B cells alter the phenotype and function of follicular-homing CXCR5+ T cells

The CXC chemokine receptor (CXCR)5 is rapidly induced on activated CD4(+) T cells, allowing migration toward secondary lymphoid tissue follicles, where the CXCR5 ligand CXCL13/BCA-1 is produced. Such CXCR5(+) T cells provide efficient help for B cell immunoglobulin production and are termed follicular B helper T (T(FH)) cells. However, the molecular mechanisms by which T(FH) cells provide B cell help are unknown. Here, we demonstrate that newly generated (antigen-primed) T(FH) cells express a phenotype consistent with induction of B cell proliferation, but co-culture with primed B cells resulted in a switch to a plasma cell-inducing phenotype, characterized by loss of CD154, induction of CD70 and an increase in IL-10 production capacity. The ability to produce IL-10 could be maintained as a stable phenotype, but its secretion was strictly dependent on inducible costimulator (ICOS) signaling. Furthermore, B cells preserved a lymph node migration phenotype in proliferating T(FH) cells by preventing the loss of CC chemokine receptor (CCR)7 and the induction of CCR5. Thus, B cells directly modulate the B cell helper phenotype in T(FH) cells and actively promote their prolonged co-localization with these cells.     

Regulation of Na+/H+ exchanger in dendritic cells by Akt2

Dendritic cells (DCs) are antigen-presenting cells decisive in primary immune responses and establishment of immunological memory. They are activated by bacterial lipopolysaccharides (LPS), which lead to activation of Na⁺/H⁺ exchanger activity, cell swelling, reactive oxygen species (ROS) formation, and migration. The effects require functional phosphoinositide 3 kinase and are paralleled by Akt phosphorylation. The present study explored the putative involvement of the Akt isoform Akt2. To this end, experiments were performed in DCs isolated from bone marrow of mice lacking functional Akt2/PKB? (akt2 ^−/−) and respective wild-type animals (akt2 ^+/+). Based on BCECF fluorescence, cytosolic pH (pH_i) was significantly lower in akt2 ^−/− than in akt2 ^+/+ DCs. Transient exposure to NH₄Cl was followed by profound cytosolic acidification in both genotypes. Subsequent re-alkalinization was largely dependent on Na⁺ thus reflecting Na⁺/H⁺ exchanger activity and was significantly lower in akt2 ^−/− than in akt2 ^+/+ DCs. According to forward scatter in FACS analysis, cell volume was significantly lower in akt2 ^−/− than in akt2 ^+/+ DCs. Exposure of DCs to LPS led within 4 h to significant increases of Na⁺/H⁺ exchanger activity, cell volume, ROS production, and migration in akt2 ^+/+ mice, and its effects were significantly blunted in akt2 ^−/− DCs. The present observations disclose a role of Akt2 in the regulation of pH_i, cell volume, ROS production, and migration in dendritic cells.     

Functional plasticity of human respiratory tract dendritic cells: GM-CSF enhances T(H)2 development

BACKGROUND: Dendritic cells within the human respiratory mucosa (RTDCs) are proposed to initiate immune responses to foreign antigens. Their capacity to polarize T-cell responses, however, has not been investigated. OBJECTIVE: To compare RTDCs with peripheral blood dendritic cells (PBDCs) with regard to phenotype, cytokine production, capacity to polarize T-cell responses, and effects of exposure to the pleiotropic cytokine, GM-CSF. METHODS: CD1a(+) RTDCs and CD1c(+) PBDCs were purified from nasal turbinates of patients with nonatopic rhinitis and peripheral blood of healthy individuals, respectively. In some experiments, matched CD1c(+) RTDCs and PBDCs from patients with rhinitis were compared. The phenotype of DC was examined by flow cytometry and cytokine production by cytometric bead array. DCs were cocultured with allogeneic naive CD4(+) T cells, and cytokine production was determined by immunophenotyping, cytometric bead array, and ELISA. RESULTS: Both RTDCs and PBDCs exhibited an immature phenotype, but RTDCs expressed lower levels of MHC class II antigen. Cross-linking of CD40 on PBDCs, but not RTDCs, induced production of IL-12p70. In mixed lymphocyte cultures, RTDCs induced a T(H)1/T(H)2 profile, whereas PBDCs induced a T(H)1 profile. Exposure of RTDCs to GM-CSF induced a T(H)2 pattern of response in the mixed lymphocyte cultures. In contrast, exposure of PBDCs to GM-CSF promoted a T(H)1 response. CONCLUSION: This report emphasizes the importance of studying tissue-derived primary DCs, demonstrates functional plasticity of RTDCs, and implicates GM-CSF in amplifying the potential of RTDCs to initiate T(H)2 responses in the airways.     

Dysregulation of circulating CD4+CXCR5+ T cells in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is characterized by a chronic low‐grade inflammatory state. Follicular helper T cells (Tfh) play critical roles in inducing B‐cell activation and producing various cytokines, whereas circulating CD4+CXCR5+ T cells (CTfh) may act as a counterpart to measure Tfh cell disorders. In this study, we investigated whether Tfh could be involved in the development of T2DM by assessing CTfh in peripheral blood. CTfh and it subtypes were determined by measuring CD3, CD4, CXCR5, CXCR3, and CCR6 in 68 T2DM patients and 60 healthy controls using flow cytometry. Results showed that proportion of CTfh in the peripheral CD4+ T cells was significantly increased in T2DM patients (8.5 ± 0.5%) than in controls (4.5 ± 0.3%) (p < 0.001). Further study revealed that the balance of CTfh subtypes was greatly dysregulated, in which percentage of Th17 subtype was significantly increased in patients. Investigating the correlation between CTfh and risk factors of T2DM demonstrated that proportion of CTfh were significantly elevated in patients with body mass index (BMI) over 24.0 (p = 0.005). Interestingly, patients with abdominal obesity had further increase in CTfh than those without abdominal obesity. This study suggests the involvement of CTfh in T2DM, especially in T2DM‐related obesity.     

Abundant expression of CXCL9 (MIG) by stromal cells that include dendritic cells and accumulation of CXCR3+ T cells in lymphocyte-rich gastric carcinoma

The neoplastic environment is generally regarded as an immunosuppressive milieu. However, a group of cancers are characterized by the abundance of tumour-infiltrating lymphocytes (TILs). Here we examined the possible roles of chemokines in the formation of lymphoid stroma in lymphocyte-rich gastric carcinomas (GCs), including EBV(+) cases and conventional GCs. Regardless of EBV positivity, TILs in lymphocyte-rich GCs predominantly expressed CXCR3, while its ligand CXCL9 was abundantly expressed by stromal cells and a portion of cancer cells. CXCL9(+) stromal cells were judged to include dendritic cells, because they partly co-expressed fascin, DC-sign, CD83, DC-lamp or HLA-DR. T cells in close contact with CXCL9(+) cells showed frequent labelling of Ki-67 (approximately 10%), suggesting the immunostimulatory activity of CXCL9(+) stromal cells. The T-cell zone of the regional lymph nodes of lymphocyte-rich GCs also abounded with CXCR3(+) T cells and CXCL9(+) stromal cells. This indicated a close similarity between cancer stroma and regional lymph nodes of lymphocyte-rich GCs. Quantitative RT-PCR also confirmed the strong expression of CXCR3, CXCL9 and IFNgamma in lymphocyte-rich GCs. In contrast, conventional GCs contained less abundant CXCR3(+) T cells and few CXCL9(+) stromal cells. Collectively, the CXCL9-CXCR3 axis plays a pivotal role in the formation of lymphoid stroma in lymphocyte-rich GCs. Given similar findings in the regional lymph nodes, the lymphoid stroma of lymphocyte-rich GCs may represent a tertiary lymphoid tissue with predominantly Th1-shifted immune responses.     

The influence of paediatric HIV infection on circulating B cell subsets and CXCR5+ T helper cells

Antiretroviral therapy (ART) only partially restores HIV‐induced alterations in lymphocyte populations. We assessed B and T cell phenotypes in a cohort of children from a single centre in the United Kingdom with perinatally acquired HIV compared to healthy controls. The majority of HIV infected children (44 of 56) were on fully suppressive combination ART. Children with perinatally acquired HIV had significantly lower memory B and CD4⁺CD45RO⁺CXCR5⁺ [follicular T helper cell (Tfh)‐like] T cell percentages. Detectable viraemia was associated with higher CD21^– (activated and exhausted/tissue‐like memory) B cells. A greater proportion of life spent on suppressive ART was associated with higher memory B cell percentages. These results suggest that early and sustained suppressive ART may preserve B and T cell phenotypes in perinatally acquired HIV and limit deficits in humoral immunity. A lower proportion of circulating Tfh‐like cells in HIV infected children appears to be independent of HIV treatment history and ongoing HIV viraemia and warrants further investigation.     

Contribution of FoxP3+ Tfr cells to overall human blood CXCR5+ T cells

The identification that T follicular helper (Tfh) cells is critical for the emergence of germinal centre responses prompted the study of CXCR5-expressing CD4⁺ T cell subsets in autoimmunity. However, circulating CXCR5-expressing T cells are heterogeneous by containing Forkhead box protein 3 (FoxP3)⁺ T follicular regulatory (Tfr) cells in addition to bona fide Tfh cells. Such heterogeneity may hamper the analysis of the contribution of specific follicular T cell subsets for autoimmune pathogenesis. Therefore, separate assessment of Tfh and Tfr populations offer greater opportunities for stratification of autoimmune patients, such as Sjögren’s syndrome patients.     

CD4+CXCR3+ T cells and plasmacytoid dendritic cells drive accelerated atherosclerosis associated with systemic lupus erythematosus

Cardiovascular disease due to accelerated atherosclerosis is the leading cause of death in patients with systemic lupus erythematosus (SLE). Noteworthy, accelerated atherosclerosis in SLE patients appears to be independant of classical Framingham risk factors. This suggests that aggravated atherosclerosis in SLE patients may be a result of increased inflammation and altered immune responses. However, the mechanisms that mediate the acceleration of atherosclerosis in SLE remain elusive. Based on experimental data which includes both humans (SLE patients and control subjects) and rodents (ApoE−/− mice), we herein propose a multi-step model in which the immune dysfunction associated with SLE (i.e. high level of IFN-α production by TLR 9-stimulated pDCs) is associated with, first, an increased frequency of circulating pro inflammatory CD4+CXCR3+ T cells; second, an increased production of CXCR3 ligands by endothelial cells; third, an increased recruitment of pro-inflammatory CD4+CXCR3+ T cells into the arterial wall, and fourth, the development of atherosclerosis. In showing how SLE may promote accelerated atherosclerosis, our model also points to hypotheses for potential interventions, such as pDCs-targeted therapy, that might be studied in the future.     

Regulation of antigen-expressing dendritic cells by double negative regulatory T cells

TCRαβ(+) CD3(+) CD4(-) CD8(-) NK1.1(-) double negative (DN) Tregs comprise 1-3% of peripheral T lymphocytes in mice and humans. It has been demonstrated that DN Tregs can suppress allo-, xeno- and auto-immune responses in an Ag-specific fashion. However, the mechanisms by which DN Tregs regulate immune responses remain elusive. Whether DN Tregs can regulate DCs has not been investigated previously. In this study, we demonstrate that DN Tregs express a high level of CTLA4 and are able to down-regulate costimulatory molecules CD80 and CD86 expressed on Ag-expressing mature DCs (mDCs). DN Tregs from CTLA4 KO mice were not able to downregulate CD80 and CD86 expression, indicating that CTLA4 is critical for DN Treg-mediated downregulation of costimulatory molecule expression on Ag-expressing mature DCs. Furthermore, DN Tregs could kill both immature and mature allogeneic DCs, as well as Ag-loaded syngeneic DCs, in an Ag-specific manner in vitro and in vivo, mainly through the Fas-FasL pathway. These data demonstrate, for the first time, that DN Tregs are potent regulators of DCs and may have the potential to be developed as a novel immune suppression treatment.     

Increased CD4+CXCR5+T follicular helper cells in diabetic nephropathy

Background: T follicular helper (Tfh) cells are known to regulate humoral immune response. In this study we examined the correlation of different subsets of peripheral blood Tfh cells in patients with diabetic nephropathy (DN). Methods: A total of 23 DN patients and 15 healthy controls (HC) were investigated for various subsets of Tfh cells by flow cytometry. The molecules ICOS⁺, PD-1⁺, CD28⁺, CD154⁺, IL-21⁺, IFN-γ⁺, IL-4⁺, IL-17⁺ Tfh cells were examined. The subsets of B cells were investigated by flow cytometry. The levels of 24?h urinary protein and estimated glomerular filtration rate (eGFR) were calculated. A potential correlation between the number of different subsets of Tfh cells, B cells and DN, was assessed. Results: The circulating CD4⁺CXCR5⁺PD-1⁺, PD-1⁺CD154⁺, PD-1⁺CD28⁺, PD-1⁺IL-21⁺, PD-1⁺IL-4⁺, PD-1⁺-IL-17⁺-Tfh cell counts, CD38⁺CD19⁺, CD38⁺CD19⁺CD40⁺ B cells and plasma levels of IL-21 were significantly increased in DN patients (p?+CXCR5⁺PD-1⁺ Tfh cell counts negatively correlated with eGFR; Tfh cell counts positively correlated with 24?h urinary protein concentration in DN patients. Post-treatment, there was a significant reduction in the CD4⁺CXCR5⁺PD-1⁺ Tfh cell counts and its subsets, with a corresponding decrease in plasma levels of IL-6 and IL-17A (p?Conclusion: An increased number of CD4⁺CXCR5⁺PD-1⁺ Tfh cells were observed in DN patients, which may be new targets for intervention in DN.     

外周血CD4+CXCR5+滤泡辅助性T细胞与慢性乙型肝炎患者高球蛋白血症相关

目的 检测外周血CD4+ CXCR5+滤泡辅助性T细胞(Tfh细胞)的频率及其表面标志,分析与慢性乙型肝炎(乙肝)患者高球蛋白血症的关系.方法 收集健康人、乙肝患者及乙肝高球蛋白血症患者的外周血,分离血浆及外周血单个核细胞(PBMC),ELISA检测血浆中IL-21、CXCL13和IFN-γ水平,流式细胞术检测PBMC中CD4+ CXCR5+ Tfh细胞的频率及其表面PD-1、ICOS及CD40L的表达情况.结果 乙肝高球蛋白血症患者外周血CD4+ CXCR5+ Tfh细胞占CD4+T细胞的百分比(22.6±4.7)％明显高于普通慢性乙肝患者(11.9±3.9)％及健康志愿者(6.8±3.9)％,CD4+ CXCR5+ Tfh细胞上PD-1和CD40L的表达水平升高,血清IL-21及CXCL13水平升高,而IFN-γ水平降低,差异具有统计学意义(P＜0.05).结论 外周血CD4+ CX-CR5+ Tfh细胞与乙肝高球蛋白血症的发病相关.     

Tacrolimus (FK506) treatment of CD34+ hematopoietic progenitor cells promote the development of dendritic cells that drive CD4+ T cells toward Th2 responses

The macrolide lactone, tacrolimus (FK506), is utilized in bone marrow transplantation (BMT) to prevent graft-versus-host disease (GVHD). In the current study, we evaluated the ability of FK506 to modify the function of dendritic cells (DCs) derived from CD34+ hematopoietic progenitor cells (HPCs). Comparable to DCs obtained in the absence of FK506, DCs cultured in the presence of FK506 (FK-DCs) had higher expression of CD1a+ and formed a greater number of DC colonies. Despite the same expression of costimulatory molecules, FK-DCs displayed a reduced capacity to stimulate an allogeneic T cell response, and showed significantly lower interleukin (IL)-12 production. While normal DCs pulsed with the exogenous antigen, keyhole limpet hemocyanin (KLH) induced specific Th1-like interferon-gamma(IFN-gamma) producing CD4+ T cell line, FK-DCs induced Th2-like interleukin-4 (IL-4) producing CD4+ T cell line. These data demonstrate the ability of FK506 to induce Th2-promoting function in developing DCs.     

CXCR5+ CCR7- CD8 T cells are early effector memory cells that infiltrate tonsil B cell follicles

Naive and central memory CD8 T cells use CCR7 to recirculate through T cell zones of secondary lymphoid organs where they can encounter antigen. Here we describe a subset of human CD8 T cells expressing CXCR5 which enables homing in response to CXCL13 produced within B cell follicles. CXCR5+ CD8 T cells were found in tonsil B cell follicles, and isolated cells migrated towards CXCL13 in vitro. They expressed CD27, CD28, CD45RO, CD69, and were CD7low, and produced IFN-gamma and granzyme A but lacked perforin, a functional profile suggesting that these cells are early effector memory cells in the context of contemporary T cell differentiation models. Receptors important in the interaction with B cells, including CD70, OX40 and ICOS, were induced upon activation, and CXCR5+ CD8 T cells could to some extent support survival and IgG production in tonsil B cells. Furthermore, CXCR5+ CD8 T cells expressed CCR5 but no CCR7, suggesting a migration pattern distinct from that of follicular CD4 T cells. The finding that a subset of early effector memory CD8 T cells use CXCR5 to locate to B cell follicles indicates that MHC class I-restricted CD8 T cells are part of the follicular T cell population.     

Mouse CCL8, a CCR8 agonist, promotes atopic dermatitis by recruiting IL-5+ T(H)2 cells

Mouse CCL8 is a CC chemokine of the monocyte chemoattractant protein (MCP) family whose biological activity and receptor usage have remained elusive. Here we show that CCL8 is highly expressed in the skin, where it serves as an agonist for the chemokine receptor CCR8 but not for CCR2. This distinguishes CCL8 from all other MCP chemokines. CCL8 responsiveness defined a population of highly differentiated, CCR8-expressing inflammatory T helper type 2 (T(H)2) cells enriched for interleukin (IL)-5. Ccr8- and Ccl8-deficient mice had markedly less eosinophilic inflammation than wild-type or Ccr4-deficient mice in a model of chronic atopic dermatitis. Adoptive transfer studies established CCR8 as a key regulator of T(H)2 cell recruitment into allergen-inflamed skin. In humans, CCR8 expression also defined an IL-5-enriched T(H)2 cell subset. The CCL8-CCR8 chemokine axis is therefore a crucial regulator of T(H)2 cell homing that drives IL-5-mediated chronic allergic inflammation.