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.     

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.     

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.     

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…     

Accumulation of Activated Invariant Natural Killer T Cells in the Tumor Microenvironment after α-Galactosylceramide-Pulsed Antigen Presenting Cells

Purpose

The intravenous administration of α-Galactosylceramide (α-GalCer)-pulsed antigen presenting cells (APCs) is well tolerated and the increased IFN-γ producing cells in the peripheral blood after the treatment appeared to be associated with prolonged survival. An exploratory study protocol was designed with the preoperative administration of α-GalCer-pulsed APCs to clarify the mechanisms of these findings, while especially focusing on the precise tumor site.

Methods

Patients with operable advanced lung cancer received an intravenous injection of α-GalCer-pulsed APCs before surgery. The resected lung and tumor infiltrating lymphocytes (TILs) as well as peripheral blood mononuclear cells were collected and the invariant NKT (iNKT) cell-specific immune responses were analyzed.

Results

Four patients completed the study protocol. We observed a significant increase in iNKT cell numbers in the TILs and augmented IFN-γ production by the α-GalCer-stimulated TILs.

Conclusion

The administration of α-GalCer-pulsed APCs successfully induced the dramatic infiltration and activation of iNKT cells in the tumor microenvironment.