Are the Mast Cells Antigen Presenting Cells?

Mast cells have an important role in allergic reactions secreting histamine and other mediators of immediate hypersensitivity. In the present study we evaluated major histocompatibility complex (MHC) class II antigen expression in mast cells and their possible role in antigen presentation. In rats, 10% of mast cells isolated from the pleural cavity expressed MHC class II antigen; after incubation with gamma interferon (INF) 80% of the cells were positive. These findings suggest that mast ceils, in addition to their secretory function in allergic reactions, may also function as antigen presenting cells.     

Mecanotransduction and Endothelial Cells

1 IntroductionAtherosclerosis preferentially occurs in areas of complex blood flow where there are disturbed flow and low fluid shear stress, whereas laminar blood flow and high shear stress are atheroprotective~([1]). Reports of others and our studies suggest a steady laminar flow decreases some molecules and genes expression of vascular endothelial cells (EC) that may promote atherosclerosis, as well as it can differentially regulate production of many vasoactive factors at the level of gene…     

Neuropilin-1: The Glue between Regulatory T Cells and Dendritic Cells?

The interaction between dendritic cells and regulatory T cells is critical for the maintenance of self-tolerance. In this issue of Immunity, Sarris et al. (2008) find that Neuropilin-1 contributes to the prolonged interaction of regulatory T cells with dendritic cells.     

Cross-talk between Natural Killer Cells and Dendritic Cells in Innate and Adaptive Immunity

Effective immunity requires the coordinated activation ofboth innate and adaptive immune systems. Innate immu nity is evolutionarily older than adaptive immunity, draw ing immunologists′attention again after several decades offascination with the genera…     

From Adult Bone Marrow Cells to Other Cell Lineages: Transdifferentiation or Cells Fusion

Stemcellscanbecategorisedinto pluripotentstemcellsandmultipotentstemcells ,accordingtotheirdifferentialpotential.Generally ,onlyembryon icstemcellsareconsideredaspluripotentstemcellbecausetheycandifferentiateintoallcelllineagesofthefetus .Bycontrast ,thedifferentialpotentialofadultstemcellshastraditionallybeenthoughttobelimited .Itmeansthatadultstemcellsshouldonlybeabletodifferentiateandregenerateintothetissuesinwhichtheyreside .Butthistraditionalconceptisbe ingchallengedbyseveralrecentreports…     

Role of Natural Interferon-α Producing Cells (Plasmacytoid Dendritic Cells) in Autoimmunity

The type I interferons (IFNs) have antiviral, cytostatic and prominent immunomodulatory effects, which all are of great importance during viral infections. However, prolonged exposure of the immune system to type I IFN can break tolerance and initiate an autoimmune reaction, eventually leading to autoimmune disease. Recent observations in patients with systemic lupus erythematosus (SLE) have revealed that such individuals have endogenous IFN-α inducers, causing an ongoing IFN-α production and consequently a continuous stimulation of the immune system. These IFN-α inducers consist of small immune complexes (IC) containing DNA or RNA and act on the principal IFN-α producing cell, the natural IFN-α producing cell (NIPC), also termed the plasmacytoid dendritic cell (PDC). The NIPC/PDC is a key cell in both the innate and adaptive immune response but can also, either directly or via produced IFN-α, have a pivotal role in autoimmunity. In this review we summarize recent data concerning NIPC/PDC, including their activation, regulation, function and possible role in autoimmune diseases, especially SLE.     

Survivin Blockade Sensitizes Rhabdomyosarcoma Cells for Lysis by Fetal Acetylcholine Receptor–Redirected T Cells

Cellular immunotherapy may provide a strategy to overcome the poor prognosis of metastatic and recurrent rhabdomyosarcoma (RMS) under the current regimen of polychemotherapy. Because little is known about resistance mechanisms of RMS to cytotoxic T cells, we investigated RMS cell lines and biopsy specimens for expression and function of immune costimulatory receptors and anti-apoptotic molecules by RT-PCR, Western blot analysis, IHC, and cytotoxicity assays using siRNA or transfection-modified RMS cell lines, together with engineered RMS-directed cytotoxic T cells specific for the fetal acetylcholine receptor. We found that costimulatory CD80 and CD86 were consistently absent from all RMSs tested, whereas inducible T-cell co-stimulator ligand (ICOS-L; alias B7H2) was expressed by a subset of RMSs and was inducible by tumor necrosis factor α in two of five RMS cell lines. Anti-apoptotic survivin, along with other inhibitor of apoptosis (IAP) family members (cIAP1, cIAP2, and X-linked inhibitor of apoptosis protein), was overexpressed by RMS cell lines and biopsy specimens. Down-regulation of survivin by siRNA or pharmacologically in RMS cells increased their susceptibility toward a T-cell attack, whereas induction of ICOS-L did not. Treatment of RMS-bearing Rag^−/− mice with fetal acetylcholine receptor–specific chimeric T cells delayed xenograft growth; however, this happened without definitive tumor eradication. Combined blockade of survivin and application of chimeric T cells in vivo suppressed tumor proliferation during survivin inhibition. In conclusion, survivin blockade provides a strategy to sensitize RMS cells for T-cell–based therapy.Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue malignancy. Although the cure rates increased from 25% in 1970 to 70% in 1990, based on multimodal approaches with chemotherapy, surgery, and irradiation, no further improvement has been achieved during the past 20 years. In addition, patients with primary metastatic and recurrent disease, particularly those with alveolar RMS, have an extremely poor prognosis (<20% cure rate).^{1, 2} Therefore, new therapeutic approaches are urgently needed. Immunotherapies provide alternative approaches, the most promising of which are vaccination toward tumor antigens^{3, 4} and adoptive transfer of redirected cytotoxic T lymphocytes with engineered specificity provided by a chimeric antigen receptor (CAR).⁵Vaccination against RMS is tested in clinical trials using RMS-specific neopeptide or peptides from broadly expressed tumor antigens, such as WT1.^{3, 4} Complex vaccination protocols are required to achieve efficacy, including the use of autologous T cells, peptide-pulsed dendritic cells, and cytokines to maintain survival of RMS-specific T cells in vivo.³ A variety of factors, however, affect the vaccination efficiency, including the expression levels of major histocompatibility complex classes I and II and costimulatory and co-inhibitory molecules on tumor cells.^{6, 7, 8} The frequency of natural precursors of tumor-reactive T cells, moreover, varies widely in different patients and may be too low to achieve therapeutic efficacy.⁶An alternative strategy is the adoptive transfer of chimeric T cells that are genetically engineered with a CAR with predefined specificity. Chimeric T cells are redirected in an antibody-based, major histocompatibility complex–independent manner toward predefined cell surface targets. Because CD80 costimulation is indispensable for full T-cell activation, amplification, and long-term survival, the CD28 signaling domain was added to the CD3ζ signal in the CAR to sustain the CAR-redirected T-cell response in the long-term.^{9, 10, 11} CAR-redirected T cells are explored in clinical trials, with significant success.¹² The CAR used in the current study is directed against the fetal acetylcholine receptor (fAChR)^{13, 14, 15, 16} that is suitable for targeting RMS because it is expressed on various RMS subtypes but not on postnatal muscle or other relevant healthy tissue cells.^{15, 17}The cytolytic efficacy of adoptively transferred cytotoxic T cells can be affected by anti-apoptotic protection of the target cell; granzyme-mediated mitochondrial release of pro-apoptotic smac is blocked in some tumor cells, protecting from cell death by cytotoxic T lymphocytes.¹⁸ Similarly, overexpression of X-linked inhibitor of apoptosis protein (XIAP) can block execution of T-cell–mediated cytolysis, which can be overcome by phorbol-12-myristate-13-acetate-induced protein 1 (PMAIP1)-mediated enhancement of mitochondrial second mitochondria-derived activator of caspase release.¹⁹ Survivin, another IAP family member, stabilizes high XIAP levels in malignant cells, thereby contributing to apoptosis resistance.^{20, 21} Consistently, we observed that lysis of RMS cells by RMS-directed cytotoxic T cells was unexpectedly poor,²² suggesting that some resistance mechanisms may protect RMS cells.Herein, we report that RMS resistance to a cytolytic T-cell attack is the result of at least two mechanisms: lack of costimulatory molecules required for sustained T-cell activation and overexpression of anti-apoptotic molecules. Among these, survivin became crucial because survivin repression by siRNA or blockade by pharmacological interference substantially increased the susceptibility of RMS cells to a cytolytic T-cell attack, implying survivin as a key target to improve RMS sensitivity for adoptive immunotherapy.     

γδ T Cells but Not NK Cells Are Essential for Cell-Mediated Immunity against Plasmodium chabaudi Malaria

Blood-stage Plasmodium chabaudi infections are suppressed by antibody-mediated immunity and/or cell-mediated immunity (CMI). To determine the contributions of NK cells and γδ T cells to protective immunity, C57BL/6 (wild-type [WT]) mice and B-cell-deficient (J_H^−/−) mice were infected with P. chabaudi and depleted of NK cells or γδ T cells with monoclonal antibody. The time courses of parasitemia in NK-cell-depleted WT mice and J_H^−/− mice were similar to those of control mice, indicating that deficiencies in NK cells, NKT cells, or CD8⁺ T cells had little effect on parasitemia. In contrast, high levels of noncuring parasitemia occurred in J_H^−/− mice depleted of γδ T cells. Depletion of γδ T cells during chronic parasitemia in B-cell-deficient J_H^−/− mice resulted in an immediate and marked exacerbation of parasitemia, suggesting that γδ T cells have a direct killing effect in vivo on blood-stage parasites. Cytokine analyses revealed that levels of interleukin-10, gamma interferon (IFN-γ), and macrophage chemoattractant protein 1 (MCP-1) in the sera of γδ T-cell-depleted mice were significantly (P < 0.05) decreased compared to hamster immunoglobulin-injected controls, but these cytokine levels were similar in NK-cell-depleted mice and their controls. The time courses of parasitemia in CCR2^−/− and J_H^−/− × CCR2^−/− mice and in their controls were nearly identical, indicating that MCP-1 is not required for the control of parasitemia. Collectively, these data indicate that the suppression of acute P. chabaudi infection by CMI is γδ T cell dependent, is independent of NK cells, and may be attributed to the deficient IFN-γ response seen early in γδ T-cell-depleted mice.Malaria remains a leading cause of morbidity and mortality, annually killing about 2 million people worldwide (32, 33). Despite decades of research, malaria is a reemerging disease because of increasing drug resistance by malarial parasites and insecticide resistance by the mosquito vector. Most infected individuals do not succumb to malaria but develop clinical immunity where parasite replication is controlled to some degree by the immune system without eliciting clinical disease or sterile immunity (14, 38).Understanding the immunologic pathways leading to the control of blood-stage parasite replication is important for defining the mechanisms of disease pathogenesis and improving vaccines currently in development. The early events of the immune response depend upon activation of the innate immune system, which regulates the downstream adaptive immune response needed to control or cure (44). Natural killer (NK) and γδ T cells function early in the immune response to pathogens as components of the innate immune system. Both cell types have been proposed to play significant roles in the subsequent clearance of blood-stage malarial parasites by activating the adaptive immune system (35, 43, 44). The mechanism by which they accomplish this appears to be mediated via their secretion of gamma interferon (IFN-γ) induced by cytokines such as interleukin-12 (IL-12), tumor necrosis factor alpha (TNF-α), and IL-6 produced by other components of the innate immune system, including macrophages and dendritic cells (17, 25, 26, 37, 49).Blood-stage malaria parasites are cleared by mature isotypes of antibodies and/or by antibody-independent but T-cell-dependent mechanisms of immunity (2, 15, 22). Both responses require CD4⁺ αβ T cells; in addition, the expression of cell-mediated immunity (CMI) during both acute and chronic malaria is dependent on γδ T cells activated by CD4⁺ αβ T cells (29, 47, 49, 50). Wild-type (WT) mice depleted of γδ T cells by antibody treatment or gene knockout suppress P. chabaudi parasitemia by antibody-mediated immunity (AMI) (21, 52). Mice depleted of B cells by the same procedures also cure their acute infections in the same timeframe as intact control mice but then develop chronic low-grade parasitemia of long-lasting duration, indicating that B cells and their antibodies are needed to sterilize the infection as we originally reported (15, 48) and has since been confirmed by others (51). B-cell-deficient mice depleted of γδ T cells cannot suppress P. chabaudi parasitemia (49, 50, 52).The prominent role played by IFN-γ in immunity to malaria is generally accepted by most researchers. P. chabaudi malaria is more severe in WT mice treated with neutralizing antibody and in IFN-γ^−/− mice, as indicated by the increased magnitude and duration of parasitemia and mortality in mice deficient in IFN-γ versus intact controls (24, 39, 46). In B-cell-deficient animals, the similar neutralization of IFN-γ by treatment with anti-IFN-γ monoclonal antibody (MAb) or gene knockout of IFN-γ has an even greater effect on the time course of parasitemia, which remains at high levels and fails to cure (1, 46), indicating that IFN-γ is essential for the expression of anti-parasite CMI and contributes to AMI in this model system.The early source of IFN-γ remains controversial, with both NK cells and γδ T cells being proposed to produce this critical cytokine necessary for the activation of the adaptive immune response and the development of protective immunity (9). The results of earlier genetic studies failed to correlate susceptibility to P. chabaudi infection with NK activity (31, 44). Subsequently, Mohan et al. (25) reported that NK cell activity against tumor cell targets correlates with protection against P. chabaudi; anti-asialo GM1 polyclonal antibody depletion of NK cells results in significantly increased levels of peak parasitemia and a prolonged duration of infection compared to controls. The mode of action by which NK cells function appears to be via the secretion of cytokines (25) rather than direct cytotoxicity against the blood-stage parasites. The surface expression of lysosome-associated membrane protein 1 (LAMP-1) by subsets of human NK cells exposed to Plasmodium falciparum-infected erythrocytes may suggest otherwise (20). NK cells in collaboration with dendritic cells are responsible for optimal IFN-γ production dependent upon IL-12 (17, 36, 39, 40). In contrast to the findings of Mohan et al., other studies indicate similar P. chabaudi parasitemia in depleted mice and intact controls after NK1.1 MAb depletion of NK cells (19, 41, 53). Using microarray analysis of blood cells from P. chabaudi-infected mice, Kim et al. (18) reported a rapid production of IFN-γ and activation of IFN-γ-mediated signaling pathways as early as 8 h after infection; however, NK cells did not express IFN-γ or exhibit IFN-γ-mediated pathways in their analysis. At this time, NK cells are replicating and migrating from the spleen to the blood. In humans with P. falciparum malaria, increased production of IFN-γ by PBMC in response to parasitized RBCs correlates with protection from high-density parasitemia and clinical malaria (10, 11); early IFN-γ production by PBMC obtained from malaria naive donors is primarily by γδ T cells and not by NK cells (26). Animal models by definition do not exactly mimic the human condition, and the experimental malaria in mice uses distinct species from those that infect humans. Nevertheless, analysis of protective immunity provides important information on how a protective immune response to Plasmodium may be elicited.Whether both NK cells and γδ T cells have essential roles during the early stages of the immune response to blood-stage malaria remains to be determined. Likewise, whether these cells function early in CMI to malaria parasites is unknown. To address these issues, we infected NK-cell- or γδ-T-cell-depleted J_H^−/− mice with blood-stage P. chabaudi. The resulting time course of parasitemia was monitored and compared to control mice. In addition, spleen cells from depleted and control mice were profiled by cytofluorimetry, and the serum levels of inflammatory cytokines were measured.     

Interferon-γ Expression in Natural Killer Cells and Natural Killer T Cells Is Suppressed in Early Pregnancy

Recent study has suggested that innate immune system might play an important role in pregnancy progression. In this study, to investigate whether NK cells and NKT cells, instead of T cells, are the dominant populations of peripheral blood in early pregnancy, flow cytometry was used to detect the percentage and intracellular cytokine expressions of T cells, NK cells, NKT cdls in peripheral blood of non-pregnant women and early pregnant women. In our result, the percentages of NK calls and NKT calls were significantly increased in pregnancy compared to non-pregnancy. However, the percentage of T cells was not changed. We did not detect the Th2-dominance of total lymphocytes or T cells in peripheral blood of early pregnant women and there were also no significant changes of type 1 and type 2 cytokines in T cells, but IFN-γ production in both NK and NKT cells was decreased in early pregnancy. These results suggest that the innate immune system including NK cells and NKT cells should play a pivotal role in pregnancy progression. Type 1/type 2 shift mechanisms in innate immune system during the human early pregnancy should be paid more attention.     

Application of Stem Cells in Tissue Engineering

Stem cells have become an important source of seed cells for tissue engineering because they are relatively easy to expand in vitro and can be induced to differentiate into various cell types in vitro or in vivo. In the current stage, most stem cell researches focus on in vitro studies, including in vitro induction and phenotype characterization. Our center has made a great deal of effort in the in vivo study by using stem cells as seed cells for tissue construction. We have used bone marrow s…     

Self-Reactive CD4+ T Cells and B Cells in the Blood in Health and Autoimmune Disease: Increased Frequency of Thyroglobulin-Reactive Cells in Graves’ Disease

The mechanisms underlying activation of potentially self-reactive circulating B cells and T cells remain unclear. We measured the uptake of a self-antigen, thyroglobulin, by antigen presenting cells, and the subsequent proliferation of CD4⁺ T cells and B cells from healthy controls and patients with autoimmune thyroiditis. In Hashimoto's thyroiditis, B cells bound increased amounts of thyroglobulin in a complement- and autoantibody-dependent manner, and the thyroglobulin-elicited proliferation of CD4⁺ T cells and B cells was complement dependent. Increased proportions of Tg-responsive CD4⁺ T cells and B cells were found in patients with Graves’ disease. Notably, both patient groups and healthy controls exhibited higher proliferative responses to thyroglobulin than to a foreign recall antigen, tetanus toxoid. Our results suggest that self-tolerance can be broken by exposure of circulating lymphocytes to high local concentrations of self-antigen, and that complement plays a role in the maintenance of autoimmune processes, at least in Hashimoto's thyroiditis.     

Interleukin-15 Promotes the Commitment of Cord Blood CD34^＋ Stem Cells into NK Cells

Naturalkiller(NK)cellsweresubgroupoflymphocytes thatplayedanessentialroleinthecellularbasedimmune defenseagainstvirus infectedandtransfectedcells.His torically,inteleukin 2(IL 2)wasregardedasthenatural activatorforNKcells.Recently,itwasdiscoveredthat IL …     

How do Regulatory T Cells Work?

CD4⁺ T cells are commonly divided into regulatory T (Treg) cells and conventional T helper (Th) cells. Th cells control adaptive immunity against pathogens and cancer by activating other effector immune cells. Treg cells are defined as CD4⁺ T cells in charge of suppressing potentially deleterious activities of Th cells. This review briefly summarizes the current knowledge in the Treg field and defines some key questions that remain to be answered. Suggested functions for Treg cells include: prevention of autoimmune diseases by maintaining self-tolerance; suppression of allergy, asthma and pathogen-induced immunopathology; feto-maternal tolerance; and oral tolerance. Identification of Treg cells remains problematic, because accumulating evidence suggests that all the presently-used Treg markers (CD25, CTLA-4, GITR, LAG-3, CD127 and Foxp3) represent general T-cell activation markers, rather than being truly Treg-specific. Treg-cell activation is antigen-specific, which implies that suppressive activities of Treg cells are antigen-dependent. It has been proposed that Treg cells would be self-reactive, but extensive TCR repertoire analysis suggests that self-reactivity may be the exception rather than the rule. The classification of Treg cells as a separate lineage remains controversial because the ability to suppress is not an exclusive Treg property. Suppressive activities attributed to Treg cells may in reality, at least in some experimental settings, be exerted by conventional Th cell subsets, such as Th1, Th2, Th17 and T follicular (Tfh) cells. Recent reports have also demonstrated that Foxp3⁺ Treg cells may differentiate in vivo into conventional effector Th cells, with or without concomitant downregulation of Foxp3.     

Suitability of Human Tenon’s Fibroblasts as Feeder Cells for Culturing Human Limbal Epithelial Stem Cells

Corneal epithelial regeneration through ex vivo expansion of limbal stem cells (LSCs) on 3T3-J2 fibroblasts has revealed some limitations mainly due to the corneal microenvironment not being properly replicated, thus affecting long term results. Insights into the feeder cells that are used to expand LSCs and the mechanisms underlying the effects of human feeder cells have yet to be fully elucidated. We recently developed a standardized methodology to expand human Tenon’s fibroblasts (TFs). Here we aimed to investigate whether TFs can be employed as feeder cells for LSCs, characterizing the phenotype of the co-cultures and assessing what human soluble factors are secreted. The hypothesis that TFs could be employed as alternative human feeder layer has not been explored yet. LSCs were isolated from superior limbus biopsies, co-cultured on TFs, 3T3-J2 or dermal fibroblasts (DFs), then analyzed by immunofluorescence (p63α), colony-forming efficiency (CFE) assay and qPCR for a panel of putative stem cell and epithelial corneal differentiation markers (KRT3). Co-cultures supernatants were screened for a set of soluble factors. Results showed that the percentage of p63α⁺LSCs co-cultured onto TFs was significantly higher than those on DFs (p?=?0.032) and 3T3-J2 (p?=?0.047). Interestingly, LSCs co-cultures on TFs exhibited both significantly higher CFE and mRNA expression levels of ΔNp63α than on 3T3-J2 and DFs (p?<?0.0001), showing also significantly greater levels of soluble factors (IL-6, HGF, b-FGF, G-CSF, TGF-β3) than LSCs on DFs. Therefore, TFs could represent an alternative feeder layer to both 3T3-J2 and DFs, potentially providing a suitable microenvironment for LSCs culture.     

Hematopoietic Stem Cells Expansionin Rotating Wall Vessel

1 IntroductionClinical trials have demonstrated that ex vivo expanded hematopoietic stem cells (HSCs) and progenitors offer great promise in reconstituting in vivo hematopoiesis in patients who have undergone intensive chemotherapy. It is therefore necessary to develop a clinical-scale culture system to provide the expanded HSCs and progenitors. Static culture systems such as T-flasks and gas-permeable blood bags are the most widely used culture devices for expanding hematopoietic cells. Bu…     

CD4+CD7− T Cells: A Separate Subpopulation of Memory T Cells?

The CD7 molecule is apparently involved in T cell activation but is absent in a substantial subpopulation of human T cells under physiological and certain pathological conditions. The majority of CD7^– T cells expresses TCR / and is of CD4⁺ helper and CD45R0⁺CD45RA^– memory phenotype. After birth, percentages and absolute numbers of circulating CD7^– T cells increase significantly during aging. A number of molecules thought to be involved in organ-specific T cell homing are preferentially expressed within the subset of CD4⁺CD7^– T cells. Specific absence of CD7 antigen expression on T cells is observed in a variety of pathologic conditions such as cutaneous T cell lymphoma, HIV infection, rheumatoid arthritis, and kidney transplantation. Current in vitro results suggest that specific downregulation of CD7 antigen expression in T cells reflects a separate and stable differentiation state occurring late in the immune response. Expansion of CD7^– T cells in vivo has been found in certain diseases associated with chronically repeated T cell stimulation. The potential pathophysiological significance of this T cell subset in certain human diseases is discussed.