were ineffective in providing B cell help. Both expression of CTLA4 in cTfh and cTfh2 cells and ratios of CLTA4⁺cTfh and CTLA4⁺cTfh2 cells were significantly decreased in Peg-IFN-α-treated CHB patients who showed complete responses. Thus, our results highlighted that cTh2-biased T follicular helper cells could impede antiviral humoral responses during chronic HBV infection by upregulating CTLA4, suggesting that further optimizing potent Tfh cell responses may promote functional cure of CHB.

Clinical manifestations and immune response to tuberculosis

Tuberculosis is a far-reaching, high-impact disease. It is among the top ten causes of death worldwide caused by a single infectious agent; 1.6 million tuberculosis-related deaths were reported in 2021 and it has been estimated that a third of the world's population are carriers of the tuberculosis bacillus but do not develop active disease. Several authors have attributed this to hosts' differential immune response in which cellular and humoral components are involved, along with cytokines and chemokines. Ascertaining the relationship between TB development's clinical manifestations and an immune response should increase understanding of tuberculosis pathophysiological and immunological mechanisms and correlating such material with protection against Mycobacterium tuberculosis. Tuberculosis continues to be a major public health problem globally. Mortality rates have not decreased significantly; rather, they are increasing. This review has thus been aimed at deepening knowledge regarding tuberculosis by examining published material related to an immune response against Mycobacterium tuberculosis, mycobacterial evasion mechanisms regarding such response and the relationship between pulmonary and extrapulmonary clinical manifestations induced by this bacterium which are related to inflammation associated with tuberculosis dissemination through different routes.

Characterization of peripheral blood T follicular helper (TFH) cells in patients with type 1 Gaucher disease and carriers

BACKGROUND

Gaucher disease (GD) is the most common autosomal recessive lipid storage disease. In this study, the changes in TFH cells and IL-4 and IL-21 cytokines in blood samples of GD patients, carriers and healthy volunteers were investigated.

METHODS

Two pretreatment type 1 GD patients, 20 currently treated type 1 GD patients, 6 carriers, and 27 healthy volunteers were enrolled in the study. TFH cell (CD45RA^-CD4⁺CXCR5⁺) number, phenotype (PD1, ICOS expression), and cytokine production (IL-21, IL-4) were assessed via flow cytometric assays.

RESULTS

No significant differences were found between the groups with respect to the number, frequency and PD1 or ICOS expression of TFH cells between healthy controls, patients and carriers. However, IL-4⁺ TFH cells were significantly reduced both in percent and number in the treated GD patients compared with healthy controls (p < 0.05). Interestingly, the IL-21⁺ TFH cell number was increased in treated GD patients. When TFH cells were examined based on CXCR3 expression, the frequency of the PD1⁺Th17-Th2-like fraction (CXCR3^-) was found to be significantly increased in treated GD patients.

CONCLUSION

To our knowledge, this is the first study to assess TFH cells in GD patients, and to show that the production of IL-4 and IL-21 by TFH cells and their subsets may be altered in type 1 GD patients.

Delayed generation of functional virus-specific circulating T follicular helper cells correlates with severe COVID-19

Effective humoral immune responses require well-orchestrated B and T follicular helper (Tfh) cell interactions. Whether these interactions are impaired and associated with COVID-19 disease severity is unclear. Here, longitudinal blood samples across COVID-19 disease severity are analysed. We find that during acute infection SARS-CoV-2-specific circulating Tfh (cTfh) cells expand with disease severity. SARS-CoV-2-specific cTfh cell frequencies correlate with plasmablast frequencies and SARS-CoV-2 antibody titers, avidity and neutralization. Furthermore, cTfh cells but not other memory CD4 T cells, from severe patients better induce plasmablast differentiation and antibody production compared to cTfh cells from mild patients. However, virus-specific cTfh cell development is delayed in patients that display or later develop severe disease compared to those with mild disease, which correlates with delayed induction of high-avidity neutralizing antibodies. Our study suggests that impaired generation of functional virus-specific cTfh cells delays high-quality antibody production at an early stage, potentially enabling progression to severe disease.

Characterizing the Interplay of Lymphocytes in Graves' Disease

Graves' disease (GD) is a thyroid-specific autoimmune disease with a high prevalence worldwide. The disease is primarily mediated by B cells, which produce autoantibodies against the thyroid-stimulating hormone receptor (TSHR), chronically stimulating it and leading to high levels of thyroid hormones in the body. Interest in characterizing the immune response in GD has motivated many phenotyping studies. The immunophenotype of the cells involved and the interplay between them and their secreted factors are crucial to understanding disease progression and future treatment options. T cell populations are markedly distinct, including increased levels of Th17 and follicular helper T cells (Tfh), while Treg cells appear to be impaired. Some B cells subsets are autoreactive, and anti-TSHR antibodies are the key disease-causing outcome of this interplay. Though some consensus across phenotyping studies will be discussed here, there are also complexities that are yet to be resolved. A better understanding of the immunophenotype of Graves' disease can lead to improved treatment strategies and novel drug targets.

Dysregulation of circulating CD4 + CXCR5 + PD-1+ T cells in diabetic retinopathy

AIMS

We aimed to determine an association between follicular helper T (Tfh) cells and Bcl-6 and CXCL13 levels and determine the role of Tfh cells, Bcl-6, and CXCL13 serum levels in the pathogenesis of diabetic retinopathy (DR) since Tfh cells have an important role in type 1 diabetes; however, their role in type 2 diabetes-related DR requires exploration.

METHODS

Blood samples were collected from 24 patients with non-proliferative diabetic retinopathy (NPDR), 20 with proliferative diabetic retinopathy (PDR), and 18 age- and sex-matched healthy volunteers. Flow cytometry detected CD4 + CXCR5 + PD1+ Tfh cells. Serum Bcl-6 and CXCL13 levels were determined using enzyme-linked immunosorbent assay.

RESULTS

CD4 + CXCR5 + PD-1+ Tfh cell percentages in peripheral blood and serum levels of Bcl-6 and CXCL13 in the non-proliferative DR (NPDR) and proliferative DR (PDR) groups' were significantly higher than those in healthy individuals. The proportion of Tfh cells in DR patients' peripheral blood positively correlated with Bcl-6 and CXCL13 serum levels, DR course severity, Fasting blood glucose, glycosylated hemoglobin and body mass index.

CONCLUSIONS

The increased circulating Tfh cells, serum Bcl-6 levels, and CXCL13 levels of DR patients with type 2 diabetes suggested that circulating Tfh cells and the germinal center response may have a role in the occurrence and development of DR.

COVID-19 Vaccination Responses with Different Vaccine Platforms in Patients with Inborn Errors of Immunity

Patients with inborn errors of immunity (IEI) in Argentina were encouraged to receive licensed Sputnik, AstraZeneca, Sinopharm, Moderna, and Pfizer vaccines, even though most of the data of humoral and cellular responses combination on available vaccines comes from trials conducted in healthy individuals. We aimed to evaluate the safety and immunogenicity of the different vaccines in IEI patients in Argentina. The study cohort included adults and pediatric IEI patients (n = 118) and age-matched healthy controls (HC) (n = 37). B cell response was evaluated by measuring IgG anti-spike/receptor binding domain (S/RBD) and anti-nucleocapsid(N) antibodies by ELISA. Neutralization antibodies were also assessed with an alpha-S protein-expressing pseudo-virus assay. The T cell response was analyzed by IFN-γ secretion on S- or N-stimulated PBMC by ELISPOT and the frequency of S-specific circulating T follicular-helper cells (TFH) was evaluated by flow cytometry.No moderate/severe vaccine-associated adverse events were observed. Anti-S/RBD titers showed significant differences in both pediatric and adult IEI patients versus the age-matched HC cohort (p < 0.05). Neutralizing antibodies were also significantly lower in the patient cohort than in age-matched HC (p < 0.01). Positive S-specific IFN-γ response was observed in 84.5% of IEI patients and 82.1% presented S-specific TFH cells. Moderna vaccines, which were mainly administered in the pediatric population, elicited a stronger humoral response in IEI patients, both in antibody titer and neutralization capacity, but the cellular immune response was similar between vaccine platforms. No difference in humoral response was observed between vaccinated patients with and without previous SARS-CoV-2 infection.In conclusion, COVID-19 vaccines showed safety in IEI patients and, although immunogenicity was lower than HC, they showed specific anti-S/RBD IgG, neutralizing antibody titers, and T cell-dependent cellular immunity with IFN-γ secreting cells. These findings may guide the recommendation for a vaccination with all the available vaccines in IEI patients to prevent COVID-19 disease.

T follicular helper cells and T follicular regulatory cells in autoimmune diseases

T follicular helper (Tfh) cells are heterogeneous and mainly characterized by expressing surface markers CXCR5, ICOS, and PD-1; cytokine IL-21; and transcription factor Bcl6. They are crucial for B-cell differentiation into long-lived plasma cells and high-affinity antibody production. T follicular regulatory (Tfr) cells were described to express markers of conventional T regulatory (Treg) cells and Tfh cells and were able to suppress Tfh-cell and B-cell responses. Evidence has revealed that the dysregulation of Tfh and Tfr cells is positively associated with the pathogenic processes of autoimmune diseases. Herein, we briefly introduce the phenotype, differentiation, and function of Tfh and Tfr cells, and review their potential roles in autoimmune diseases. In addition, we discuss perspectives to develop novel therapies targeting Tfh/Tfr balance.

T follicular helper cells in autoimmune diseases

T follicular helper (Tfh) cells with the phenotype of mainly expressing surface molecules C-X-C motif chemokine receptor type 5 (CXCR5), inducible co-stimulator (ICOS), secreting cytokine interleukin-21 (IL-21) and requiring the transcription factor B cell lymphoma 6 (BCL-6) have been recently defined as a new subset of CD4⁺ T cells. They exist in germinal centers (GCs) of lymphoid organs and in peripheral blood. With the ability to promote B cell development, GC formation and antibody production, Tfh cells play critical roles in the pathogenesis of many autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), primary Sjögren's syndrome (pSS), etc. The aberrant proliferation and function of Tfh cells will cause the pathological process like autoantibody production and tissue injury. In this paper, we review the recent advances in Tfh cell biology and their roles in autoimmune diseases, with a mention of their use as therapeutic targets, which will shed more light on the pathogenesis and treatment of certain autoimmune diseases.

Characterization of post-vaccination SARS-CoV-2 T cell subtypes in patients with different hematologic malignancies and treatments

Background

To evaluate the benefits of SARS-CoV-2 vaccination in cancer patients it is relevant to understand the adaptive immune response elicited after vaccination. Patients affected by hematologic malignancies are frequently immune-compromised and show a decreased seroconversion rate compared to other cancer patients or controls. Therefore, vaccine-induced cellular immune responses in these patients might have an important protective role and need a detailed evaluation.

Methods

Certain T cell subtypes (CD4, CD8, Tfh, γδT), including cell functionality as indicated by cytokine secretion (IFN, TNF) and expression of activation markers (CD69, CD154) were assessed via multi-parameter flow cytometry in hematologic malignancy patients (N=12) and healthy controls (N=12) after a second SARS-CoV-2 vaccine dose. The PBMC of post-vaccination samples were stimulated with a spike-peptide pool (S-Peptides) of SARS-CoV-2, with CD3/CD28, with a pool of peptides from the cytomegalovirus, Epstein-Barr virus and influenza A virus (CEF-Peptides) or left unstimulated. Furthermore, the concentration of spike-specific antibodies has been analyzed in patients.

Results

Our results indicate that hematologic malignancy patients developed a robust cellular immune response to SARS-CoV-2 vaccination comparable to that of healthy controls, and for certain T cell subtypes even higher. The most reactive T cells to SARS-CoV-2 spike peptides belonged to the CD4 and Tfh cell compartment, being median (IQR), 3.39 (1.41-5.92) and 2.12 (0.55-4.14) as a percentage of IFN- and TNF-producing Tfh cells in patients. In this regard, the immunomodulatory treatment of patients before the vaccination period seems important as it was strongly associated with a higher percentage of activated CD4 and Tfh cells. SARS-CoV-2- and CEF-specific T cell responses significantly correlated with each other. Compared to lymphoma patients, myeloma patients had an increased percentage of SARS-CoV-2-specific Tfh cells. T-SNE analysis revealed higher frequencies of γδT cells in patients compared to controls, especially in myeloma patients. In general, after vaccination, SARS-CoV-2-specific T cells were also detectable in patients without seroconversion.

Conclusion

Hematologic malignancy patients are capable of developing a SARS-CoV-2-specific CD4 and Tfh cellular immune response after vaccination, and certain immunomodulatory therapies in the period before vaccination might increase the antigen-specific immune response. A proper response to recall antigens (e.g., CEF-Peptides) reflects immune cellular functionality and might be predictive for generating a newly induced antigen-specific immune response as is expected after SARS-CoV-2 vaccination.

Follicular CD8+ T Cells Are Elevated in HIV Infection and Induce PD-L1 on B Cells

Follicular CD8+CXCR5+ T cells are a specialized CD8+ T cell subset with unique follicular-homing capabilities that have been reported to display effector functions in viral immunity, tumor immunity, and autoimmunity. CD8+CXCR5+ T cells exhibit B cell helper functions and express CD40L, ICOS, programmed cell death protein 1 (PD-1), and BCL-6, the transcriptional regulator of CD4+CXCR5+ T follicular helper cells and of germinal center B cells. HIV is known to be sequestered in lymphoid follicles, and CD8+CXCR5+ T cell frequency is a marker for disease severity, given that HIV-infected patients with lower numbers of circulating CD8+CXCR5+ T cells display lower CD4+ T cell counts. Likewise, several groups have reported a direct correlation between the quantity of CD8+CXCR5+ T cells and suppression of HIV viral load. In this study, we observed elevated absolute numbers of CD8+CXCR5+ and CD8+CXCR5+BCL-6+PD-1+ T cells in the blood of HIV-infected participants of the Multicenter AIDS Cohort Study. We further demonstrated in vitro that activated human CD8+CXCR5+ T cells isolated from peripheral blood and tonsil from healthy donors show increased CD40L expression and induce the production of PD ligand 1 (PD-L1)+IgG+ B cells. Moreover, absolute numbers of CD8+CXCR5+ T cells significantly and positively correlated with numbers of PD-L1+ B cells found in blood of HIV-infected individuals. Altogether, these results show that activated CD8+CXCR5+ T cells have the ability to activate B cells and increase the percentage of PD-L1+ and PD-L1+IgG+ B cells, which provides insights into the early events of B cell activation and differentiation and may play a role in disease progression and lymphomagenesis in HIV-infected individuals.

Phenotypes of peripheral CD4+ T helper cell subsets in pregnant women with HBeAg-negative chronic asymptomatic HBV carriers

Background

Chronic hepatitis B virus (HBV) infection is a major public health problem worldwide, and mother-to-child transmission is the key mode of HBV infection. CD4⁺ T helper (Th) cells play a critical role in the immune microenvironment of specific maternal tolerance to the foetus during pregnancy. However, the roles of Th cell subsets in pregnant women (PW) with chronic asymptomatic HBV carriers (ASCs) remain completely unclear. Here, we aimed to characterize CD4⁺ T-cell immunity in PW with hepatitis Be antigen (HBeAg)-negative chronic ASCs.

Methods

Human peripheral blood mononuclear cells (PBMCs) from PW without HBV infection or with chronic ASCs and healthy controls (HC) were isolated, and CD4⁺ Th cell subsets were detected by flow cytometry in addition to serum cytokines. Serological HBV markers, liver function and hormone levels of these individuals were also tested.

Results

The frequencies of circulating T follicular helper (Tfh) type 2 (Tfh2) cells were significantly evaluated, but Tfh1 cell frequencies were notably decreased in PW compared to HC. Moreover, the frequencies of Th22 cells were only notably increased in PW with chronic ASCs in comparison with PW. Additionally, increased levels of serum IL-4 were positively correlated with Tfh2 cell frequencies in healthy PW. Interestingly, serum P4 levels were positively associated with the frequencies of circulating Tfh2 or Th2 cells but were negatively related to the frequencies of circulating Tfh17 or Th17 cells in healthy PW. Although there were some changes in the other CD4⁺ Th cell frequencies and cytokine levels or other references, significant differences were not found among HC, healthy PW, PW with HBeAg-negative chronic ASCs.

Conclusion

CD4⁺ Th cell subsets played a critical role in the immune microenvironment of PW, and these findings provided potential evidence for why PW with chronic ASCs did not receive antenatal antiviral prophylaxis.

Dynamics of circulating follicular helper T cell subsets and follicular regulatory T cells in rheumatoid arthritis patients according to HLA-DRB1 locus

B cells, follicular helper T (Tfh) cells and follicular regulatory T (Tfr) cells are part of a circuit that may play a role in the development or progression of rheumatoid arthritis (RA). With the aim of providing further insight into this topic, here we evaluated the frequency of different subsets of Tfh and Tfr in untreated and long-term treated RA patients from a cohort of Argentina, and their potential association with particular human leukocyte antigen (HLA) class-II variants and disease activity. We observed that the frequency of total Tfh cells as well as of particular Tfh subsets and Tfr cells were increased in seropositive untreated RA patients. Interestingly, when analyzing paired samples, the frequency of Tfh cells was reduced in synovial fluid compared to peripheral blood, while Tfr cells levels were similar in both biological fluids. After treatment, a decrease in the CCR7^loPD1^hi Tfh subset and an increase in the frequency of Tfr cells was observed in blood. In comparison to healthy donors, seropositive patients with moderate and high disease activity exhibited higher frequency of Tfh cells while seropositive patients with low disease activity presented higher Tfr cell frequency. Finally, we observed that HLA-DRB1*09 presence correlated with higher frequency of Tfh and Tfr cells, while HLA-DRB1*04 was associated with increased Tfr cell frequency. Together, our results increase our knowledge about the dynamics of Tfh and Tfr cell subsets in RA, showing that this is altered after treatment.

Circulating plasmablasts and follicular helper T-cell subsets are associated with antibody-positive autoimmune epilepsy

Autoimmune epilepsy (AE) is an inflammatory disease of the central nervous system with symptoms that have seizures that are refractory to antiepileptic drugs. Since the diagnosis of AE tends to rely on a limited number of anti-neuronal antibody tests, a more comprehensive analysis of the immune background could achieve better diagnostic accuracy. This study aimed to compare the characteristics of anti-neuronal antibody-positive autoimmune epilepsy (AE/Ab(+)) and antibody-negative suspected autoimmune epilepsy (AE/Ab(-)) groups. A total of 23 patients who met the diagnostic criteria for autoimmune encephalitis with seizures and 11 healthy controls (HC) were enrolled. All patients were comprehensively analyzed for anti-neuronal antibodies; 13 patients were identified in the AE/Ab(+) group and 10 in the AE/Ab(-) group. Differences in clinical characteristics, including laboratory and imaging findings, were evaluated between the groups. In addition, the immunophenotype of peripheral blood mononuclear cells (PBMCs) and CSF mononuclear cells, particularly B cells and circulating Tfh (cTfh) subsets, and multiplex assays of serum and CSF were analyzed using flow cytometry. Patients with AE/Ab(+) did not show any differences in clinical parameters compared to patients with AE/Ab(-). However, the frequency of plasmablasts within PBMCs and CSF in patients with AE/Ab(+) was higher than that in patients with AE/Ab(-) and HC, and the frequency of cTfh17 cells and inducible T-cell co-stimulator (ICOS) expressing cTfh17 cells within cTfh subsets was higher than that in patients with AE/Ab(-). Furthermore, the frequency of ICOS^highcTfh17 cells was positively correlated with that of the unswitched memory B cells. We also found that IL-12, IL-23, IL-6, IL-17A, and IFN-γ levels were elevated in the serum and IL-17A and IL-6 levels were elevated in the CSF of patients with AE/Ab(+). Our findings indicate that patients with AE/Ab(+) showed increased differentiation of B cells and cTfh subsets associated with antibody production. The elevated frequency of plasmablasts and ICOS expressing cTfh17 shift in PBMCs may be indicative of the presence of antibodies in patients with AE.

The Third dose of CoronVac vaccination induces broad and potent adaptive immune responses that recognize SARS-CoV-2 Delta and Omicron variants

The waning humoral immunity and emerging contagious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants resulted in the necessity of the booster vaccination of coronavirus disease 2019 (COVID-19). The inactivated vaccine, CoronaVac, is the most widely supplied COVID-19 vaccine globally. Whether the CoronaVac booster elicited adaptive responses that cross-recognize SARS-CoV-2 variants of concern (VoCs) among 77 healthy subjects receiving the third dose of CoronaVac were explored. After the boost, remarkable elevated spike-specific IgG and IgA responses, as well as boosted neutralization activities, were observed, despite 3.0-fold and 5.9-fold reduced neutralization activities against Delta and Omicron strains compared to that of the ancestral strain. Furthermore, the booster dose induced potent B cells and memory B cells that cross-bound receptor-binding domain (RBD) proteins derived from VoCs, while Delta and Omicron RBD-specific memory B cell recognitions were reduced by 2.7-fold and 4.2-fold compared to that of ancestral strain, respectively. Consistently, spike-specific circulating follicular helper T cells (cTfh) significantly increased and remained stable after the boost, with a predominant expansion towards cTfh17 subpopulations. Moreover, SARS-CoV-2-specific CD4⁺ and CD8⁺ T cells peaked and sustained after the booster. Notably, CD4⁺ and CD8⁺ T cell recognition of VoC spike was largely preserved compared to the ancestral strain. Individuals without generating Delta or Omicron neutralization activities had comparable levels of CD4⁺ and CD8⁺ T cells responses as those with detectable neutralizing activities. Our study demonstrated that the CoronaVac booster induced broad and potent adaptive immune responses that could be effective in controlling SARS-CoV-2 Delta and Omicron variants.

Symbiotic bacteria-dependent expansion of MR1-reactive T cells causes autoimmunity in the absence of Bcl11b

MHC class I-related protein 1 (MR1) is a metabolite-presenting molecule that restricts MR1-reactive T cells including mucosal-associated invariant T (MAIT) cells. In contrast to MAIT cells, the function of other MR1-restricted T cell subsets is largely unknown. Here, we report that mice in which a T cell-specific transcription factor, B-cell lymphoma/leukemia 11B (Bcl11b), was ablated in immature thymocytes (Bcl11b^∆iThy mice) develop chronic inflammation. Bcl11b^∆iThy mice lack conventional T cells and MAIT cells, whereas CD4⁺IL-18R⁺ αβ T cells expressing skewed Traj33 (Jα33)⁺ T cell receptors (TCR) accumulate in the periphery, which are necessary and sufficient for the pathogenesis. The disorders observed in Bcl11b^∆iThy mice are ameliorated by MR1-deficiency, transfer of conventional T cells, or germ-free conditions. We further show the crystal structure of the TCR expressed by Traj33⁺ T cells expanded in Bcl11b^∆iThy mice. Overall, we establish that MR1-reactive T cells have pathogenic potential.

MiR-29a-3p negatively regulates circulating Tfh memory cells in patients with Graves’ disease by targeting ICOS

MicroRNAs (miRNAs) are small endogenous noncoding RNAs that regulate genome expression posttranscriptionally and are involved in autoimmune diseases. Previous studies have indicated that follicular helper T (Tfh) cells play a critical role in the pathogenesis of Graves' disease (GD). However, the molecular mechanisms that contribute to circulating Tfh memory cell response in GD patients remain incompletely understood. This study aimed to investigate the role of miRNAs on circulating Tfh memory cells in GD patients. Herein, our data showed that the proportion of circulating Tfh memory cells, the transcript levels of IL-21, and the plasma concentrations of IL-21 were increased in the peripheral blood from GD patients. We also found that inducible co-stimulator (ICOS) expression, an important molecule expressed on Tfh cells, were significantly augmented in the peripheral blood mononuclear cells (PBMCs) from GD patients and positively correlated with the percentage of circulating Tfh memory cells and the transcript levels of IL-21 in GD. Intriguingly, miRNA sequencing screened miR-29a-3p expression was downregulated and inversely correlated with ICOS expression and the frequency of circulating Tfh memory cells in patients with GD. Luciferase assay demonstrated that ICOS was the direct target gene of miR-29a-3p, and miR-29a-3p could inhibit ICOS at both transcriptional and translational levels. Overexpression of miR-29a-3p reduced the proportion of circulating Tfh memory cells. Moreover, miR-29a-3p expression negatively correlated with serum concentrations of TSH receptor antibody (TRAb) in GD patients. Collectively, our results demonstrate that miR-29a-3p emerges as a post-transcriptional brake to limit circulating Tfh memory cell response in GD patients and may be involved in the pathogenesis of GD.

Different antibody-associated autoimmune diseases have distinct patterns of T follicular cell dysregulation

Autoantibodies are produced within germinal centers (GC), in a process regulated by interactions between B, T follicular helper (Tfh), and T follicular regulatory (Tfr) cells. The GC dysregulation in human autoimmunity has been inferred from circulating cells, albeit with conflicting results due to diverse experimental approaches. We applied a consistent approach to compare circulating Tfr and Tfh subsets in patients with different autoimmune diseases. We recruited 97 participants, including 72 patients with Hashimoto's thyroiditis (HT, n = 18), rheumatoid arthritis (RA, n = 16), or systemic lupus erythematosus (SLE, n = 32), and 31 matched healthy donors (HD). We found that the frequency of circulating T follicular subsets differed across diseases. Patients with HT had an increased frequency of blood Tfh cells (p = 0.0215) and a reduced Tfr/Tfh ratio (p = 0.0338) when compared with HD. This was not observed in patients with systemic autoimmune rheumatic diseases (RA, SLE), who had a reduction in both Tfh (p = 0.0494 and p = 0.0392, respectively) and Tfr (p = 0.0003 and p = 0.0001, respectively) cells, resulting in an unchanged Tfr/Tfh ratio. Activated PD-1⁺ICOS⁺Tfh and CD4⁺PD-1⁺CXCR5^-Tph cells were raised only in patients with SLE (p = 0.0022 and p = 0.0054), without association with disease activity. Our data suggest that GC dysregulation, assessed by T follicular subsets, is not uniform in human autoimmunity. Specific patterns of dysregulation may become potential biomarkers for disease and patient stratification.

Distinct CD4+ T cell signature in ANA-positive young adult patients

Failure of immune tolerance can lead to autoantibody production resulting in autoimmune diseases, a broad spectrum of organ-specific or systemic disorders. Immune tolerance mechanisms regulate autoreactive T and B cells, yet some lymphocytes escape and promote autoantibody production. CD4+ T cell dysregulation, characterized by decreased or impaired regulatory cells (Tregs) and/or accumulation of memory and effector T cells such as TH17, plays a crucial role in the pathogenesis of these diseases. Antinuclear antibody (ANAs) testing is used as a first step for the diagnosis of autoimmune disorders, although most ANA-positive individuals do not have nor will develop an autoimmune disease. Studying the differences of T cell compartment among healthy blood donors, ANA-negative patients and ANA-positive patients, in which loss of tolerance have not led to autoimmunity, may improve our understanding on how tolerance mechanisms fail. Herein, we report that ANA-positive patients exhibit a distinct distribution of T cell subsets: significantly reduced frequencies of recent thymic emigrants (RTE) and naïve T cells, and significantly increased frequencies of central memory T cells, TH2 and TH17 cells; modulations within the T cell compartment are most profound within the 18-40 year age range. Moreover, CD4+ T cells in ANA-positive patients are metabolically active, as determined by a significant increase in mTORC1 and mTORC2 signals, compared to ANA-negative patients and healthy blood donors. No significant impairment of Treg numbers or pro-inflammatory cytokine production was observed. These results identify a unique T cell signature associated with autoantibody production in the absence of autoimmune disease.

Aberrant expansion of follicular helper T cell subsets in patients with systemic lupus erythematosus

Objective

Systemic lupus erythematosus (SLE) is a chronic and complex autoimmune disease characterized by multiple autoantibodies, resulting in multiple organ and tissue damages. These pathogenic autoantibodies produced by B cells are closely correlated with follicular helper T (Tfh) cell subsets that play a fundamental role in the pathogenesis of SLE. The aim of the present study was to study the phenotype and role of circulating Tfh (cTfh) cell subsets and associated B cell subpopulations in active and inactive SLE patients.

Methods

Thirty SLE outpatients and 24 healthy controls (HCs) were enrolled in this study. The frequency of cTfh cell and B cell subsets in peripheral blood mononuclear cells (PBMCs) and the plasma levels of eight cytokines were determined by flow cytometry, and plasma IL-21 levels were measured by ELISA. Meanwhile, we used MRL/lpr mice as the model of SLE to research the alterations of Tfh cells in the thymus and spleen of mice.

Results

Frequencies of CD4⁺CXCR5⁺CD45RA^-effector cTfh cells, PD1⁺cTfh, PD1⁺ICOS⁺cTfh, PD1⁺cTfh1, PD1⁺cTfh2, PD1⁺cTfh17, and PD1⁺ICOS⁺cTfh1 cells as well as plasmablasts showed significant differences among HC, active and inactive SLE patients. Moreover, cytokines typically associated with cTfh cells, including IL-6 and IL-21, were elevated in active SLE patients compared to inactive SLE patients and HCs. Additionally, a positive correlation was observed between PD1⁺ICOS⁺ cTfh or PD1⁺ICOS⁺ cTfh1 cell frequencies and plasmablasts or IL-21 levels, as well as between plasmablasts. We also found PD1⁺ICOS⁺ Tfh cells expansion in both thymus and spleen of MRL/lpr mice, accompanied by increased frequencies in B cells and plasmablasts, meanwhile, cTfh1which expressing IFN-γ was increased in the peripheral blood of MRL/lpr mice.

Conclusion

Tfh cell subsets and plasmablasts may play a fundamental role in the pathogenesis of SLE and may provide potential targets for therapeutic interventions for SLE.

Identification of CD4+ T cells with T follicular helper cell characteristics in the pig

T follicular helper (Tfh) cells provide help to germinal center B cells for affinity maturation, class switch and memory formation. Despite these important functions, this subset has not been studied in detail in pigs due to a lack of species-specific antibodies. We investigated putative Tfh cells from lymphoid tissues and blood of healthy pigs by using cross-reactive antibodies for inducible T-cell costimulator (ICOS) and B-cell lymphoma 6 (Bcl-6). In lymph nodes, we identified a CD4⁺ T cell population with an ICOS⁺Bcl-6⁺CD8α⁺ phenotype, reminiscent of human and murine germinal center Tfh cells. Within blood-derived CD4⁺ T cells, sorted ICOS^hiCD25^- and ICOS^dimCD25^dim cells were able to induce the differentiation of CD21⁺IgM⁺ B cells into Ig-secreting plasmablasts. Compared to naïve CD4⁺ T cells, these two phenotypes were 3- to 7-fold enriched for cells expressing the Tfh-related transcripts CD28, CD40LG, IL6R and MAF, as identified by single-cell RNA sequencing. These results provide a first characterization of Tfh cells in swine and confirm their ability to provide B-cell help.

Heterogeneity of circulating CD4+CD8+ double-positive T cells characterized by scRNA-seq analysis and trajectory inference

The frequency of CD4⁺CD8⁺ double-positive (DP) T cells is highly associated with a variety of diseases. Recently, we used high-throughput single-cell RNA sequencing to show that circulating DP T cells in cynomolgus monkeys comprise nine heterogeneous populations. To better understand the characteristics of DP T cells, we analyzed 7601 cells from a rhesus monkey and detected 14,459 genes. Rhesus monkey DP T cells comprised heterogeneous populations (naïve, Treg-, Tfh-, CCR9⁺ Th-, Th17-, Th2-, Eomes⁺ Tr1-, CTL-, PLZF⁺ innate- and Eomes⁺ innate-like cells) with multiple potential functions. We also identified two new subsets using aggregated scRNA-seq datasets from the rhesus and the cynomolgus monkey: CCR9⁺ Th-like cells expressing ICAM2 and ITGA1, and PLZF⁺ innate-like cells that display innate-associated gene signatures such as ZBTB16, TYROBP, MAP3K8, and KLRB1. Trajectory inference of cell differentiation status showed that most DP T cells in the rhesus monkey were found in the mid-to-late pseudotime, whereas DP T cells from the cynomolgus monkey were found in early pseudotime. This suggests that DP T cells in rhesus monkeys may exhibit more diverse differentiation states than those in cynomolgus monkeys. Thus, scRNA-seq and trajectory inference identified a more diverse subset of the circulating DP T cells than originally thought.

CD8 lymphocytes mitigate HIV-1 persistence in lymph node follicular helper T cells during hyperacute-treated infection

HIV persistence in tissue sites despite ART is a major barrier to HIV cure. Detailed studies of HIV-infected cells and immune responses in native lymph node tissue environment is critical for gaining insight into immune mechanisms impacting HIV persistence and clearance in tissue sanctuary sites. We compared HIV persistence and HIV-specific T cell responses in lymph node biopsies obtained from 14 individuals who initiated therapy in Fiebig stages I/II, 5 persons treated in Fiebig stages III-V and 17 late treated individuals who initiated ART in Fiebig VI and beyond. Using multicolor immunofluorescence staining and in situ hybridization, we detect HIV RNA and/or protein in 12 of 14 Fiebig I/II treated persons on suppressive therapy for 1 to 55 months, and in late treated persons with persistent antigens. CXCR3+ T follicular helper cells harbor the greatest amounts of gag mRNA transcripts. Notably, HIV-specific CD8+ T cells responses are associated with lower HIV antigen burden, suggesting that these responses may contribute to HIV suppression in lymph nodes during therapy. These results reveal HIV persistence despite the initiation of ART in hyperacute infection and highlight the contribution of virus-specific responses to HIV suppression in tissue sanctuaries during suppressive ART.

Impact of Corticosteroids on the Proportions of Circulating Tfh Cell Subsets in Patients With Systemic Lupus Erythematous

Objectives

This study aimed to analyze the distribution of T follicular helper (Tfh) cells in lupus patients, and the effects of steroids on circulating Tfh cells.

Methods

Circulating Tfh cell subsets were defined by multicolor flow cytometry as Tfh17, Tfh2 or Tfh1 subpopulations of CXCR5⁺CD45RA^–CD4⁺ T cells in the peripheral blood of SLE patients and healthy controls. To test the effects of corticosteroid on Tfh cells, PBMC harvested from both SLE and healthy controls were cocultured with dexamethasone, and then analyzed by Flow cytometry.

Results

The proportion of Tfh17 cells in SLE patients was increased significantly compared with healthy controls. Additionally, patients with an active disease had reduced Tfh1 subsets than those with an inactive disease and healthy controls. The frequency of Tfh2 cells was associated with the proportion of circulating plasmablasts and the amount of anti-dsDNA. Dexamethasone reduced the percentage of Tfh2 cells while increased the proportion of Tfh17 subset in gated CXCR5⁺CD45RA^–CD4⁺ T cells.

Conclusion

Our study investigated the distribution of circulating Tfh subsets in lupus patients. Corticosteroids treatment not only down-regulated the proportion of circulating Tfh cells, but also altered the distribution of Tfh subsets in vivo and in vitro.

Inactivated whole-virion vaccine BBV152/Covaxin elicits robust cellular immune memory to SARS-CoV-2 and variants of concern

BBV152 is a whole-virion inactivated vaccine based on the Asp614Gly variant. BBV152 is the first alum-imidazoquinolin-adjuvanted vaccine authorized for use in large populations. Here we characterized the magnitude, quality and persistence of cellular and humoral memory responses up to 6 months post vaccination. We report that the magnitude of vaccine-induced spike and nucleoprotein antibodies was comparable with that produced after infection. Receptor binding domain-specific antibodies declined against variants in the order of Alpha (B.1.1.7; 3-fold), Delta (B.1.617.2; 7-fold) and Beta (B.1.351; 10-fold). However, pseudovirus neutralizing antibodies declined up to 2-fold against the Delta followed by the Beta variant (1.7-fold). Vaccine-induced memory B cells were also affected by the Delta and Beta variants. The SARS-CoV-2-specific multicytokine-expressing CD4⁺ T cells were found in ~85% of vaccinated individuals. Only a ~1.3-fold reduction in efficacy was observed in CD4⁺ T cells against the Beta variant. We found that antigen-specific CD4⁺ T cells were present in the central memory compartment and persisted for at least up to 6 months post vaccination. Vaccine-induced CD8⁺ T cells were detected in ~50% of individuals. Importantly, the vaccine was capable of inducing follicular T helper cells that exhibited B-cell help potential. These findings show that inactivated vaccine BBV152 induces robust immune memory to SARS-CoV-2 and variants of concern that persists for at least 6 months after vaccination.

An intranasally administrated SARS-CoV-2 beta variant subunit booster vaccine prevents beta variant replication in rhesus macaques

Emergence of SARS-CoV-2 variants and waning of vaccine/infection-induced immunity pose threats to curbing the COVID-19 pandemic. Effective, safe, and convenient booster vaccines are in need. We hypothesized that a variant-modified mucosal booster vaccine might induce local immunity to prevent SARS-CoV-2 infection at the port of entry. The beta-variant is one of the hardest to cross-neutralize. Herein, we assessed the protective efficacy of an intranasal booster composed of beta variant-spike protein S1 with IL-15 and TLR agonists in previously immunized macaques. The macaques were first vaccinated with Wuhan strain S1 with the same adjuvant. A total of 1 year later, negligibly detectable SARS-CoV-2-specific antibody remained. Nevertheless, the booster induced vigorous humoral immunity including serum- and bronchoalveolar lavage (BAL)-IgG, secretory nasal- and BAL-IgA, and neutralizing antibody against the original strain and/or beta variant. Beta-variant S1-specific CD4⁺ and CD8⁺ T cell responses were also elicited in PBMC and BAL. Following SARS-CoV-2 beta variant challenge, the vaccinated group demonstrated significant protection against viral replication in the upper and lower respiratory tracts, with almost full protection in the nasal cavity. The fact that one intranasal beta-variant booster administrated 1 year after the first vaccination provoked protective immunity against beta variant infections may inform future SARS-CoV-2 booster design and administration timing.

Clonal evolution and TCR specificity of the human TFH cell response to Plasmodium falciparum CSP

T follicular helper (T_FH) cells play a crucial role in the development of long-lived, high-quality B cell responses after infection and vaccination. However, little is known about how antigen-specific T_FH cells clonally evolve in response to complex pathogens and what guides the targeting of different epitopes. Here, we assessed the cell phenotype, clonal dynamics, and T cell receptor (TCR) specificity of human circulating T_FH (cT_FH) cells during successive malaria immunizations with radiation-attenuated Plasmodium falciparum (Pf) sporozoites. Repeated parasite exposures induced a dynamic, polyclonal cT_FH response with high frequency of cells specific to a small number of epitopes in Pf circumsporozoite protein (PfCSP), the primary sporozoite surface protein and well-defined vaccine target. Human leukocyte antigen (HLA) restrictions and differences in TCR generation probability were associated with differences in the epitope targeting frequency and indicated the potential of amino acids 311 to 333 in the Th2R/T* region as a T cell supertope. But most of vaccine-induced anti-amino acid 311 to 333 TCRs, including convergent TCRs with high sequence similarity, failed to tolerate natural polymorphisms in their target peptide sequence, thus demonstrating that the T_FH cell response was limited to the vaccine strain. These data suggest that the high parasite diversity in endemic areas will limit boosting of the vaccine-induced T_FH cell response by natural infections. Our findings may guide the further design of PfCSP-based malaria vaccines able to induce potent T helper cell responses for broad, long-lasting antibody responses.

Bupi Yichang Pill alleviates dextran sulfate sodium-induced ulcerative colitis in mice by regulating the homeostasis of follicular helper T cells

BACKGROUND

Follicular helper T (Tfh) cells-based therapy represents a new treatment option for inflammatory bowel disease. Bupi Yichang Pill (BPYCP), a traditional Chinese formula for the treatment of dysentery and diarrhea, exhibits potential anti-inflammatory activities in treating various kinds of inflammation. However, its anti-inflammatory effect on colitis and the underlying mechanisms remain unknown.

PURPOSE

To explore the protective role and underlying immunomodulatory effects of BPYCP in the treatment of UC.

METHODS

The dextran sodium sulfate (DSS) free-drinking method induced UC in C57BL/6 mice, and BPYCP was orally administrated at a dosage of 1.5, 3.0, or 6.0 g/kg/day. Throughout the experimental period, the effects of BPYCP on DSS-induced clinical symptoms and disease activity index (DAI) were monitored and analyzed. Hematoxylin-eosin staining was used to observe the histopathological injury of the colon. Flow cytometry was used to detect the levels of Tfh cells, Tfh cell subpopulations, and memory Tfh cells. ELISA, Western blot, and qRT-PCR were used to detect the expression of inflammatory cytokines and Tfh cell-related biomarkers.

RESULTS

Medium and high dosages of BPYCP effectively alleviated DSS-induced experimental colitis with increased body weight, survival rate and colonic length, and decreased DAI, colonic weight, and colonic index, as well as less ulcer formation and inflammatory cell infiltration, increased anti-inflammatory cytokine IL-10, and decreased pro-inflammatory cytokines IL-17A, IL-6, and TNF-ɑ. Moreover, BPYCP administration significantly decreased the percentage of Tfh cells and the expression of Tfh markers ICOS, PD-1 and Bcl-6 in the mesenteric lymph nodes of colitis mice. In addition, BPYCP treatment obviously decreased the percentages of Tfh1, Tfh17 and Tem-Tfh cells and upregulated Tfr cells in colitis mice. However, there were no significant regulatory effects of BPYCP on Tfh cell response in normal mice.

CONCLUSION

Taken together, these results demonstrated a protective effect of BPYCP against DSS-induced experimental colitis by regulating Tfh cell homeostasis.

Members of the Regulatory Lymphocyte Club in Common Variable Immunodeficiency

The role of CD4 T regulatory cells is well established in peripheral tolerance and the pathogenesis of the murine model and human autoimmune diseases. CD4 T regulatory cells (CD4 Tregs) have been investigated in common variable immunodeficiency (CVID). Recently, additional members have been added to the club of regulatory lymphocytes. These include CD8 T regulatory (CD8 Tregs), B regulatory (Bregs), and T follicular helper regulatory (T_FR) cells. There are accumulating data to suggest their roles in both human and experimental models of autoimmune disease. Their phenotypic characterization and mechanisms of immunoregulation are evolving. Patients with CVID may present or are associated with an increased frequency of autoimmunity and autoimmune diseases. In this review, we have primarily focused on the characteristics of CD4 Tregs and new players of the regulatory club and their changes in patients with CVID in relation to autoimmunity and emphasized the complexity of interplay among various regulatory lymphocytes. We suggest future careful investigations of phenotypic and functional regulatory lymphocytes in a large cohort of phenotypic and genotypically defined CVID patients to define their role in the pathogenesis of CVID and autoimmunity associated with CVID.

Sirolimus therapy restores the PD-1+ICOS+Tfh:CD45RA-Foxp3high activated Tfr cell balance in primary Sjögren's syndrome

BACKGROUND

Primary Sjögren's syndrome (pSS) is a common chronic autoimmune disease characterized by lymphocytic infiltration of salivary and lacrimal glands. The current study was performed to investigate the roles of follicular helper T (Tfh) and follicular regulatory T (Tfr) subsets in patients with pSS, and to evaluate the effects of sirolimus on these cells.

METHODS

Levels of circulating Tfh and Tfr subsets in 58 pSS patients and 26 healthy controls (HC) were determined by flow cytometry. These T cell subsets were also analyzed in 12 patients before and after treatment with sirolimus. Clinical features and correlations with follicular T cells were analyzed systematically. The discriminative ability of the cells and ratios was evaluated based on the area under the receiver operating characteristic curves.

RESULTS

Patients with pSS had higher percentage and absolute number of PD-1+ICOS+Tfh cells, while lower percentage and absolute number of Tfr, activated regulatory T (aTreg) cells, and CD45RA-Foxp3^high activated Tfr cells. Furthermore, increased number of PD-1+ICOS+Tfh cells was associated with B cells, while decreased numbers of Tfr and their subsets was strongly associated with aTreg cells in pSS patients. Also, the higher proportion of PD-1+ICOS+Tfh cells was positively correlated with higher level of autoantibodies, ESR, IgG, cytokines (IL-2, IL-4, IL-10, IL-17, IFN-γ, TNF-α, IL-21 and sIL-2αR), and disease activity. Unexpectedly, the elevated PD-1+ICOS+Tfh:CD45RA-Foxp3^high activated Tfr ratio had the greatest ability to discriminate between pSS and HC, and sirolimus therapy restored the PD-1+ICOS+Tfh cells:CD45RA-Foxp3^high activated Tfr ratio, and controlled disease activity.

CONCLUSION

The novel ratio of PD-1+ICOS+Tfh to CD45RA-Foxp3^high activated Tfr cells can effectively discriminate the pSS patients from controls, and Tfr cell subsets may resemble Treg cell lineages. Furthermore, the PD-1+ICOS+Tfh cells can be used as a biomarker of disease activity and to verify the therapeutic effects of sirolimus in pSS.

Abnormal Shift in B Memory Cell Profile Is Associated With the Expansion of Circulating T Follicular Helper Cells via ICOS Signaling During Acute HIV-1 Infection

Interactions between T follicular helper (Tfh) cells and germinal center B cells are essential for the differentiation of B cells and specific antibody responses against HIV-1 infection. However, the extent to which HIV-1 infection affects the dynamic interplay between these two cell populations in the bloodstream remains unclear. In this study, the dynamics of circulating Tfh (cTfh) and B cells and their relationship in individuals with acute and chronic HIV-1 infection were investigated. Twenty-five study subjects were enrolled from the Beijing PRIMO clinical cohort, a prospective cohort of HIV-1-negative men who have sex with men (MSM) for the identification of cases of acute HIV-1 infection (AHI) at Beijing Youan Hospital, Capital Medical University. Individuals with AHI were selected at random. Matched samples were also collected and analyzed from the same patients with chronic HIV-1 infection. None of the study subjects received antiretroviral therapy during acute or chronic infection. Multicolor flow cytometry was used for the immunophenotypic and functional characterization of cTfh cell and B cell subsets. AHI resulted in increased proportions in bulk cTfh, ICOS⁺cTfh or IL-21⁺ICOS⁺cTfh cells. In both acute and chronic infections, activated memory (AM), tissue-like memory (TLM), and plasmablast (PB) B cell levels were increased whilst resting memory (RM) and naïve mature (NM) B cell levels were decreased. Classical memory (CM) B cells were unaffected during infection. Association analyses showed that the levels of ICOS⁺cTfh and IL-21⁺ICOS⁺cTfh cells were negatively correlated with those of AM, CM, RM cells, and positively correlated with those of NM cells in AHI but not chronic HIV-1 infection stage (CHI). Moreover, the frequency of IL-21⁺ICOS⁺cTfh cells was also positively correlated with plasma HIV-1 viral load, and had an opposite association trend with CD4⁺T cell count in AHI. Our data suggests that HIV-1 infection drives the expansion of cTfh cells, which in turn leads to perturbations of B cell differentiation through ICOS signaling during acute infection stage. These findings provide insight on the role of ICOS in the regulation of cTfh/B cell interaction during AHI and may potentially guide the design of effective strategies for restoring anti-HIV-1 immunity in the infected patients.

Antibody Therapies in Autoimmune Neuromuscular Junction Disorders: Approach to Myasthenic Crisis and Chronic Management

Myasthenia gravis (MG) is a neurological autoimmune disorder characterized by muscle weakness and fatigue. It is a B cell-mediated disease caused by pathogenic antibodies directed against various components of the neuromuscular junction (NMJ). Despite the wide range of adverse effects, current treatment is still based on non-specific immunosuppression, particularly on long-term steroid usage. The increasing knowledge regarding the pathogenic mechanisms of MG has however allowed to create more target-specific therapies. A very attractive therapeutic approach is currently offered by monoclonal antibodies (mAbs), given their ability to specifically and effectively target different immunopathological pathways, such as the complement cascade, B cell-related cluster of differentiation (CD) proteins, and the human neonatal Fc receptor (FcRn). Up to now, eculizumab, a C5-directed mAb, has been approved for the treatment of generalized MG (gMG) and efgartigimod, a FcRn inhibitor, has just been approved by the U.S. Food and Drug Administration for the treatment of anti-acetylcholine receptor (AChR) antibody positive gMG. Other mAbs are currently under investigation with encouraging preliminary results, further enriching the new range of therapeutic possibilities for MG. This review article provides an overview of the present status of mAb-based therapies for MG, which offer an exciting promise for better outcomes by setting the basis of a precision medicine approach.

The link between circulating follicular helper T cells and autoimmunity

Follicular helper T (T_FH) cells provide help to B cells, supporting the formation of germinal centres that allow affinity maturation of antibody responses. Although usually located in secondary lymphoid organs, T cells bearing features of T_FH cells can also be identified in human blood, and their frequency and phenotype are often altered in people with autoimmune diseases. In this Perspective article, I discuss the increase in circulating T_FH cells seen in autoimmune settings and explore potential explanations for this phenomenon. I consider the multistep regulation of T_FH cell differentiation by the CTLA4 and IL-2 pathways as well as by regulatory T cells and highlight that these same pathways are crucial for regulating autoimmune diseases. The propensity of infection to serve as a cue for T_FH cell differentiation and a potential trigger for autoimmune disease development is also discussed. Overall, I postulate that alterations in pathways that regulate autoimmunity are coupled to alterations in T_FH cell homeostasis, suggesting that this population may serve as a core sentinel of dysregulated immunity.

Adaptive immune cell responses as therapeutic targets in antibody-mediated organ rejection

Humoral alloimmunity of organ transplant recipient to donor can lead to antibody-mediated rejection (ABMR), causing thousands of organ transplants to fail each year worldwide. However, the mechanisms of adaptive immune cell responses at the basis of humoral alloimmunity have not been entirely understood. In this review, we discuss how recent investigations have uncovered the key contributions of T follicular helper (T_FH) and B cells and their coordinated actions in driving donor-specific antibody generation and immune progression towards ABMR. We show how recognition of the role of T_FH-B cell interactions may allow the elaboration of improved clinical strategies for immune monitoring and the identification of novel therapeutic targets to tackle ABMR that will ultimately improve organ transplant survival.