Are CD8+CD122+ cells regulatory T cells or memory T cells?

We identified CD8(+)CD122(+) regulatory T cells in the mouse. Some immunologists consider CD8(+)CD122(+) cells to be memory T cells despite our report of their regulatory function. Here, we propose a dual phenotype of these cells. Murine CD8(+)CD122(+) T cells demonstrate both memory and regulatory features in their functional profiles. Human CD8(+)CXCR3(+) T cells, which are thought to be the human counterpart of murine CD8(+)CD122(+) regulatory T cells, do not match human central memory T cells of the CD8(+)CD45RA(-)CCR7(+) phenotype. Thus, we must consider human CD8(+) regulatory T cells and murine CD8(+) regulatory T cells separately. Of human CD8(+) regulatory T cells, CD8(+)CXCR3(+) regulatory T cells can be divided into further subsets and we may be able to distinguish memory T cells and regulatory T cells. Of murine CD8(+)CD122(+) regulatory T cells, it seems to be impossible to divide CD8(+)CD122(+)CD44(+)CD62L(+) regulatory T cells into further subsets at present, indicating that this single population of cells has activities of both regulatory T cells and memory T cells.     

Increased level of both CD4+FOXP3+ regulatory T cells and CD14+HLA-DR⁻/low myeloid-derived suppressor cells and decreased level of dendritic cells in patients with multiple myeloma

Patients with multiple myeloma (MM) suffer from a general impaired immunity comprising deficiencies in humoral responses, T‐cell responses as well as dendritic cell (DC) function. Thus, to achieve control of tumour growth through immune therapy constitutes a challenge. Careful evaluation of the immune status in patients with MM seems crucial prior to active immune therapy. We evaluated the proportion of both, DC, Treg cells and myeloid‐derived suppressor cells (MDSC) in peripheral blood from patients with MM at diagnosis and in remission as well as patients with monoclonal gammopathy of undetermined significance (MGUS). We found that the proportion of both myeloid (m) DC and plasmacytoid (p) DC in patients at diagnosis was lowered compared to control donors, while only the proportion of pDC in patients in remission and with MGUS was significantly lower than in controls. The proportion of CD4+FOXP3+ Treg cells was increased in patients at diagnosis and not in patients in remission or with MGUS. Also, Treg cells from patients with MM were functionally intact as they were able to inhibit proliferation of both CD4 and CD8 T cells. Finally, we observed an increase in the proportion of CD14+HLA‐DR^?/low MDSC in patients with MM at diagnosis, illustrating that this cell fraction is also distorted in patients with MM. Taken together, our results illustrate that, both mDC, pDC, Treg cells and MDSC are affected in patients with MM underlining the fact that the immune system is dysregulated as a consequence of the disease.     

Intestinal CD103+ dendritic cells: master regulators of tolerance?

CD103(+) dendritic cells (DCs) in the intestinal mucosa play a crucial role in tolerance to commensal bacteria and food antigens. These cells originate in the lamina propria (LP) and migrate to the mesenteric lymph nodes (MLNs), where they drive the differentiation of gut-homing FoxP3(+) regulatory T cells by producing retinoic acid from dietary vitamin A. Local 'conditioning' factors in the LP might also contribute to this tolerogenic profile of CD103(+) DCs. Considerably less is understood about the generation of active immunity or inflammation in the intestinal mucosa. This might require alterations in pre-existing CD103(+) DCs, arrival of new DCs, or the action of a distinct DC population. Here, we discuss our current knowledge of this as yet incompletely understood population.     

Vγ1+ γδ T cells reduce IL-10-producing CD4+CD25+ T cells in the lung of ovalbumin-sensitized and challenged mice

In OVA-sensitized and challenged mice, gammadelta T cells expressing Vgamma1 enhance airway hyperresponsiveness (AHR) but the underlying mechanism is unclear. These cells also reduce IL-10 levels in the airways, suggesting that they might function by inhibiting CD4(+)CD25(+) regulatory T cells (T(reg)) or other CD4(+) T cells capable of producing IL-10 and suppressing AHR. Indeed, sensitization and challenge with OVA combined with inactivation of Vgamma1(+) cells increased CD4(+)CD25(+) cells in the lung, and markedly those capable of producing IL-10. The cellular change was associated with increased IL-10 and TGF-beta levels in the airways, and a decrease of IL-13. T(reg) include naturally occurring Foxp3(+) T(reg), inducible Foxp3(-) T(reg), and antigen-specific T(reg) many of which express folate receptor 4 (FR4). Although Foxp3 gene expression in the lung was also increased pulmonary CD4(+) T cells, expressing Foxp3-protein or FR4 remained stable. Therefore, the inhibition by Vgamma1(+) gammadelta T cells might not be targeting Foxp3(+) T(reg) but rather CD4(+) T cells destined to produce IL-10.     

Differential regulation of naïve and memory CD4+ T cells by alternatively activated dendritic cells

Promising immunotherapeutic tools for T cell-mediated pathologies are alternatively activated dendritic cells (aaDC), which exert their effect through the regulation and tolerization of T cells. As na?ve and memory T cells have different susceptibilities to tolerogenic signals, it is important to understand the modulatory effects of aaDC on these T cell subsets. We have examined regulation of na?ve and memory CD4+ T cells by human aaDC generated with dexamethasone, the active form of vitamin D3, 1alpha,25-dihydroxyvitamin D3, and LPS. Although aaDC induced low, primary, allogeneic responses by na?ve and memory T cells, aaDC regulated the differentiation of these T cell subsets in a distinct manner. Na?ve T cells primed by aaDC retained a strong, proliferative capacity upon restimulation but were skewed toward a low IFN-gamma/high IL-10 cytokine profile. In contrast, memory T cells primed by aaDC became hyporesponsive in terms of proliferation and cytokine production. Induction of anergy in memory T cells by aaDC was not a result of the presence of CD25hi regulatory T cells and could be partially reversed by IL-2. Both T cell subsets acquired regulatory activity and inhibited primary CD4 and CD8 responses. Addition of exogenous IL-12p70 during T cell priming by aaDC prevented anergy induction in memory T cells and cytokine polarization in na?ve T cells, indicating that the lack of IL-12p70 is a key feature of aaDC. Our finding that aaDC differentially regulate na?ve and memory T cells is important for understanding and maximizing the therapeutic potential of aaDC.     

Human mesenchymal stromal cells enhance the immunomodulatory function of CD8+CD28? regulatory T cells

One important aspect of mesenchymal stromal cells (MSCs)-mediated immunomodulation is the recruitment and induction of regulatory T (Treg) cells. However, we do not yet know whether MSCs have similar effects on the other subsets of Treg cells. Herein, we studied the effects of MSCs on CD8⁺CD28⁻ Treg cells and found that the MSCs could not only increase the proportion of CD8⁺CD28⁻ T cells, but also enhance CD8⁺CD28⁻T cells'' ability of hampering naive CD4⁺ T-cell proliferation and activation, decreasing the production of IFN-γ by activated CD4⁺ T cells and inducing the apoptosis of activated CD4⁺ T cells. Mechanistically, the MSCs affected the functions of the CD8⁺CD28⁻ T cells partially through moderate upregulating the expression of IL-10 and FasL. The MSCs had no distinct effect on the shift from CD8⁺CD28⁺ T cells to CD8⁺CD28⁻ T cells, but did increase the proportion of CD8⁺CD28⁻ T cells by reducing their rate of apoptosis. In summary, this study shows that MSCs can enhance the regulatory function of CD8⁺CD28⁻ Treg cells, shedding new light on MSCs-mediated immune regulation.     

Detection of a CD4+CD8−CD3− cell subpopulation during the differentiation of cord blood CD34+ cells into T cells in vitro

Introduction:  

Umbilical cord blood contains relatively abundant primitive CD34⁺ hematopoietic progenitor cells which can differentiate into T lymphocytes ex vivo     

The number of CD8+ T cells and NKT cells increases in the aqueous humor of patients with Behçet's uveitis

To determine whether there are differences in the immunopathogenesis of different endogenous uveitis syndromes, the phenotypic characteristics of immune cells were analysed among patients with endogenous uveitis. The aetiology of the uveitis included idiopathic recurrent acute anterior uveitis (18 patients), idiopathic intermediate uveitis (13 patients), Behçet's uveitis (17 patients), Vogt–Koyanagi–Harada syndrome (7 patients), and so on. Flow cytometric analysis was performed using immune cells of the aqueous humor and the peripheral blood during the active phase of intraocular inflammation, and monoclonal antibodies to CD3, CD4, CD8, CD14, CD19, CD56, TCR γδ, pan TCR αβ and Vα24. CD8+ T cells were predominant in the aqueous humor of the patients with Behçet's uveitis, whereas CD4+ T cells were mainly found in the aqueous humor of patients other than those with Behçet's uveitis. The number of NKT (CD3+CD56+) cells was significantly higher both in the aqueous humor and the peripheral blood of the patients with Behçet's uveitis compared with the other groups (P < 0·05). CD8+CD56+ cells were the predominant subtype of the increased NKT cells in patients with Behçet's uveitis. In addition, intraocular infiltration of CD14+ cells significantly differed among the uveitis patients (P < 0·05). These results suggest that the immunopathogenesis of endogenous uveitis can vary between syndromes, and that CD8+CD56+ NKT cells may play an important role in the immunopathogenesis of Behçet's uveitis.     

Development and evolution of RORγt+ cells in a microbe's world

The nuclear hormone receptor retinoid-related orphan receptor γt (RORγt) induces a pro-inflammatory program in lymphoid cells, culminating in the expression of interleukin-6 (IL-6), IL-17, IL-22, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor. During ontogeny, the first type of cells expressing RORγt are lymphoid tissue inducer cells, a type of innate lymphoid cell (ILC) generated in mammalian fetuses to induce the development of lymph nodes and Peyer's patches. After birth, RORγt(+) ILCs and RORγt(+) T cells are involved in the defense of epithelial surfaces against extracellular microbes and play an important role in the intestinal homeostasis with symbiotic microbiota. The development and evolution of RORγt(+) cells is intimately associated with the construction of a stable host-microbe interface.     

2-Gy whole-body irradiation significantly alters the balance of CD4+CD25? T effector cells and CD4+CD25+Foxp3+ T regulatory cells in mice

CD4⁺CD25⁺ T regulatory (Treg) cells are critical in inducing and maintaining immunological self-tolerance as well as transplant tolerance. The effect of low doses of whole-body irradiation (WBI) on CD4⁺CD25⁺Foxp3⁺ Treg cells has not been determined. The proportion, phenotypes and function of CD4⁺CD25⁺ Treg cells were investigated 0.5, 5 and 15 days after euthymic, thymectomized or allogeneic bone marrow transplanted C57BL/6 mice received 2-Gy γ-rays of WBI. The 2-Gy WBI significantly enhanced the ratios of CD4⁺CD25⁺ Treg cells and CD4⁺CD25⁺Foxp3⁺ Treg cells to CD4⁺ T cells in peripheral blood, lymph nodes, spleens and thymi of mice. The CD4⁺CD25⁺ Treg cells of the WBI-treated mice showed immunosuppressive activities on the immune response of CD4⁺CD25⁻ T effector cells to alloantigens or mitogens as efficiently as the control mice. Furthermore, 2-Gy γ-ray WBI significantly increased the percentage of CD4⁺CD25⁺Foxp3⁺ Treg cells in the periphery of either thymectomized mice or allogeneic bone marrow transplanted mice. The in vitro assay showed that ionizing irradiation induced less cell death in CD4⁺CD25⁺Foxp3⁺ Treg cells than in CD4⁺CD25⁻ T cells. Thus, a low dose of WBI could significantly enhance the level of functional CD4⁺CD25⁺Foxp3⁺ Treg cells in the periphery of naive or immunized mice. The enhanced proportion of CD4⁺CD25⁺Foxp3⁺ Treg cells in the periphery by a low dose of WBI may make hosts more susceptible to immune tolerance induction.     

Activation of cord blood myeloid dendritic cells by Trypanosoma cruzi and parasite-specific antibodies,proliferation of CD8+ T cells,and production of IFN-γ

We previously reported that Trypanosoma cruzi, the agent of Chagas disease, induces in congenitally infected fetuses a strong, adult-like parasite-specific CD8⁺ T cell response producing IFN-γ (Hermann et al. in Blood 100:2153–2158, 2002). This suggests that the parasite is able to overcome the immaturity of neonatal antigen presenting cells, an issue which has not been previously addressed. We therefore investigated in vitro the ability of T. cruzi to activate cord blood DCs and compared its effect to that on adult cells. We show that T. cruzi induces phenotypic maturation of cord blood CD11c⁺ myeloid DCs (mDCs), by enhancing surface expression of CD40, CD80, and CD83, and that parasite-specific IgG purified from cord blood of neonates born to T. cruzi-infected mothers amplify such expression. CD83, considered as the best marker of mature DCs, reaches higher level on cord blood than on adult mDCs. Allo-stimulation experiments showed that T. cruzi-activated cord blood mononuclear cells enriched in DCs (eDCs) stimulate proliferation of cord blood and adult CD3⁺ T cells to a similar extent. Of note, T. cruzi-activated eDCs from cord blood trigger more potent proliferation of CD8⁺ than CD8⁻ (mainly CD4⁺) adult T cells, a feature not observed with adult eDCs. T cell proliferation is associated with IFN-γ release and down-regulation of IL-13 production. These data show that T. cruzi potently activates human cord blood mDCs and endows eDCs to trigger CD8⁺ T cell proliferation and favor type 1 immune response. Interestingly, maternal antibodies can strengthen the development of mature DCs that might contribute to overcome the immunological immaturity associated with early life.     

Therapeutic potential of TGF-β-induced CD4+ Foxp3+ regulatory T cells in autoimmune diseases

Foxp3⁺ T regulatory cell (Treg) subsets play a crucial role in the maintenance of immune homeostasis against self-antigens. The lack or dysfunction of these cells contributes to the pathogenesis and development of many autoimmune diseases. Therefore, manipulation of these cells may provide a novel therapeutic approach to treat autoimmune diseases. In this review, we provide current opinions concerning the classification, developmental, and functional characterization of Treg subsets. Particular emphasis will be focused on the therapeutic role of TGF-β-induced CD4M⁺ Foxp3⁺ cells (iTregs) in established autoimmune disease. Moreover, the similarity and diversity of iTregs and naturally occurring, thymus-derived CD4⁺ CD25⁺ Foxp3⁺ regulatory T cells (nTregs) will be discussed, including the finding that the pro-inflammatory cytokine IL-6 can convert nTregs to IL-17-producing cells, whereas iTregs induced by TGF-β are resistant to the effects of this cytokine. Understanding these aspects may help to determine how Tregs can be used in the treatment of autoimmune diseases.     

TGF-β1 gene-modified,immature dendritic cells delay the development of inflammatory bowel disease by inducing CD4+Foxp3+ regulatory T cells

Inflammatory bowel disease (IBD) is caused by an uncontrolled immune response in the intestinal lumen, leading to inflammation in genetically predisposed individuals. Immunotherapy may be a promising approach to the treatment of IBD. Here, we show that transforming growth factor-β1 (TGF-β1) gene-modified immature dendritic cells (imDCs) could enhance the inhibitory function of imDCs and delay the progress of IBD induced by dextran sodium sulfate in mice. The results of fluorescence-activated cell sorter (FACS) demonstrated that this protective effect is mediated partially by inducing CD4⁺Foxp3⁺ regulatory T cells (Tregs) in mesentery lymph nodes to control inflammation. In vitro experiments also supported this hypothesis. In conclusion, we provide evidence that TGF-β1-modified bone marrow-derived imDCs may have a therapeutic effect to IBD.     

Swelling of rat mesangial cells induces a Ca2+-dependent Cl− conductance

Membrane voltage (V _m) and ion currents of rat mesangial cells in primary culture were measured with the patch-clamp technique in the fast whole-cell configuration.V _m was –44 ± 1 mV (_n = 138). A reduction of the osmolality from 290 to 190 mosmol/kg depolarizedV _m from –44 ± 1 to –29 ± 1 mV (_n = 118) and increased the inward and outward conductances (Gm) from 14±2 to 39 ± 4 nS and 13±2 to 37 ± 4 nS (_n = 84), respectively. During the hypotonicity-induced depolarization the cell capacitance increased significantly from 33 ± 3 to 42 ± 4 pF (_n = 40). The effect of hypotonic cell swelling onV _m was increased in a bath with a reduced extracellular Cl^– of 32 mmol/l (by 71 ± 4%,_n = 23), indicating that a Cl^– conductance was activated. The permselectivity of this conductance was I^– Br^– > Cl^–. TheV _m response was not affected in the presence of a reduced extracellular Na⁺ of 5 mmol/l (n = 13) and was inhibited in a solution with reduced extracellular Ca²⁺ concentration (by 63 ± 9%,n = 14). In microfluorescence measurements with the Ca²⁺-sensitive dye fura-2 hypotonic cell swelling induced a sustained increase of the intracellular Ca²⁺ activity, [Ca²⁺]_i (_n = 19). The increase of [Ca²⁺]_i was completely inhibited when the extracellular solution was free of Ca²⁺. TheV _m response to hypotonic cell swelling was not attenuated in the presence of the L-type Ca²⁺ channel blockers nicardipine (n = 5), nifedipine (n = 5) and verapamil (n = 5) (all at 1 mol/l). The data indicate that in rat mesangial cells, osmotic swelling induces a Ca²⁺ influx from extracellular space. This Ca²⁺ influx activates a Cl^– conductance resulting in a depolarization ofV _m. The enhanced Cl^– conductance may lead to KCl extrusion and hence regulatory volume decrease.     

Identification of the association of CD28+CD244+ Tc17/IFN-γ cells with chronic hepatitis C virus infection

CD8⁺ T cells play multiple and complex immunological roles including antiviral, regulatory, and exhaustive effects in hepatitis C virus (HCV) infected patients. Some CD8⁺ T-cell subsets were confirmed to be closely related to HCV infection such as T_CM, T_EM, T_EMRA, Tc17, and CD8⁺ Treg. Herein, we report a new subset of interleukin (IL)-17/interferon (IFN)-γ producing CD8⁺ T (Tc17/IFN-γ) cells that markedly correlate with CD28⁺CD244⁺ cells, IL-17 levels, and HCV RNA in HCV patients. During early treatment with peg-IFN-a2a plus ribavirin, the imbalance of these Tc17/IFN-γ cells could be partially restored, together with normalized serum alanine aminotransferase but not aspartate transaminase. Also, we analyzed the dynamic change of the percentage of this T cells subset in patients with different outcome after 4-week course of treatment with peg-IFN-a2a plus ribavirin and found that the percentage of CD8⁺CD28⁺CD244⁺ T cells significantly decreased in recovered patients but not in nonrecovered patients. In vitro, CD28⁺CD244⁺ T cells were the only CD8⁺ T-cell group that secreted both IL-17 and IFN-γ in this axis and blockade with anti-CD244 antibodies significantly reduced cytokine production. Taken together, this study demonstrates that the frequency and regulatory functions of CD28⁺CD244⁺ Tc17/IFN-γ cells may play an important role in persistent HCV infection.     

Differential sensitivity of naïve and subsets of memory CD4+ and CD8+ T cells to hydrogen peroxide-induced apoptosis

CD4+ and CD8+ memory T cells are identified into central and effector memory subsets, which are characterized by distinct homing patterns and functions. In this investigation, we show that na?ve and central memory CD4+ and CD8+ T cells are sensitive to hydrogen peroxide (H2O2)-induced apoptosis, whereas effector memory CD4+ and CD8+ T cells are relatively resistant to H2O2-induced apoptosis. Apoptosis in na?ve and central memory CD4+ and CD8+ is associated with the release of cytochrome c and activation of caspase-9 and caspase-3, upregulation of Bax and voltage-dependent anion channel (VDAC) expression, and decreased intracellular glutathione (GSH). In vitro GSH and a superoxide dismutase mimetic Mn(III) tetrakis (1-methyl-4-pyridyl) porphyrin inhibited H2O2-induced apoptosis in both na?ve and central memory CD4+ and CD8+ T cells. Furthermore, VDAC inhibitor 4,4'-diisothiocynostilbene-2,2'-disulfonic acid blocked H2O2-induced apoptosis. These data demonstrate that H2O2 induces apoptosis preferentially in human na?ve and central memory CD4+ and CD8+ T cells via the mitochondrial pathway by regulating intracellular GSH and the expression of Bax and VDAC.     

Lymph-borne CD8α+ dendritic cells are uniquely able to cross-prime CD8+ T cells with antigen acquired from intestinal epithelial cells

Cross-presentation of cellular antigens is crucial for priming CD8⁺ T cells, and generating immunity to intracellular pathogens—particularly viruses. It is unclear which intestinal phagocytes perform this function in vivo. To address this, we examined dendritic cells (DCs) from the intestinal lymph of IFABP-tOVA 232-4 mice, which express ovalbumin in small intestinal epithelial cells (IECs). Among lymph DCs (LDCs) only CD103⁺ CD11b⁻ CD8α⁺ DCs cross-present IEC-derived ovalbumin to CD8⁺ OT-I T cells. Similarly, in the mesenteric lymph nodes (MLNs), cross-presentation of IEC–ovalbumin was limited to the CD11c⁺ MHCII^hi CD8α⁺ migratory DCs, but absent from all other subsets, including the resident CD8α^hi DCs. Crucially, delivery of purified CD8α⁺ LDCs, but not other LDC subsets, into the MLN subcapsular lymphatic sinus induced proliferation of ovalbumin-specific, gut-tropic CD8⁺ T cells in vivo. Finally, in 232-4 mice treated with R848, CD8α⁺ LDCs were uniquely able to cross-prime interferon γ-producing CD8⁺ T cells and drive their migration to the intestine. Our results clearly demonstrate that migrating CD8α⁺ intestinal DCs are indispensable for cross-presentation of cellular antigens and, in conditions of inflammation, for the initial differentiation of effector CD8⁺ T cells. They may therefore represent an important target for the development of antiviral vaccinations.