Immunomodulation of human CD19+CD25high regulatory B cells via Th17/Foxp3 regulatory T cells and Th1/Th2 cytokines

Regulatory B (Breg) cells are a special subset of immunoregulatory cells with unique phenotypes and functions. In this study, human CD19⁺CD25^high Breg cells were purified from human peripheral blood. Based on the coculture system of Breg cells and CD4⁺ T cells in vitro, Breg cells were found to promote the increase in regulatory T (Treg) cells while decreasing the number of Th17 cells. Breg cells regulate Treg cells through two processes: cell-cell contact and cytokines. TGF-βsRII, a blocker of transforming growth factor-β (TGF-β), can attenuate the effects of Treg elevation, suggesting that TGF-β is the main cytokine, while Breg cells rather than interleukin-10 (IL-10) regulate the differentiation of Treg cells. However, Th17 cells were mainly regulated by cytokines, without an obvious regulatory effect on cell-cell contacts. Breg cells may regulate Th17 cells by a pathway independent of TGF-β and IL-6. The coculture of Breg cells and CD4⁺ T cells led to changes in the cytokine spectrum, which included significant increases in IL-4, IL-6 and IL-10 but not obvious changes in IL-2, IFN-γ and TNF. The inhibitory effect of Breg cells was weakened by blocking cell-cell contacts in cultures separated with the Transwell chamber because IL-10 decreased while IL-6 increased when compared with cocultured Breg and CD4⁺ T cells. When the IL-10 inhibitor IL-10sRα was added, IL-6 and TNF levels significantly increased, while treatment with the TGF-β inhibitor TGF-βsRII did not result in similar changes, suggesting that IL-10 is an important molecule to inhibit the proinflammatory factors IL-6 and TNF in this culture system.     

Human CD19(+)CD25(high) B regulatory cells suppress proliferation of CD4(+) T cells and enhance Foxp3 and CTLA-4 expression in T-regulatory cells

Studies in both animal models and humans have shown a subset of B cells behaving as immuno-regulatory cells, being a source of inhibitory cytokines such as IL-10 and TGF-β. Our aims were to establish the presence of human B regulatory (Breg) cells and to assess their ability to suppress proliferation of CD4(+) T cells and to mediate T regulatory (Treg) cells' properties. For this purpose, human Breg, CD4(+) T and Treg cells were purified using magnetic microbeads. CFSE-labeled CD4(+) T cells were stimulated and cultured alone or with Breg cells. Their proliferative response was determined 72 hours later based on the CFSE staining. In parallel, Treg cells were cultured alone or with Breg cells in different conditions for 24 hours, and then stained and analyzed for Foxp3 and CTLA-4 expression. We found that, the co-culture of Breg cells (defined as CD25(high) CD27(high) CD86(high) CD1d(high) IL-10(high) TGF-β(high)) with autologous stimulated CD4(+) T cells decreased significantly (in a dose-dependent way) the proliferative capacity of CD4(+) T cells. Furthermore, Foxp3 and CTLA-4 expression in Treg cells were enhanced by non-stimulated and further by ODN-CD40L stimulated Breg cells. The regulatory function of Breg cells on Treg cells was mainly dependent on a direct contact between Breg and Treg cells, but was also TGF-β but not IL-10 dependent. In conclusion, human Breg cells decrease the proliferation of CD4(+) T cells and also enhance the expression of Foxp3 and CTLA-4 in Treg cells by cell-to-cell contact.     

T follicular regulatory cells suppress Tfh-mediated B cell help and synergistically increase IL-10-producing B cells in breast carcinoma

T follicular regulatory (Tfr) cell is a recently discovered subset of T regulatory (Treg) cells. The main function of Tfr cells is thought to suppress germinal cancer reaction and inhibit B cell proliferation and Ig production. However, recent studies demonstrate that Tfr cells may be required for high-affinity Ig formation during acute virus infections. The role of Tfr cells in breast cancer is not thoroughly investigated. In this study, total circulating CD4 T cells were sorted into CD25⁺CXCR5⁻ Treg-like, CD25⁺CXCR5⁺ Tfr-like, and CD25⁻CXCR5⁺ Tfh-like subsets. Data showed that the Tfr-like subset presented intermediate levels of both Foxp3 and Bcl-6, while the Treg-like subset was high in Foxp3 and low in Bcl-6, and the Tfh-like was high in Bcl-6 and low in Foxp3. Of note, the frequencies of Tfr-like and Treg-like cells were significantly elevated in breast cancer (BC) patients than in non-cancer (NC) controls. Tfr-like cells in BC patients also expressed significantly higher levels of Foxp3 than those in NC controls. Neither Treg-like nor Tfr-like cells could support Ig production from naive B cells, while Tfh-like cells potently supported Ig production from naive B cells. Tfr-like cells increased the availability of IL-10, both by directly producing IL-10 and by increasing IL-10 production from B cells. Interestingly, Tfr-like cells increased IL-10 production from B cells synergistically with Tfh cells, but at the same time, significantly reduced Ig production in the Tfh-B cell coculture. These Tfr-mediated effects on Tfh cells were not found in canonical Treg cells. Overall, this study demonstrates several distinctive features in circulating Tfr cells and suggests that Tfr cells may promote the formation of IL-10-producing B cells in BC.

     

Regulatory B cells protect against chronic hypoxia-induced pulmonary hypertension by modulating the Tfh/Tfr immune balance

Hypoxia-induced pulmonary hypertension (HPH) is a progressive and lethal disease characterized by the uncontrolled proliferation of pulmonary artery smooth muscle cells (PASMCs) and obstructive vascular remodelling. Previous research demonstrated that Breg cells were involved in the pathogenesis of pulmonary hypertension. This work aimed to evaluate the regulatory function of Breg cells in HPH. HPH mice model were established and induced by exposing to chronic hypoxia for 21 days. Mice with HPH were treated with anti-CD22 or adoptive transferred of Breg cells. The coculture systems of Breg cells with CD4⁺ T cells and Breg cells with PASMCs in vitro were constructed. Lung pathology was evaluated by HE staining and immunofluorescence staining. The frequencies of Breg cells, Tfh cells and Tfr cells were analysed by flow cytometry. Serum IL-21 and IL-10 levels were determined by ELISA. Protein levels of Blimp-1, Bcl-6 and CTLA-4 were determined by western blot and RT-PCR. Proliferation rate of PASMCs was measured by EdU. Compared to the control group, mean PAP, RV/(LV + S) ratio, WA% and WT% were significantly increased in the model group. Anti-CD22 exacerbated abnormal hemodynamics, pulmonary vascular remodelling and right ventricle hypertrophy in HPH, which ameliorated by adoptive transfer of Breg cells into HPH mice. The proportion of Breg cells on day 7 induced by chronic hypoxia was significantly higher than control group, which significantly decreased on day 14 and day 21. The percentage of Tfh cells was significantly increased, while percentage of Tfr cells was significantly decreased in HPH than those of control group. Anti-CD22 treatment increased the percentage of Tfh cells and decreased the percentage of Tfr cells in HPH mice. However, Breg cells restrained the Tfh cells differentiation and expanded Tfr cells differentiation in vivo and in vitro. Additionally, Breg cells inhibited the proliferation of PASMCs under hypoxic condition in vitro. Collectively, these findings suggested that Breg cells may be a new therapeutic target for modulating the Tfh/Tfr immune balance in HPH.     

胎盘蛋白14增强调节性T细胞诱导滤泡调节性T细胞比例增加的作用及机制研究

目的：研究胎盘蛋白14（PP14）增强调节性T细胞（Treg细胞）诱导滤泡调节性T细胞（Tfr细胞）增殖的作用及机制。方法：分离健康志愿者外周血中的淋巴细胞；磁珠分选淋巴细胞中的Treg细胞；流式检测CD4⁺CD25⁺Foxp3⁺Treg细胞比例及其表面CTLA-4和HLA-G的表达；ELISA检测上清中IL-10和TGF-β的浓度；采用Transwell小室进行Treg细胞和淋巴细胞的共培养实验；流式检测淋巴细胞中CD4⁺CXCR5⁺Foxp3⁺Tfr细胞的比例。结果：相对于对照组，PP14组Treg细胞的比例增加了1.26倍（t=4.748，P=0.009 0），而其表面CTLA-4和HLA-G的表达与对照组没有显著的统计学差异（t=0.108，P=0.918 6；t=0.439，P=0.682 8）；ELISA的结果显示相对于对照组，PP14组Treg细胞培养上清中IL-10和TGF-β的浓度分别上升了3.66倍和3.86倍（t=6.817，P=0.002 4；t=7.537，P=0.001 7）；共培养实验显示PP14能够增强Treg细胞诱导Tfr细胞比例的增加，相对于共培养组，PP14组Tfr细胞比例增加了2.71倍（t=4.815，P=0.008 6），IL-10和TGF-β的阻断均能部分阻断这种增强作用（t=4.868，P=0.008 2；t=3.670，P=0.021 4）。结论：PP14能够通过分泌IL-10和TGF-β，显著增强Treg细胞诱导Tfr细胞比例的增加，这为不明原因复发性流产的治疗提供了一个新的靶点。     

Human retinal pigment epithelium-induced CD4CD25 regulatory T cells suppress activation of intraocular effector T cells

Murine retinal pigment epithelial (RPE) cells suppress T-cell activation by releasing soluble inhibitory factors and promote the generation of regulatory T cells in vitro. These T cells exposed to RPE supernatants (RPE-induced Treg cells) can suppress the activation of bystander effector T cells via the production of transforming growth factor-beta (TGFβ). In the present study, we showed that human RPE-induced Treg cells are also able to acquire regulatory function when human RPE cell lines were pretreated with recombinant TGFβ2. These RPE-induced Treg cells produced TGFβ1 and IL-10 but not IFNγ, and they significantly suppressed the activation of target cell lines and intraocular T-cell clones established from patients with active uveitis. Moreover, CD4⁺CD25⁺ RPE-induced Treg cells expressed CTLA-4 and Foxp3 molecules, and the CD25⁺ Treg cells profoundly suppressed the T-cell activation. Thus, in vitro manipulated Treg cells acquire functions that participate in the establishment of immune tolerance in the eye.     

TGF‐β‐producing regulatory B cells induce regulatory T cells and promote transplantation tolerance

Regulatory B (Breg) cells have been shown to play a critical role in immune homeostasis and in autoimmunity models. We have recently demonstrated that combined anti‐T cell immunoglobulin domain and mucin domain‐1 and anti‐CD45RB antibody treatment results in tolerance to full MHC‐mismatched islet allografts in mice by generating Breg cells that are necessary for tolerance. Breg cells are antigen‐specific and are capable of transferring tolerance to untreated, transplanted animals. Here, we demonstrate that adoptively transferred Breg cells require the presence of regulatory T (Treg) cells to establish tolerance, and that adoptive transfer of Breg cells increases the number of Treg cells. Interaction with Breg cells in vivo induces significantly more Foxp3 expression in CD4⁺CD25^? T cells than with naive B cells. We also show that Breg cells express the TGF‐β associated latency‐associated peptide and that Breg‐cell mediated graft prolongation post‐adoptive transfer is abrogated by neutralization of TGF‐β activity. Breg cells, like Treg cells, demonstrate preferential expression of both C‐C chemokine receptor 6 and CXCR3. Collectively, these findings suggest that in this model of antibody‐induced transplantation tolerance, Breg cells promote graft survival by promoting Treg‐cell development, possibly via TGF‐β production.     

Aging and human CD4 regulatory T cells

Alterations in immunity that occur with aging likely contribute to the development of infection, malignancy and inflammatory diseases. Naturally occurring CD4⁺ regulatory T cells (Treg) expressing high levels of CD25 and forkhead box P3 (FOXP3) are essential for regulating immune responses. Here we investigated the effect of aging on the number, phenotypes and function of CD4⁺ Treg in humans. The frequency and phenotypic characteristics of CD4⁺, FOXP3⁺ T cells as well as their capacity to suppress inflammatory cytokine production and proliferation of CD4⁺, CD25⁻ T cells (target cells) were comparable in young (age ≤40) and elderly (age ≥65) individuals. However, when CD4⁺, FOXP3⁺ Treg and CD4⁺, CD25⁻ T cells were co-cultured at a ratio of 1:1, the production of anti-inflammatory cytokine IL-10 from CD4⁺, CD25⁻ T cells was more potently suppressed in the elderly than in the young. This finding was not due to changes in CTLA-4 expression or apoptosis of CD4⁺, FOXP3⁺ Treg and CD4⁺, CD25⁻ T cells. Taken together, our observations suggest that aging may affect the capacity of CD4⁺, FOXP3⁺ T cells in regulating IL-10 production from target CD4⁺ T cells in humans although their other cellular characteristics remain unchanged.     

Role of IL‐10‐producing regulatory B cells in control of cerebral malaria in Plasmodium berghei infected mice

Cerebral malaria (CM) is a neurological syndrome often occurring in severe malaria. Although CM is known as an immunopathology in brain tissue mediated by excessive proinflammatory cytokines, the immunoregulatory mechanism is poorly understood. Here, we investigated the role of IL‐10‐producing regulatory B (Breg) cells in modulating CM development in a murine model of Plasmodium berghei ANKA infection. We observed that blood‐stage P. berghei induced expansion of IL‐10‐producing Breg cells in C57BL/6 mice. Adoptive transfer of IL‐10⁺ Breg cells to P. berghei infected mice significantly reduced the accumulation of NK and CD8⁺ T cells and hemorrhage in brain tissue, and improved the survival of the mice compared with control groups, although parasitemia levels were not altered. Treatment of Breg‐cell recipient mice with anti‐IL‐10 receptor mAb blocked the protective effect of Breg cells. Adoptive transfer of CD4⁺CD25⁺ Treg cells failed to prevent CM in infected mice. Spleen cells from Breg‐cell recipient mice produced increased levels of IL‐10 in vitro. Cell co‐culture showed that purified IL‐10⁺ B cells, but not IL‐10^? B cells, promoted IL‐10 production by CD4⁺ T cells. These results demonstrate that IL‐10‐producing Breg cells may represent an important mechanism for controlling the immunopathology and prevention of CM associated with P. berghei infection.     

Retinoic acid primes human dendritic cells to induce gut-homing,IL-10-producing regulatory T cells

The vitamin A metabolite all-trans retinoic acid (RA) is an important determinant of intestinal immunity. RA primes dendritic cells (DCs) to express CD103 and produce RA themselves, which induces the gut-homing receptors α4β7 and CCR9 on T cells and amplifies transforming growth factor (TGF)-β-mediated development of Foxp3⁺ regulatory T (Treg) cells. Here we investigated the effect of RA on human DCs and subsequent development of T cells. We report a novel role of RA in immune regulation by showing that RA-conditioned human DCs did not substantially enhance Foxp3 but induced α4β7⁺ CCR9⁺ T cells expressing high levels of interleukin (IL)-10, which were functional suppressive Treg cells. IL-10 production was dependent on DC-derived RA and was maintained when DCs were stimulated with toll-like receptor ligands. Furthermore, the presence of TGF-β during RA-DC-driven T-cell priming favored the induction of Foxp3⁺ Treg cells over IL-10⁺ Treg cells. Experiments with naive CD4⁺ T cells stimulated by anti-CD3 and anti-CD28 antibodies in the absence of DCs emphasized that RA induces IL-10 in face of inflammatory mediators. The data thus show for the first time that RA induces IL-10-producing Treg cells and postulates a novel mechanism for IL-10 in maintaining tolerance to the intestinal microbiome.     

Avian CD4CD25 regulatory T cells: Properties and therapeutic applications

Regulatory T cells (Tregs) are a subset of T cells that specialize in immune suppression. CD4⁺CD25⁺FoxP3⁺ T cells have been characterized as Tregs and extensively studied in mammals. In the absence of a putative FoxP3 ortholog in avians, CD4⁺CD25⁺ cells is characterized as Tregs in avians. Avian CD4⁺CD25⁺ cells produce high amounts of IL-10, TGF-β, CTLA-4, and LAG-3 mRNA; lack IL-2 mRNA; and suppress T cell proliferation in vitro through both contact-dependent and -independent pathways. Depleting avian CD4⁺CD25⁺ cells increases the proliferation of, IL-2 amount, and IFNγ mRNA amount of CD4⁺CD25⁻ cells. Avian CD4⁺CD25⁺ cells lose their suppressive properties immediately after inflammation and acquire supersuppressive properties once inflammation subsides. Although Treg activity could be beneficial to the host, Tregs simultaneously inhibit host immunity and cause persistent infections of certain pathogens. Therapy targeted toward alleviating Treg mediated immune suppression can improve host immunity against those persistent pathogens and benefit poultry production.     

Increased circulating follicular regulatory T cells in Hashimoto’s thyroiditis

Abstract

Objective: Follicular T helper (Tfh) cells are involved in the pathogenesis of Hashimoto's thyroiditis (HT), while follicular T regulatory (Tfr) cells inhibit Tfh cells, which mediate B cell responses. However, the role of Tfr cells in HT remains unclear.

Methods: Forty-six healthy controls (HCs) and 84 HT patients were enrolled in the study. The percentage of Treg cells, CXCR5^? Treg cells, and Tfr cells; the Tfr/Tfh ratio; and the percentage of ICOS, PD-1, CTLA-4, CXCR3 and CCR6 in Tfr cells were investigated; furthermore, the associations between the percentage of Tfr cells or the Tfr/Tfh ratio and the autoantibody indices were investigated.

Results: Compared with that in the HCs, the percentage of Treg cells in the HT patients was not significantly changed, but the percentage of CXCR5^? Tfr cells was decreased. In contrast, both the percentage of Tfr cells and the Tfr/Tfh ratio were significantly increased in the HT patients. Among the Tfr cells, the percentage of Th2-like Tfr cells was increased in the HT patients, while the percentage of Th17-like Tfr cells was decreased. Moreover, the percentages of ICOS and PD-1 on Tfr cells were significantly increased in the HT patients, while the percentage of CTLA-4 on Tfr cells was significantly decreased. However, the percentage of ICOS, PD-1 and CTLA-4 on Treg or CXCR5^? Treg cells was not significantly changed. Last, no association was found between either the percentage of Tfr cells or the Tfr/Tfh ratio and the antithyroglobulin and antithyroid peroxidase antibody levels in the HT patients.

Conclusions: In the HT patients, the circulating Tfr cell percentage and Tfr/Tfh ratio were significantly increased, but the humoral immune function of Tfr cells might be impaired.     

Follicular regulatory T cells repress cytokine production by follicular helper T cells and optimize IgG responses in mice

Follicular helper T (Tfh) cells provide crucial help to germinal center B (GCB) cells for proper antibody production, and a specialized subset of regulatory T cells, follicular regulatory T (Tfr) cells, modulate this process. However, Tfr‐cell function in the GC is not well understood. Here, we define Tfr cells as a CD4⁺ Foxp3⁺ CXCR5^hi PD‐1^hi CD25^low TIGIT^high T‐cell population. Furthermore, we have used a novel mouse model (“Bcl6FC”) to delete the Bcl6 gene in Foxp3⁺ T cells and thus specifically deplete Tfr cells. Following immunization, Bcl6FC mice develop normal Tfh‐ and GCB‐cell populations. However, Bcl6FC mice produce altered antigen‐specific antibody responses, with reduced titers of IgG and significantly increased IgA. Bcl6FC mice also developed IgG antibodies with significantly decreased avidity to antigen in an HIV‐1 gp120 “prime‐boost” vaccine model. In an autoimmune lupus model, we observed strongly elevated anti‐DNA IgA titers in Bcl6FC mice. Additionally, Tfh cells from Bcl6FC mice consistently produce higher levels of Interferon‐γ, IL‐10 and IL‐21. Loss of Tfr cells therefore leads to highly abnormal Tfh‐cell and GCB‐cell responses. Overall, our study has uncovered unique regulatory roles for Tfr cells in the GC response.     

IgM+CD27+ B cells possessed regulatory function and represented the main source of B cell-derived IL-10 in the synovial fluid of osteoarthritis patients

Synovial inflammation is observed in patients with osteoathritis (OA) and likely contributed to its exacerbation. Regulatory B (Breg) cells are shown to suppress inflammation in various diseases, including rheumatoid arthritis (RA). To examine whether Breg cells also participated in OA, we examined the synovial fluid from OA patients, and compared with that in RA patients. In OA synovial fluid, IL-10-producing B cells were present directly ex vivo and were increased upon stimulation, indicating that B cells were a source of IL-10 directly at the affected site of OA patients. Interestingly, the frequency of IL-10⁺ cells in synovial B cells was higher in OA patients than in RA patients, but the total number of IL-10⁺ B cells in OA was lower than that in RA, suggesting that OA patients presented lower B cell infiltration than RA patients. Phenotypical analysis demonstrated that the IL-10⁺ B cells were IgM⁺ and CD27⁺, but not CD24^hi or CD38^hi. To allow functional analysis of IgM⁺CD27⁺ B cells, the IgM⁺CD27⁺ B cells in the blood of OA patients were examined. These blood IgM⁺CD27⁺ B cells expressed more IL-10, but less CD80 and CD86 than non-IgM⁺CD27⁺ B cells. Blood IgM⁺CD27⁺ B cells suppressed the proliferation and IFN-γ expression of autologous T cells, and this effect could be reverted if IL-10 was inhibited. Furthermore, we found that patients with more severe OA presented lower levels of IL-10⁺ B cells in the synovial fluid. Together, our study described an IgM⁺CD27⁺ B cell subset in OA patients, which represented the major IL-10-secreting B cell type in the synovial fluid of OA patients and possessed regulatory function.     

CD27<Superscript>+</Superscript>TIM-1<Superscript>+</Superscript> memory B cells promoted the development of Foxp3<Superscript>+</Superscript> Tregs and were associated with better survival in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a rapid onset life-threatening condition involving uncontrolled propagation of inflammatory responses. Here, we observed that ARDS patients that survived presented significantly higher frequencies of TIM-1⁺ B cells, especially the CD27⁺TIM-1⁺ B cells, than the ARDS patients who succumbed to the condition. We then found that using BCR/CD40 antigen-dependent stimulation or Staphylococcus aureus Cowan (SAC) antigen-independent stimulation, TIM-1⁺ B cells presented significantly higher IL-10 secretion and/or TGF-β1 secretion, with SAC stimulation being more effective. CD4⁺ T cells that incubated with TIM-1⁺ B cells presented significantly elevated IL-10 secretion, TGF-β1 secretion, and Foxp3 expression, than CD4⁺ T cells that incubated with TIM-1^? B cells, suggesting TIM-1⁺ B cells promoted the in vitro development of Foxp3⁺ Treg cells. Interestingly, this TIM-1⁺ B cell-mediated promotion of Foxp3 expression was mostly dependent on TGF-β1 but not IL-10, since neutralization of TGF-β1, but not IL-10, resulted in the suppression of Foxp3 expression. We further showed that in TIM-1⁺ B cells, the CD27⁺ classical memory B cell subset demonstrated more regulatory potency than the CD27^? subset. Together, our results suggested that the TIM-1⁺ B cells, especially those that expressed CD27, could promote Foxp3 expression. Their clinical efficacy in treating ARDS should be examined in in vivo experiments.     

Peripheral T regulatory cells and cytokines in hepatitis E infection

This study addresses the involvement of regulatory T cells in hepatitis E (HE) infection. The study population comprised 77 acute viral HE patients, 52 recovered individuals (overall, 129 individuals with HE) and 53 healthy controls. Peripheral CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁻Foxp3⁺ frequencies by flow cytometry and HE-specific cytokines/chemokines quantitation were carried out. The median percentage of CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁻Foxp3⁺ T cells in acute patients were significantly higher compared to controls and recovered individuals. Both of the T regulatory (Treg) subset populations in overall HE were significantly elevated compared to controls. Comparisons of cytokines/chemokines revealed that the levels of IL-10 were elevated in: (a) acute viral hepatitis E (AVH-E) versus recovered individuals and controls, and (b) HE versus controls. Overall, the elevation of CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁻Foxp3⁺ frequencies and the rise in IL-10 suggest that Treg cells might be playing a pivotal role in hepatitis E virus (HEV) infection.     

Highly prevalent colorectal cancer-infiltrating LAP+ Foxp3− T cells exhibit more potent immunosuppressive activity than Foxp3+ regulatory T cells

Although elevated CD4⁺Foxp3⁺ regulatory T cell (Treg) frequencies within tumors are well documented, the functional and phenotypic characteristics of CD4⁺Foxp3⁺ and CD4⁺Foxp3⁻ T cell subsets from matched blood, healthy colon, and colorectal cancer require in-depth investigation. Flow cytometry revealed that the majority of intratumoral CD4⁺Foxp3⁺ T cells (Tregs) were Helios⁺ and expressed higher levels of cytotoxic T-lymphocyte antigen 4 (CTLA-4) and CD39 than Tregs from colon and blood. Moreover, ∼30% of intratumoral CD4⁺Foxp3⁻ T cells expressed markers associated with regulatory functions, including latency-associated peptide (LAP), lymphocyte activation gene-3 (LAG-3), and CD25. This unique population of cells produced interleukin-10 (IL-10) and transforming growth factor-β (TGF-β), and was ∼50-fold more suppressive than Foxp3⁺ Tregs. Thus, intratumoral Tregs are diverse, posing multiple obstacles to immunotherapeutic intervention in colorectal malignancies.     

CCR6− regulatory T cells blunt the restoration of gut Th17 cells along the CCR6–CCL20 axis in treated HIV-1-infected individuals

The gut CD4⁺ T cells, particularly the T helper type 17 (Th17) subset, are not completely restored in most HIV-1-infected individuals despite combined antiretroviral therapy, when initiated at the chronic phase of infection. We show here that the CCR6–CCL20 chemotactic axis is altered, with reduced CCL20 production by small intestine epithelial cells in treated HIV-1-infected individuals. This leads to impaired CCR6⁺CD4⁺ T-cell homing, particularly Th17 cells, to the small intestine mucosa. In contrast, the frequency of gut FoxP3⁺ T regulatory (Treg) cells, specifically the CCR6⁻ subset, was increased. The resulting imbalance in the Th17/CCR6⁻ Treg ratio and the associated shift from interleukin (IL)-17 to IL-10 and transforming growth factor-β (TGF-β) blunts CCL20 production by enterocytes, perpetuating a negative feedback for the recruitment of CCR6⁺CD4⁺ T cells to the small intestine in treated HIV-1-infected individuals.     

Prolonged acceptance of skin grafts induced by B cells places regulatory T cells on the histopathology scene

The participation of regulatory T (Treg) cells in B cell-induced T cell tolerance has been claimed in different models. In skin grafts, naive B cells were shown to induce graft tolerance. However, neither the contribution of Treg cells to B cell-induced skin tolerance nor their contribution to the histopathological diagnosis of graft acceptance has been addressed. Here, using male C57BL/6 naive B cells to tolerize female animals, we show that skin graft tolerance is dependent on CD25⁺ Treg cell activity and independent of B cell-derived IL-10. In fact, B cells from IL-10-deficient mice were able to induce skin graft tolerance while Treg depletion of the host inhibited 100% graft survival. We questioned how Treg cell-mediated tolerance would impact on histopathology. B cell-tolerized skin grafts showed pathological scores as high as a rejected skin from naive, non-tolerized mice due to loss of skin appendages, reduced keratinization and mononuclear cell infiltrate. However, in tolerized mice, 40% of graft infiltrating CD4⁺ cells were FoxP3⁺ Treg cells with a high Treg:Teff (effector T cell) ratio (6:1) as compared to nontolerized mice where Tregs comprise less than 8% of total infiltrating CD4 cells with a Treg:Teff ratio below 1:1. These results render Treg cells an obligatory target for histopathological studies on tissue rejection that may help to diagnose and predict the outcome of a transplanted organ.