CD8alpha-11b+ dendritic cells but not CD8alpha+ dendritic cells mediate cross-tolerance toward intestinal antigens

Cross-presentation is a critical process by which antigen is displayed to CD8 T cells to induce tolerance. It is believed that CD8alpha+ dendritic cells (DCs) are responsible for cross-presentation, suggesting that the CD8alpha+ DC population is capable of inducing both cross-priming and cross-tolerance to antigen. We found that cross-tolerance against intestinal soluble antigen was abrogated in C57BL/6 mice lacking mesenteric lymph nodes (MLNs) and Peyer patches (PPs), whereas mice lacking PPs alone were capable of developing CD8 T-cell tolerance. CD8alpha-CD11b+ DCs but not CD8alpha+ DCs in the MLNs present intestinal antigens to relevant CD8 T cells, while CD8alpha+ DCs but not CD8alpha-CD11b+ DCs in the spleen exclusively cross-present intravenous soluble antigen. Thus, CD8alpha-CD11b+ DCs in the MLNs play a critical role for induction of cross-tolerance to dietary proteins.     

In pregnant mice, the infection of Toxoplasma gondii causes the decrease of CD4+CD25+ -regulatory T cells

Acute maternal infection with Toxoplasma gondii during pregnancy is associated with adverse pregnancy outcomes. Although previous reports have indicated that T. gondii may result in abortion without direct transmission of the parasite to the foetus, the molecular mechanism remains unclear. CD4⁺CD25⁺-regulatory T cells are known to be involved in maternal tolerance toward the foetus-bearing alloantigens. With a model of pregnant mice infected with T. gondii , we found that Foxp3 mRNA expression levels in both splenocytes and placenta were reduced markedly during the process of infection. Furthermore, the numbers of splenic CD4⁺CD25⁺-regulatory T cells and placental Foxp3⁺ cells decreased synchronously in the infected mice, and the reduction of splenic CD4⁺CD25⁺-regulatory T cells were associated with apoptosis induced by the infection. Additionally, injection of pregnant mice with excretory–secretory antigens (ESA) of T. gondii also resulted in foetal loss, which could be partly prevented by adoptive transfer of CD4⁺CD25⁺-regulatory T cells from normal pregnant mice. These data suggest that foetal loss caused by T. gondii can be independent of vertical infection and that the decrease of CD4⁺CD25⁺-regulatory T cells during infection may represent a previously unrecognized mechanism for the pathogenesis of abortion caused by this parasite.     

Parasite stage-specific recognition of endogenous Toxoplasma gondii-derived CD8+ T cell epitopes

BACKGROUND: BALB/c mice control infection with the obligate intracellular parasite Toxoplasma gondii and develop a latent chronic infection in the brain, as do immunocompetent humans. Interferon-gamma-producing CD8+ T cells provide essential protection against T. gondii infection, but the epitopes recognized have so far remained elusive. METHODS: We employed caged major histocompatibility complex molecules to generate approximately 250 H-2L(d) tetramers and to distinguish T. gondii-specific CD8+ T cells in BALB/c mice. RESULTS: We identified 2 T. gondii-specific H-2L(d)-restricted T cell epitopes, one from dense granule protein GRA4 and the other from rhoptry protein ROP7. H-2L(d)/GRA4 reactive T cells from multiple organ sources predominated 2 weeks after infection, while the reactivity of the H-2L(d)/ROP7 T cells peaked 6-8 weeks after infection. BALB/c animals infected with T. gondii mutants defective in establishing a chronic infection showed altered levels of antigen-specific T cells, depending on the T. gondii mutant used. CONCLUSIONS: Our results shed light on the identity and the parasite stage-specificity of 2 CD8+ T cell epitopes recognized in the acute and chronic phase of infection with T. gondii.     

CD2 deficiency partially prevents small bowel inflammation and improves parasite control in murine Toxoplasma gondii infection

To investigate whether bowel inflammation and/or parasite control is altered in the absence of the T cell adhesion molecule CD2.     

Identification of both myeloid CD11c+ and lymphoid CD11c− dendritic cell subsets in cord blood

Dendritic cells (DCs) are the most potent antigen-presenting cells described to date. In human peripheral blood, both myeloid and lymphoid subsets of DCs have been identified. In contrast, cord blood (CB) DCs have recently been described as being exclusively of the immature CD11c- lymphoid DC subset. Using an alternative method of enrichment, based on a negative selection system, both lymphoid (HLA-DR+ CD123+++ CD11c- CD33-) and myeloid (HLA-DR++ CD123+ CD11c+ CD33+) DCs were identified in CB. Although the majority of CB DCs showed a lymphoid phenotype, a significant number of CD11c+ myeloid DCs (25.6% +/- 14.5%, n = 13) were also present. Other markers, such as CD80 and CD83, were negative in both subsets. Analyses of the allostimulatory capacity of both subsets showed that freshly isolated CB lymphoid DCs failed to induce a potent allostimulation of naive CB T cells. These features are therefore consistent with previous work reporting an immature phenotype for lymphoid DCs in adult blood. The significance of the inverted CD11c+/CD11c- ratio observed in CB DCs (1:3) with respect to adult blood DCs (3:1) remains to be explained.     

肠上皮内淋巴细胞抗弓形虫感染的免疫功能研究进展

刚地弓形虫(Toxoplasma gondii)经口感染后引发一系列免疫应答,包括先天性免疫和获得性免疫应答。某些近交系小鼠感染后肠道内稳态平衡的改变,导致急性回肠炎。肠道相关淋巴组织(gut-associatedlymphoid tissue,GALT)为抵抗弓形虫感染的首道屏障,肠上皮内CD4 T细胞分泌趋化因子和细胞因子来清除弓形虫,而肠上皮内CD8 T细胞分泌转化生长因子来减轻炎症反应。该文综述了经口感染弓形虫后,以肠上皮内淋巴细胞(intestinal intraepithelial lymphocytes,iIEL)为代表的GALT细胞群在抗弓形虫感染中的免疫功能特征。     

Demonstration of strain-specific CD8 T cell responses to Theileria annulata

The present study set out to examine the nature and specificity of the bovine CD8 T cell response at the clonal level in a group of eight animals immunized with a cloned population of Theileria annulata . The results demonstrated that immunized animals generated parasite-specific CD8 T cells that produced IFNγ in response to parasite stimulation but had highly variable levels of cytotoxicity for parasitized cells. The study also demonstrated that these parasite-specific CD8 T cells could be propagated and cloned in vitro from the memory T cell pool of cattle immunized with live T. annulata parasites. Within the small group of animals studied, there was evidence that responses were preferentially directed to antigens presented by an A10⁺ class I major histocompatibility complex (MHC) haplotype, suggesting that responses restricted by products of this haplotype may be dominant. The A10-restricted responses showed differential recognition of different parasite isolates and clones. By using a cloned population of parasites both for immunization of the animals and for in vitro analyses of the responses, we obtained unambiguous evidence that at least a proportion of CD8 T cells restricted by one MHC haplotype were parasite strain restricted.     

Active MAC-1 (CD11b/CD18) on DCs inhibits full T-cell activation

The beta2 integrins are important for transendothelial migration of leukocytes as well as for T-cell activation during antigen presentation. Despite abundant expression of beta2 integrins on antigen-presenting cells (APCs), their functional relevance for antigen presentation is completely unclear. We show here that dendritic cells (DCs) from CD18-deficient mice, which lack all functional beta2 integrins, have no defect in antigen presentation. Moreover, DCs from normal mice express inactive beta2 integrins that do not become activated on contact with T cells, at least in vitro. Pharmacologic activation of beta2 integrins on DCs results in a significant reduction of their T cell-activating capacity. This effect is mediated by Mac-1 (CD11b/CD18) on DCs because it could be reversed via blocking antibodies against CD18 and CD11b. Furthermore, the antigen-presenting capacity of macrophages, which express constitutively active beta2 integrins, is significantly enhanced on Mac-1 blockade. We therefore conclude that active CD11b/CD18 (Mac-1) on APCs directly inhibits T-cell activation.     

Regulatory T Cells in children with intestinal parasite infection

Chronic intestinal parasite infection can induce both persistent immune activation and defective responsiveness of T cells. This study aimed to assess the number and function of T regulatory (Treg) cells in children with intestinal parasite infection. We have studied the peripheral blood from 93 children, 53 of them parasitized with protozoa, helminths, or both; the remainder were non parasitized, healthy controls. The number and function of CD4⁺ CD25^high and CD4⁺ Foxp3⁺ cells were similar in parasitized and control children. In contrast, there was a significant increase in the levels of CD3⁺ CD69⁺, CD4⁺ CTLA-4⁺, and CD8⁺ CD28⁻ T cells in helminth infected children. Moreover, some of these patients showed a diminished response to CD3/CD28 stimulation in comparison with the control children. Our data strongly suggest that whilst Treg cells are not affected by intestinal parasite infection, CD3⁺ CD69⁺, CD4⁺ CTLA-4⁺ and CD8⁺ CD28⁻ lymphocytes may play an important, but as yet undetermined role in the diminished immune competence observed in parasitized children.     

Viral-induced encephalitis initiates distinct and functional CD103+ CD11b+ brain dendritic cell populations within the olfactory bulb

Dendritic cells (DC) are antigen-presenting cells found in both lymphoid and nonlymphoid organs, including the brain (bDC) of Cd11c/eyfp transgenic C57BL/6 mice. Using an intranasal vesicular stomatitis virus infection, we demonstrated that EYFP(+) cells amass in areas associated with viral antigens, take on an activated morphology, and project their processes into infected neuronal tissue within the olfactory bulb. These bDC separated into three EYFP(+) CD45(+) CD11b(+) populations, all but one being able to functionally promote both T lymphocyte proliferation and T(H)1 cytokine production. One population was shown to emanate from the brain and a second population was peripherally derived. The third population was of indeterminate origin, being both radiosensitive and not replenished by donor bone marrow. Finally, each EYFP(+) population contained CD11b(+) CD103(+) subpopulations and could be distinguished in terms of CD115, Gr-1, and Ly-6C expression, highlighting mucosal and monocyte-derived DC lineages.     

Identification of CD8alpha+CD11c- lineage phenotype-negative cells in the spleen as committed precursor of CD8alpha+ dendritic cells

CD8alpha+ dendritic cells (DCs) represent a functionally distinct DC subset in vivo, which plays a critical role in initiating various cellular immune responses. However, the committed precursor of CD8alpha+ DCs remains to be identified. We reported here that murine splenic CD8alpha+CD11c- lineage phenotype (Lin)- cells could differentiate into CD8alpha+ DCs in vivo after intravenous transplantation. Immunohistochemistry staining showed that donor-derived DCs mainly located in T-cell areas of the spleen. Functionally, these CD8alpha+CD11c-Lin- cell-derived DCs were capable of stimulating allogenic T-cell response, as well as secreting bioactive interleukin 12 p70 and interferon gamma. Freshly isolated CD8alpha+CD11c-Lin- cells expressed CC chemokine receptor (CCR)2, CCR5, and CCR7 messenger RNA, whereas CD8alpha+ DCs derived from CD8alpha+CD11c-Lin- cells further obtained the expression of CCR6 and macrophage-derived chemokine. Flow cytometry analysis showed that CD8alpha+CD11c-Lin- cells were identified in bone marrow and lymph nodes. Moreover, transplanted splenic CD8alpha+CD11c-Lin- cells could also home to thymus and lymph nodes and were capable of developing into CD8alpha+ DCs in these locations. However, CD8alpha+CD11c-Li- cells failed to differentiate into CD8alpha- DCs, T cells, natural killer cells, or other myeloid lineage cells in irradiated chimeras. Taken together, all these findings suggest that CD8alpha+CD11c-Lin- cells are a committed precursor of CD8alpha+ DCs.     

Characterization of peripheral blood CD8/11b cells in bone marrow transplant recipients. III. Subsets of CD8/11b cells differentially regulate immunoglobulin production.

Recovering bone marrow transplant (BMT) recipients have 20-70% circulating lymphocytes which co-express CD8 and CD11b (normals = 5-15%). These CD8/11b cells comprise at least two subpopulations distinguished by their expression of CD3. The CD3+ CD8/11b cells are T lymphocytes which exhibit in vitro suppressor activity (Ts); the CD3- CD8/11b cells express CD16 and are natural killer (NK) cells. In this study, we investigated whether such cells influenced circulating levels of IgA and IgM in 18 BMT recipients who each had greater than 30% circulating CD8/11b cells. We observed that in all patients whose CD8/11b cells were Ts lymphocytes (7/7) IgM and IgA levels were less than 10% of normal. Among those patients whose CD8/11b cells were NK cells (n = 11), two groups were distinguished. In one group (n = 5), less than 35% of patient NK cells expressed CD57 and serum levels of IgM and IgA were less than 10% of normal. In the second group (n = 6) greater than 60% of the NK cells expressed CD57 and serum levels of IgM and IgA were normal. In summary, our data indicate that BMT recipients have at least three distinct subsets of CD8/11b lymphocyte populations which may differentially regulate IgM and IgA production in vivo.     

经口灌胃感染弓形虫诱导的BALB/c小鼠肠道粘膜免疫应答

目的 研究BALB/c小鼠经口感染(灌胃)弓形虫速殖子后肠液IgA抗体分泌的动态变化及肠道粘膜组织诱导与效应部位T淋巴细胞亚群的变化,探讨肠道粘膜免疫应答机制.方法 将6～8周龄BALB/c小鼠100只随机分为对照组和感染组.感染组经口感染(灌胃)弓形虫RH株速殖子5×104个/只,对照组给予等量PBS.于感染后第2、4、6、8、10、13、16、19、22、25 d处死小鼠,每次5只.收集各时间点肠道冲洗液,用ELISA法测定肠液IgA水平;分离第2、4、6、8、10 d Peyer's Patches(PP)、肠系膜淋巴结(MLN)及小肠上皮内淋巴细胞(IEL),制备悬液并涂片,用免疫细胞化学方法测定CD4+、CD8+T细胞亚群水平.结果 在感染后第4、6、8、13 d实验组的肠液IgA抗体分泌显著高于对照组(P＜0.01).实验组PP结CD4+T细胞水平在6、8、10 d显著高于对照组(P＜0.05);CD8+T细胞水平与对照组无显著性差异,CD4+/CD8+比值在6、8、10 d显著升高(P＜0.05).肠系膜淋巴结的CD4+、CD8+及CD4+/CD8+比值各时间点均无显著变化.感染后第6、8、10 d,效应部位小肠上皮内淋巴细胞CD8+T细胞增高显著(P＜0.01)、CD4+/CD8+比值倒置(P＜0.05).结论 经口感染弓形虫BALB/c小鼠的肠道产生高水平的IgA抗体,作为局部首道屏障,发挥着重要的抗虫作用.诱导部位PP CD4+T细胞水平明显增高,诱导对弓形虫抗原的处理提呈作用;效应部位IEL CD8+T细胞亚群增殖明显,在清除虫体的过程中起主导作用.     

Antigen-induced, tolerogenic CD11c+,CD11b+ dendritic cells are abundant in Peyer's patches during the induction of oral tolerance to type II collagen and suppress experimental collagen-induced arthritis

OBJECTIVE: Although oral tolerance is a well-known phenomenon, the role of dendritic cells (DCs) is not well characterized. This study was conducted to better understand the differential role played by each Peyer's patch DC subset in the induction of oral tolerance to type II collagen (CII) in murine collagen-induced arthritis (CIA). METHODS: CII was fed 6 times to DBA/1 mice beginning 2 weeks before immunization, and the effect on arthritis was assessed. We compared the proportion of CD11c+,CD11b+ DCs and CD11c+,CD8alpha+ DCs in the Peyer's patches of CII-fed tolerized and phosphate buffered saline-fed nontolerized mice after the induction of CIA. The immunosuppressive properties of each DC subset were determined using fluorescence-activated cell sorter analysis for intracellular interleukin-10 (IL-10) and IL-12 and mixed lymphocyte culture. The ability of each DC subset to induce CD4+,CD25+ T regulatory cells was also examined. Mice were injected with CII-pulsed CD11c+,CD11b+ DCs isolated from Peyer's patches of tolerized mice, and the effect on CIA was examined. RESULTS: The severity of arthritis was significantly lower in tolerized mice. The proportion of CD11c+,CD11b+ DCs was increased in the Peyer's patches of tolerized mice and those DCs exhibited immunosuppressive characteristics, such as increased IL-10 production, inhibition of T cell proliferative responses to CII, and CD4+,CD25+ regulatory T cell induction. Furthermore, the CD11c+,CD11b+ DCs suppressed the severity of arthritis upon adoptive transfer. CONCLUSION: Our observations demonstrate that CD11c+,CD11b+ DCs, which are abundant in Peyer's patches during the induction of oral tolerance to CII, are crucial for the suppression of CIA and could be exploited for immunotherapy of autoimmune diseases.     

Role of gamma interferon and T cells in congenital Toxoplasma transmission

In the BALB/c mouse model, primary infection with Toxoplasma gondii during the second third of gestation leads to a high percentage of infected foetuses. However, immunity induced by infection contracted before pregnancy prevents parasites from crossing the placenta and completely protects the foetuses, as well as the pregnant women. In order to clarify the roles of CD4+, CD8+ T lymphocytes and IFN-gamma in this protection, pregnant BALB/c mice were treated with depleting monoclonal antibodies against CD4, CD8, IFN-gamma, or control antibody. Only the foetuses of the groups treated with anti-CD8 and anti-IFN-gamma antibodies developed congenital toxoplasmosis. The maternal production of IFN-gamma was depressed in the mice depleted of CD4 and CD8 cells (P < 0.001). Determination of the blood parasite load demonstrated that materno-foetal transmission of T. gondii correlates with maternal parasitaemia. Together, these results show that CD8+ T lymphocytes and IFN-gamma play an important role in protection against congenital toxoplasmosis during reinfection.     

Major role for CD8+ T cells in the protection against Toxoplasma gondii following dendritic cell vaccination

Toxoplasma gondii is the causative agent of toxoplasmosis, a worldwide zoonosis for which an effective vaccine is needed. Vaccination with pulsed dendritic cells is very efficient but their use in a vaccination protocol is unconceivable. Nevertheless, unravelling the induced effector mechanisms is crucial to design new vaccine strategies. We vaccinated CBA/J mice with parasite extract-pulsed dendritic cells, challenged them with T. gondii cysts and carried out in vivo depletion of CD4⁺ or CD8⁺ T lymphocytes to study the subsequent cellular immune response and protective mechanisms. CD4⁺ lymphocytes were poorly implicated either in spleen and mesenteric lymph node (MLN) cytokine secretion or in mice protection. By contrast, the increasing number of intracerebral cysts and depletion of CD8⁺ cells were strongly correlated, revealing a prominent role for CD8⁺ lymphocytes in the protection of mice. Splenic CD8⁺ lymphocytes induce a strong Th1 response controlled by a Th2 response whereas CD8⁺ cells from MLNs inhibit both Th1 and Th2 responses. CD8⁺ cells are the main effectors following dendritic cell vaccination and Toxoplasma infection while CD4⁺ T cells only play a minor role. This contrasts with T. gondii infection which elicits the generation of CD4⁺ and CD8⁺ T cells that provide protective immunity.     

Characteristics of CD11c+CD5+ chronic B-cell leukemias and the identification of novel peripheral blood B-cell subsets with chronic lymphoid leukemia immunophenotypes.

Previous studies have indicated that chronic lymphocytic leukemias (CLL) are characterized by the coexpression of CD5 and B-cell antigens, while hairy cell leukemias (HCL) typically express CD11c+CD5- B-cell immunophenotypes. In this report we describe the features of B-cell leukemias with CD11c+CD5+ immunophenotypes and the identification of novel circulating B-cell subsets defined by the expression of CD20, CD5, and CD11c antigens. Morphologic evaluation of 14CD11c+CD5+ B-cell leukemias showed that they generally had larger cellular diameters (14 to 21 microns) and lower nuclear:cytoplasm ratios than typical small lymphocyte CLL. These cases did not exhibit the well-defined nucleoli characteristic of prolymphocytic leukemia (PLL). The presenting clinical features of CD11c+CD5+ B-cell leukemias were most consistent with CLL or PLL, and none of the evaluated cases had pancytopenia, splenomegaly, and cytoplasmic villi characteristic of HCL. Examination of normal peripheral blood (n = 6) by three-color flow cytometry identified four novel B-cell subsets with the following immunophenotypes (mean percent of total CD20+ B cells +/- SE): CD20+CD5+CD11c+ (8.0 +/- 1.6); CD20+CD5-CD11c+ (12.0 +/- 2.0); CD20+CD5+CD11c- (35.0 +/- 4.9); and CD20+CD5-CD11c- (44.0 +/- 5.0). Our findings suggest that CD11c+CD5+ B-cell leukemias with atypical morphologic features represent forms of CLL or PLL rather than HCL. In addition, we have identified novel subsets of circulating B cells defined by patterns of CD20, CD5, and CD11c expression that correspond to the immunophenotypes of chronic B-cell leukemias.     

Flow cytometric analysis of membrane CD11b, CD11c and CD14 expression in acute myeloid leukaemia: relationships with monocytic subtypes and the concept of relative antigen expression.

Blast cells from 26 cases of acute myeloid leukaemia (AML) were examined, by single and "two-colour" flow cytometry, for relationships between membrane CD11b (monoclonal antibody OKM1), CD11c (KB90) and CD14 (Leu-M3). Increased expression of all three determinants was associated with myelomonocytic leukaemias, with their relative diagnostic value in discriminating monocytic (M4 and M5) from non-monocytic (M1, M2 and M3) subtypes being CD14 greater than CD11c greater than CD11b. However, the results also indicated, because of the heterogenous expression of CD11c in particular, and to a lesser extent CD11b, that the patterns or histograms of fluorescent staining were potentially more informative than an empirical subdivision of blasts into positive and negative subpopulations. In addition, analysis of phenotypic correlations by simultaneous two-colour fluorescence showed that the expression of CD11b and CD11c determinants by leukaemic myeloid blasts was highly correlated, in contrast to the expression of CD14 and CD11c which were relatively independent. Consequently, CD11c+ myeloid blasts almost always coexpressed CD11b whereas CD14+ cases of AML often comprised CD14+ CD11c+ and CD14+ CD11c- subpopulations. It is concluded from these observations that CD11c immunophenotyping is a useful supplementary investigation, particularly in CD14- cases of myelomonocytic leukaemia. However, it is also apparent that the presence of membrane CD11c per se is not lineage-specific and that the level of expression is perhaps a more discriminatory factor.     

弓形虫RH株在实验感染小鼠体内分布的研究

以间接免疫酶法观察弓形虫感染时的急性期病变特点及虫体在主体脏器的动态分布,以期为弓形虫病的病理诊断提供依据,并对弓形虫致病机理加深理解。方法用弓形虫ＲＨ株速殖子１０＾３个经腹腔感染昆明小鼠,于感染后第２、４、６和８ｄ,取肝、脾、肺和脑进行间接免疫酶染色。     

Lack of IL-15 results in the suboptimal priming of CD4+ T cell response against an intracellular parasite

IFN-gamma-producing CD4+ T cells, although important for protection against acute Toxoplasma gondii infection, can cause gut pathology, which may prove to be detrimental for host survival. Here we show that mice lacking IL-15 gene develop a down-regulated IFN-gamma-producing CD4+ T cell response against the parasite, which leads to a reduction in gut necrosis and increased level of survival against infection. Moreover, transfer of immune CD4+ T cells from WT to IL-15-/- mice reversed inhibition of gut pathology and caused mortality equivalent to levels of parental WT mice. Down-regulated CD4+ T cell response in the absence of IL-15, manifested as reduced antigen-specific proliferation, was due to defective priming of the T cell subset by dendritic cells (DCs) of these animals. When stimulated with antigen-pulsed DCs from WT mice, CD4+ T cells from IL-15-/- mice were primed optimally, and robust proliferation of these cells was observed. A defect in the DCs of knockout mice was further confirmed by their reduced ability to produce IL-12 upon stimulation with Toxoplasma lysate antigen. Addition of exogenous IL-15 to DC cultures from knockout mice led to increased IL-12 production by these cells and restored their ability to prime an optimal parasite-specific CD4+ T cell response. To our knowledge, this is the first demonstration of the role of IL-15 in the development of CD4+ T cell immunity against an intracellular pathogen. Furthermore, based on these observations, targeting of IL-15 should have a beneficial effect on individuals suffering from CD4+ T cell-mediated autoimmune diseases.