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Results for “Cellular Microenvironment”

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PubMed2023

GBMdeconvoluteR accurately infers proportions of neoplastic and immune cell populations from bulk glioblastoma transcriptomics data.

BACKGROUND: Characterizing and quantifying cell types within glioblastoma (GBM) tumors at scale will facilitate a better understanding of the association between the cellular landscape and tumor phenotypes or clinical correlates. We aimed to develop a tool that deconvolutes immune and neoplastic cells within the GBM tumor microenvironment from bulk RNA sequencing data. METHODS: We developed an IDH wild-type (IDHwt) GBM-specific single immune cell reference consisting of B cells, T-cells, NK-cells, microglia, tumor associated macrophages, monocytes, mast and DC cells. We used this alongside an existing neoplastic single cell-type reference for astrocyte-like, oligodendrocyte- and neuronal progenitor-like and mesenchymal GBM cancer cells to create both marker and gene signature matrix-based deconvolution tools. We applied single-cell resolution imaging mass cytometry (IMC) to ten IDHwt GBM samples, five paired primary and recurrent tumors, to determine which deconvolution approach performed best. RESULTS: Marker-based deconvolution using GBM-tissue specific markers was most accurate for both immune cells and cancer cells, so we packaged this approach as GBMdeconvoluteR. We applied GBMdeconvoluteR to bulk GBM RNAseq data from The Cancer Genome Atlas and recapitulated recent findings from multi-omics single cell studies with regards associations between mesenchymal GBM cancer cells and both lymphoid and myeloid cells. Furthermore, we expanded upon this to show that these associations are stronger in patients with worse prognosis. CONCLUSIONS: GBMdeconvoluteR accurately quantifies immune and neoplastic cell proportions in IDHwt GBM bulk RNA sequencing data and is accessible here: https://gbmdeconvoluter.leeds.ac.uk.

Humans↗

PubMed2001

Sarcoidosis: immunology, rheumatic involvement, and therapeutics.

Sarcoidosis is a systemic granulomatous disorder of unknown cause. It has protean manifestations and can affect any organ, including bones, joints, muscles, and vessels. This article reviews the most recent information on the immunologic and inflammatory pathogenesis of sarcoidosis and its implications for therapy. Sarcoidosis results from an overexuberant T cell-mediated immune response to the unknown antigen. This antigen presentation/T cell antigen recognition event occurs in a microenvironment that is suffused in proinflammatory cytokines and growth factors that promote cell attraction, adhesion, permeability changes, further cytokine production, and release. An amplified cellular immune response ensues, leading to granuloma formation and fibrosis. The article summarizes the new developments in the medical literature related to the rheumatologic manifestations and their detection and management in sarcoidosis patients. Osseous involvement in sarcoidosis is often underdiagnosed because it can be asymptomatic. New imaging techniques improve detection. Management of osteoporosis in sarcoidosis patients requires special attention because these patients often have an underlying disorder in calcium metabolism that results in hypercalcuria and hypercalcemia. Joint manifestations, such as the classic Lofgren syndrome with accompanying erythema nodosum, may be self-limited or may become chronic, presenting an ongoing therapeutic challenge. Sarcoidosis vasculitis can be devastating, affecting virtually any vessel in any organ and causing significant morbidity. Muscle involvement, like the bony involvement, is underdiagnosed. Symptoms of muscle weakness, aches, tenderness, and fatigue should prompt consideration of occult sarcoid myositis, often with accompanying neurogenic atrophy. Sarcoidosis treatment usually starts with a period of observation before pharmacologic intervention. Corticosteroids remain the first-line therapy. Alternatives to corticosteroids are often introduced either because of steroid intolerance or in an attempt to reduce steroid dose and side effects. The advantages and disadvantages of these second line therapies are reviewed. Medical vigilance, with attention to new patient symptoms, is important in the management of sarcoidosis, because of the tendency of this disease to present in so many and diverse patterns.

Bone Diseases↗

PubMedDate not supplied

Extracellular (36Cl) space, electrolyte, protein, and DNA content in brain of DBA and C57 mice: effects of age.

DBA/2J (DBA) mice are susceptible to audiogenic seizures (AGSs) in an age-dependent manner, susceptibility being maximal at 21 days and absent at 110 days of age. Previous studies have demonstrated that there is a decrease in anion transport and an increase in carbonic anhydrase (CA) activity in brain from DBA mice as compared with C57BL/6J (C57, non-AGS) mice at 21 days. Since these results suggest that there are alterations in cellular and electrolyte composition of brain from DBA mice, the present work was directed toward determining electrolyte content, extracellular space, and DNA content of brain from DBA and C57 mice at 21 and 110 days of age. There was a decrease in intracellular chloride and sodium content, and an increase in intracellular potassium content in cerebral cortex, cerebellum, and brainstem from DBA mice at both 21 and 110 days. Also, extracellular space was larger in these three brain tissues from DBA mice at both ages. DNA content, not different between the strains at 21 days, was significantly lower in cerebellum from DBA mice at 110 days. These findings give further evidence of alterations in the transport of ions in brain from DBA mice. In addition, they demonstrate that there are alterations in the intracellular and extracellular space values, an indication of changes in cellular composition of brain in these mice. Such changes may contribute to AGS susceptibility by disrupting the balance that normally exists in the neuronal microenvironment of the central nervous system.

Acoustic Stimulation↗

PubMed2000

Quantitative image analysis of laminin immunoreactivity in skin basement membrane irradiated with 1 GeV/nucleon iron particles.

We previously reported that laminin immunoreactivity in mouse mammary epithelium is altered shortly after whole-body irradiation with 0.8 Gy from 600 MeV/nucleon iron ions but is unaffected after exposure to sparsely ionizing radiation. This observation led us to propose that the effect could be due to protein damage from the high ionization density of the ion tracks. If so, we predicted that it would be evident soon after radiation exposure in basement membranes of other tissues and would depend on ion fluence. To test this hypothesis, we used immunofluorescence, confocal laser scanning microscopy, and image segmentation techniques to quantify changes in the basement membrane of mouse skin epidermis. At 1 h after exposure to 1 GeV/nucleon iron ions with doses from 0.03 to 1.6 Gy, neither the visual appearance nor the mean pixel intensity of laminin in the basement membrane of mouse dorsal skin epidermis was altered compared to sham-irradiated tissue. This result does not support the hypothesis that particle traversal directly affects laminin protein integrity. However, the mean pixel intensity of laminin immunoreactivity was significantly decreased in epidermal basement membrane at 48 and 96 h after exposure to 0.8 Gy 1 GeV/nucleon iron ions. We confirmed this effect with two additional antibodies raised against affinity-purified laminin 1 and the E3 fragment of the long-arm of laminin 1. In contrast, collagen type IV, another component of the basement membrane, was unaffected. Our studies demonstrate quantitatively that densely ionizing radiation elicits changes in skin microenvironments distinct from those induced by sparsely ionizing radiation. Such effects may might contribute to the carcinogenic potential of densely ionizing radiation by altering cellular signaling cascades mediated by cell-extracellular matrix interactions.

Aerospace Medicine↗

PubMed2002

Cytokines in immunity and allograft rejection.

Cytokines are highly potent regulatory molecules that are secreted by a variety of cells into the local microenvironment. These chemical messengers participate in the activation and regulation of immune function by a variety of mechanisms, including the stimulation and inhibition of cellular proliferation and differentiation. Cytokines also may have chemotactic activity. Six cytokine receptor families have been described, on the basis of their conserved structural features. Many cytokines are classified as proinflammatory cytokines, which promote both innate and adaptive immune responses. Solid-organ transplantation presents several unique challenges to the immune system, and cytokines play an important role in both antigen-dependent and antigen-independent immune recognition. The selective blockade of cytokine-mediated immune responses is a cornerstone of modern immunosuppressive therapy.

Animals↗

PubMed1990

Long-term culture of human bone marrow. I. characterization of adherent cells in flow cytometry.

Using long-term culture techniques, we were able to characterize the different adherent cell elements of the in vitro bone marrow microenvironment by flow cytometry. After 2 weeks of culture, four adherent cell subsets, L, MM, F, and M, were distinguished according to their intrinsic cellular characteristics of volume and spontaneous fluorescence. Using four immunological markers, we identified each population as a hematopoietic lymphocytic group (L), CD45+, VIM2-, CD14-; a hematopoietic myelomonocytic group (MM), CD45+, VIM2+, CD14-; a hematopoietic macrophage group (M), brightly autofluorescent, CD45+, VIM2-, CD14+; and a group of fibroblastoid cells (F) with a very high volume, CD45-, VIM2-, CD14-, and collagen III+. Isolation of the different hematopoietic and nonhematopoietic components of long-term bone marrow culture is thus possible using flow cytometry analysis according to the cell characteristic of volume and spontaneous fluorescence alone.

Antigens, CD↗

PubMed1993

A selective culture system for generating terminal deoxynucleotidyl transferase-positive lymphoid cells in vitro. III. Structure of the bone marrow microenvironment for early lymphopoiesis.

BACKGROUND: We have previously demonstrated the feasibility of generating terminal deoxynucleotidyl transferase-positive (TdT+) lymphoid precursor cells in vitro in the nonadherent compartment of a long-term xenogeneic culture system in which rat bone marrow (BM) cells are seeded onto established mouse BM adherent cell layers. We have also noted that the appearance of TdT+ cells in these cultures is preceded by the formation of clusters of lymphoblasts in close association with the mouse BM adherent cell layer. Inasmuch as the selective generation of such primitive lymphoid cells is not ordinarily observed in homogeneic (i.e., mouse: mouse, rat:rat) BM cultures, the nature of the microenvironment for the generation of committed lymphoid stem/progenitor cells has not yet been detailed. Consequently, the aim of this study was to define the cellular components in the adherent compartment of our xenogeneic culture system that are associated with the earliest stages of lymphopoiesis in vitro. EXPERIMENTAL DESIGN: The nature of the interactions between rat BM lymphoid precursor cells and mouse BM adherent microenvironmental cells was investigated by a combination of immunophenotyping and scanning and transmission electron microscopy of primary cultures. The kinetics of formation and composition of lymphoid clusters were also determined morphologically and phenotypically. Results were compared with those of other investigators who have studied lymphopoiesis in intact BM or in homogeneic cultures of pre-B cells. RESULTS: Two distinct microenvironmental regions are represented within the mouse BM adherent cell layer: (a) paucilayer (PL) regions, composed of two or three horizontally oriented layers of alkaline phosphatase-positive mouse stromal cells; and (b) multilayer (ML) regions, containing 4 to 8 layers of such stromal cells. In both regions, proliferating rat lymphoid cells, expressing the HIS24 (B220) and/or HIS50 (heat stable antigen) early B-lineage antigens, are "sandwiched" between adjacent layers of stromal cells and enveloped by cytoplasmic processes from interdigitating mouse macrophages (pseudoemperipolesis). More than 95% of the lymphoid cells are of rat origin, whereas more than 95% of the nonlymphoid cells are of mouse origin. Large clusters, containing up to 1,000 lymphoid cells, preferentially develop in the ML regions and are comprised primarily of TdT+ cells. Small clusters containing 5 to 50 lymphoid cells, preferentially develop in the PL regions and are comprised primarily of TdT- cells, that can generate TdT+ cells upon transfer onto fresh adherent cells layers. Formation of individual small clusters, which outnumber large clusters by approximately 10-fold, is initiated by as few as 25 unfractionated rat BM cells. This process is not preceded by a lag period, and is linear with respect to time and cell dose. Formation of large clusters requires approximately 30 times more input cells, and is linear with respect to time after a lag of 5 days. CONCLUSIONS: The number of small lymphoid clusters formed in vitro closely approximates the frequency of lymphoid stem/progenitor cells in the BM inoculum (3 to 5%). This suggests that, under ideal conditions, individual clusters are clonally derived and the seeding efficiency of the culture system approaches 100%. The results further suggest that large clusters are formed by the coalescence of numerous small clusters within ML regions of the adherent cell layer; and that the formation of ML regions may be supported by an underlying monolayer of macrophages. A novel aspect of this system appears to be the frequency of pseudoemperipolesis, rather than phagocytosis, of primitive lymphoid cells by macrophages, that has also been noted in vivo. Moreover, the ML regions themselves bear a close resemblance to the recently described pro-B cell-enriched, multicellular aggregate fraction of freshly harvested mouse BM. Hence, this system appears to structurally recreate in vitro the

Animals↗

PubMed1999

Altered localization of E-cadherin and alpha-catenin in rat esophageal tumors.

An alteration in the localization of E-cadherin and its associated proteins has been observed in many epithelial neoplasms. No data exist, however, for the expression of these proteins in an animal model system for esophageal cancer or in cultured rat esophageal epithelial cell lines. The present study investigated the localization of E-cadherin and its associated protein, alpha-catenin, in rat esophageal epithelial cell lines of differing tumorigenic potential; in tumors induced after transplantation of these cell lines into syngeneic hosts; and, in esophageal tumors induced in rats by the carcinogen, N-nitrosomethylbenzylamine (NMBA). Immunofluorescent staining of the cultured cell lines revealed staining for both E-cadherin and alpha-catenin at cell-cell boundaries. Western blot analysis confirmed the membrane-bound localization of E-cadherin and alpha-catenin in the cells. However, tumors induced by these cell lines in syngeneic rats showed reduction in the expression of both E-cadherin and á-catenin in the plasma membrane of invasive epithelial cells. Immunohistochemical analysis of NMBA-induced esophageal neoplasms in rats revealed E-cadherin and alpha-catenin to be abnormally expressed in poorly differentiated tumors when compared to well differentiated tumors. These results suggest that the microenvironment may have an important role in regulating the expression of these adhesion molecules in rat esophageal epithelial cells, and that alteration in the cellular localization of E-cadherin and alpha-catenin may be indicative of tumor progression in NMBA-induced rat esophageal cancer.

Animals↗

PubMed2000

Multiple Myeloma: New Insights and Therapeutic Approaches.

This review discusses the evolution of novel diagnostic and treatment strategies for multiple myeloma based upon increased understanding of basic disease pathogenesis. Although myeloma has remained an incurable illness to date, these new developments will derive treatments to improve outcome and achieve eventual cure. In Section I, Dr. Kyle reviews the results of current therapy for multiple myeloma, including high dose therapy and stem cell transplantation which have proven to achieve improved response rates, event-free, and overall survival. Supportive therapy, such as erythropoietin to treat disease-related anemia, and methods of prophylaxis against infection, which both lessen toxicities of treatment and improve quality of life for patients, are also addressed. In Section II, Dr. Dalton with Drs. Landowski, Shain, Jove and Hazlehurst discusses mechanisms of drug resistance in myeloma, with emphasis on novel treatment approaches to prevent development of drug resistance and to overcome drug resistance. Laboratory studies delineating mechanisms whereby myeloma cells resist drug-induced apoptosis provide the framework for related treatment protocols for patients with refractory disease. In Section III, Dr. Berenson reviews the management of complications in bone, which occur in the majority of patients with myeloma and are the major cause of decreased quality of life. New insights into the mediators of bone resorption and new bone formation in the marrow milieu have already derived effective bisphosphonate therapy. These drugs not only reduce bone complications and related pain, thereby improving quality of life, but also may have intrinsic anti-tumor activity by virtue of inducing tumor cell adherence to marrow, reducing interleukin-6 secretion, inducing tumor cell apoptosis, or inhibiting angiogenesis. In the last section, Dr. Anderson explores the potential for future therapies which offer great promise to improve patient outcomes. First, drugs which alter the marrow microenvironment include thalidomide and its derivative immunomodulatory drugs, which act directly on tumor cells to induce apoptosis or G1 growth arrest, alter tumor cell adhesion to marrow stroma, inhibit angiogenesis, and trigger a cellular anti-tumor response. The proteasome inhibitors both act directly on tumor cells and also inhibit the transcription factor NFkappaB-dependent upregulation of IL-6 secretion triggered by tumor cell adhesion. Second, delineation of both growth and apoptotic pathways has derived novel treatment strategies. Third, the preclinical basis and early clinical trial results using vaccination and adoptive immunotherapy to harness autoimmune and alloimmune anti-myeloma responses are presented. This review sets the stage for an evolving new biologically based treatment paradigm in myeloma targeting both the tumor and its microenvironment to improve outcome and achieve eventual cure.

Journal Article↗

PubMed1995

The extracellular matrix of the hematopoietic microenvironment.

The bone marrow microenvironment plays an important role in promoting hematopoietic progenitor cell proliferation and differentiation and the controlled egress of these developing hematopoietic cells. The establishment of long-term bone marrow cultures, which are thought to mimic hematopoiesis in vitro, and various stromal cell lines has greatly facilitated the analysis of the functions of this microenvironment. Extracellular matrix (ECM) molecules of all three categories (collagens, proteoglycans and glycoproteins) have been identified as part of this microenvironment and have been shown to be involved in different biological functions such as cell adhesion and anti-adhesion, binding and presentation of various cytokines and regulation of cell growth. It is suggested that these matrix molecules in combination with cytokines are crucial for compartmentalization of the bone marrow. Although many cell adhesion molecules have been characterized on the surface of hematopoietic progenitor cells, the nature of cellular receptors for the ECM components is less well defined. During leukemia, many immature blood cells are released from bone marrow, but it is not yet known whether these abnormalities in hematopoiesis are also caused by an altered microenvironment or altered composition of its extracellular matrix. The elucidation of the involvement of specific ECM-isoforms and as yet not characterized ECM components and their receptors in the bone marrow will certainly help towards a better understanding of these phenomena.

Animals↗

PubMed2006

Occurrence of thymosin beta4 in human breast cancer cells and in other cell types of the tumor microenvironment.

Previous studies have shown that the G-actin sequestering polypeptide thymosin beta4 frequently is overexpressed in cancers and that such overexpression correlates to malignant progression. However, the localization of thymosin beta4 in human cancers has not been determined. We now demonstrate that there is a considerable heterogeneity in the cellular distribution of thymosin beta4 in breast cancer. In most tumors examined, cancer cells showed low or intermediate reactivity for thymosin beta4, whereas leukocytes and macrophages showed intense reactivity. In addition, endothelial cells showed variable reactivity to thymosin beta4, whereas myofibroblasts were negative. There was no correlation between the intensity of tumor cell staining and histological grade, whereas there was a tendency toward a correlation between endothelial cell staining and grade. These results demonstrate that multiple cell types within the tumor microenvironment produce thymosin beta4 and that such expression varies from tumor to tumor. Such heterogeneity of expression should be taken into account when the role of thymosin beta4 in tumor biology is assessed.

Breast Neoplasms↗

PubMed1995

Myelopoiesis in the thymus of the sea bass, Dicentrarchus labrax L. (teleost).

BACKGROUND: In vertebrates the thymus is primarily regarded as a lymphoid organ whose importance lies in its capacity to produce a large number of lymphocytes that enter the circulation as T cells. In higher vertebrates the organ has also been regarded as a site for myelopoiesis, but this capacity has not been observed in fish. In this study we describe morphologically the presence of intrathymic developing myeloid cells in the sea bass. METHODS: The thymus samples were morphologically studied by transmission electron microscopy. RESULTS: We describe the coexistence of cells in different stages of erythropoiesis and granulopoiesis that appear to be developing in situ in some thymus lobes. Degenerated thymocytes and epithelial-reticular cells occur simultaneously in the same areas. CONCLUSIONS: The coexistence of different cellular components of erythropoiesis and the heterophilic series of granulopoiesis with areas of necrosis suggests a relationship between both processes that is influenced by the microenvironment. Our observations also suggest that the presence of intrathymic developing myeloid cells may imply a nonimmunological role for the thymus.

Animals↗

PubMed1990

The significance of biological heterogeneity.

Heterogeneity of expression for a variety of characteristics is found among malignant cells in the organism and in culture. Normal cells are relatively uniform when organized in a tissue, but become heterogeneous for many characteristics when they are dispersed and grown in monolayer culture. The heterogenizing effect of growth in culture indicates that the morphology and behavior of normal cells is ordered by their topological relations in tissues and other homeostatic influences of the organism. Weakening of these ordering relations may contribute to malignant transformation, as it usually does in rodent cell culture. Although phenotypic differences among cells of a given type may be transient, they can be perpetuated by protracted exposure to selective conditions. Examples are cited of selection which leads to an adapted state that is heritable for many cell generations after removal of the selective conditions. Such heritable adaptations are analogous to the Dauermodifikationen, or lingering changes, first described in ciliated protozoa and shown there to be under cytoplasmic control. The concept of progressive state selection is introduced to account for heritable adaptation at the cellular level. It depends on the spontaneous occurrence of transient, variant states and their successive selection to progressively higher levels of adaptation to an altered microenvironment. Although the process is basically epigenetic, it may be stabilized by genetic change. The concept is consistent with our present knowledge of tumor development, including progression to metastasis, and with epigenetic aspects of normal development.

Animals↗

PubMed2000

COX-2, NO, and cartilage damage and repair.

The production of nitric oxide (NO) and prostaglandin E2 (PGE(2)) is increased in human osteoarthritis-affected cartilage. These and other inflammatory mediators are spontaneously released by OA cartilage explants ex vivo. The excessive production of nitric oxide inhibits matrix synthesis, and promotes its degradation. Furthermore, by reacting with oxidants such as superoxide anion, nitric oxide promotes cellular injury, and renders the chondrocyte susceptible to cytokine-induced apoptosis. PGE(2) exerts both anabolic and catabolic effects on chondrocytes, depending on the microenvironment and physiological condition. Thus, NO and PGE(2), produced by activated chondrocytes in diseased cartilage, may modulate disease rogression in osteoarthritis, and should therefore be considered potential targets for therapeutic intervention

Cartilage, Articular↗

PubMed2000

Cytokine-secreting tumor cell vaccines.

Modification of the tumor microenvironment with gene transfer techniques stimulates two immune mechanisms that effectuate tumor destruction. One involves improved tumor-antigen presentation for the development of specific cellular and humoral immunity. The second involves compromise of the tumor vasculature by soluble factors and leukocytes.

Animals↗

PubMed1995

Cytokines increase human hemopoietic cell adhesiveness by activation of very late antigen (VLA)-4 and VLA-5 integrins.

Cytokines are known to be important regulators of normal hemopoiesis, acting in concert with components of the bone marrow microenvironment. Interactions with this microenvironment are known to regulate the proliferation, differentiation, and homing of hemopoietic progenitor (CD34+) cells. Adhesive interactions with the extracellular matrix retain CD34+ cells in close proximity to cytokines, but may also provide important costimulatory signals. Thus, the functional states of adhesion receptors are critical properties of CD34+ cells, but the physiological mechanisms responsible for regulating functional properties of cell adhesion receptors on primitive hemopoietic cells are still unknown. We confirm that the integrins very late antigen (VLA)-4 and VLA-5 are expressed on the CD34+ cell lines MO7e, TF1, and on normal bone marrow CD34+ progenitor cells, but in a low affinity state, conferring on them a weak adhesive phenotype on fibronectin (Fn). Herein, we show that the cytokines interleukin (IL)-3, granulocyte-macrophage CSF (GM-CSF), and KIT ligand (KL) are physiological activators of VLA-4 and VLA-5 expressed by MO7e, TF1, and normal bone marrow CD34+ progenitor cells. Cytokine-stimulated adhesion on Fn is dose dependent and transient, reaching a maximum between 15 and 30 min and returning to basal levels after 2 h. This cytokine-dependent activation is specific for VLA-4 and VLA-5, since activation of other beta 1 integrins was not observed. The addition of second messenger antagonists staurosporine and W7 abolished all cytokine-stimulated adhesion to Fn. In contrast, genistein inhibited KL-stimulated adhesion, but failed to inhibit GM-CSF- and IL-3-stimulated adhesion. Our data suggest that cytokines GM-CSF and IL-3 specifically stimulate beta 1 integrin function via an "inside-out" mechanism involving protein kinase activity, while KL stimulates integrin activity through a similar, but initially distinct, pathway via the KIT tyrosine-kinase. Thus, in addition to promoting the survival, proliferation, and development of hemopoietic progenitors, cytokines also regulate adhesive interactions between progenitor cells and the bone marrow microenvironment by modifying the functional states of specific integrins. These data are of importance in understanding the fundamental processes of beta 1 integrin activation and cellular response to mitogenic cytokines as well as on the clinical setting where cytokines induce therapeutic mobilization of hematopoietic progenitors.

Adult↗

PubMed2005

Autoreactivity to self H-2Kb peptides in TAP1 mice. Intravenous administration of H-2Kb class I-derived peptides induces long-term survival of grafts from C57BL/6 donors.

We and others have previously shown that TAP1-/- mice (H-2b) reject grafts from donors without major histocompatibility complex (MHC) disparity that express wild-type levels of H-2b class I molecules (C57BL/6, TAP1+/+ mice). In this same model, we also showed that subcutaneous priming of TAP1-/- mice with synthetic peptides derived from the H-2Kb molecule accelerated graft rejection and that in vivo depletion of CD4+ T cells induced a significant prolongation of graft survival, suggesting an important role for CD4 T cells. We hypothesize that, in this model, rejection is triggered by the recognition of class I molecules or derived peptides, in an inflammatory microenvironment, by a functionally altered autoreactive T-cell repertoire that escapes the control of peripheral regulatory mechanisms. In the present study, we analysed the cellular autoreactivity induced by synthetic peptides derived from the H-2Kb sequence in naive and TAP1-/- mice transplanted with C57BL/6 grafts, and investigated whether intravenous modulation of autoreactivity to these peptides induced transplantation tolerance. We showed that TAP1-/- mice have peripheral autoreactive T cells that recognize H-2Kb peptides. A significant amplification of proliferation against these peptides was detected in TAP1-/- mice that rejected grafts, indicating that the inflammatory context of transplantation induced peripheral expansion of these autoreactive T cells. Furthermore, intravenous injection of H-2Kb-derived peptides significantly prolonged graft survival in some animals. In these mice (> 100 days graft survival), we observed intragraft inhibition of interferon-gamma and interleukin-10 expression, suggesting that these cytokines have an active role during the rejection. In conclusion, our present data indicate that inflammatory autoreactive T cells directed against H-2Kb peptides can be inhibited in the periphery to prolong graft survival in TAP1-/- mice.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2006

Building signaling complexes at the membrane.

Cell membranes, the plasma membrane in particular, serve as the hub of various cellular signaling networks. In response to receptor activation, many cytosolic proteins are reversibly recruited to membranes to form dynamic signaling complexes. Membranes provide a unique microenvironment in which the formation of signaling complexes can be exquisitely modulated by the fine interplay between protein-protein and lipid-protein interactions.

Adaptor Proteins, Signal Transducing↗