In Vivo Anergized T Cells Form Altered Immunological Synapses In Vitro

T cells contact allogeneic antigen presenting cells (APCs) and assemble, at their contact interface, a molecular platform called the immunological synapse. Synapse-based molecules provide directional signals for the T cell--either positive signals, resulting in T-cell activation, or negative signals causing T-cell inactivation or anergy. To better understand the molecular basis of in vivo T-cell anergy we analyzed the contacts made between in vivo anergized T cells and APCs, and determined which signaling molecules were included or excluded from their immunological synapses. Anergy was induced in TCR transgenic mice by the intravenous injection of semiallogeneic donor spleen cells. T cells from anergized mice were mixed with APCs, the T-cell/APC synapses imaged using deconvolution microscopy, and their molecular compositions were determined. T cells from anergic mice formed unstable immunological synapses in vitro with allogeneic APCs and failed to recruit the signaling proteins necessary to initiate T-cell activation. These findings suggest that T-cell anergy induced by exposure to semiallogeneic donor cells is associated with defects in the earliest events of T-cell activation, immunological synapse formation and recruitment of TCR-mediated signaling proteins.     

Role of Integrin CD103 in Promoting Destruction of Renal Allografts by CD8+ T Cells

Infiltration of CD8(+)TCRalphabeta(+) T-effector populations (CD8 effectors) into graft epithelial compartments has long been recognized as a key lesion in progression of clinical renal allograft rejection. While the afferent phase of allograft immunity is increasingly well-defined, the efferent pathways by which donor-reactive CD8-effector populations access and ultimately destroy the graft renal tubules (rejection per se) have received remarkably little attention. This is an important gap in our knowledge of transplantation immunology, because epithelial compartments comprise the functional elements of most commonly transplanted organs including not only kidney, but also liver, lung, pancreas, and intestine. Furthermore, there is increasing evidence that attack of graft epithelial elements by CD8-effector populations not only causes short-term graft dysfunction but is also a major contributor to development of chronic allograft nephropathy and late graft loss, which now represent the salient clinical problems. Recent studies of the T-cell integrin, alpha(E)beta(7) (CD103), have provided insight into the mechanisms that promote interaction of CD8 effectors with graft epithelial compartments. The purpose of this communication is to review the known properties of the CD103 molecule and its postulated role in the efferent phase of renal allograft rejection.     

Oral administration of an edible-mushroom-derived protein inhibits the development of food-allergic reactions in mice

BACKGROUND: Food allergy is a common disease without effective treatment. Since strict elimination of food allergens may be difficult, strategies for effective intervention are urgently needed. OBJECTIVE: The aim was to investigate the prophylactic use of orally administrated FIP-fve, an immunomodulatory protein isolated from the edible mushroom Flammulina velutipes, in a murine model of food allergy. METHODS: BALB/c mice were immunized twice intraperitoneally with ovalbumin (OVA), at an interval of 2 weeks. Before and during each period of immunization, FIP-fve (200 microg per mouse) or phosphate-buffered saline was given orally every other day with a total of five doses. Then OVA-specific antibodies and cytokine profiles were determined. Subsequently, the mice were orally challenged with OVA. Symptoms of anaphylaxis, levels of plasma histamine, and histology of intestines were examined. RESULTS: Mice receiving oral FIP-fve treatment during sensitization to OVA had an impaired OVA-specific IgE response with a Th1-predominant cytokine profile. These mice were protected from systemic anaphylaxis-like symptoms induced by subsequent oral challenge with OVA. CONCLUSION: Oral administration of FIP-fve has a Th1-skewing effect on the development of the allergen-specific immune response, and may serve the purpose of immunoprophylaxis for food allergy and other allergic diseases.     

Differential Expression of Subspecies of Polyomavirus and Murine Leukemia Virus Enhancer Core Binding Protein, PEBP2, in Various Hematopoietic Cells

The core sequence of the enhancer of murine leukemia virus (MuLV) long terminal repeat is highly conserved in a large number of MuLV strains and appears to play an essential role when SL3-3 or Moloney strains induce T cell lymphoma in mice. We found by using the electrophoretic mobility shift assay that a polyomavirus enhancer core-binding protein, PEBP2, bound to this core motif of MuLV. We also noted that PEBP2 in several hematopoietic cell lines derived from B lymphocyte, macrophage and myelocyte lineages migrated significantly faster than the authentic PEBP2 detected in NIH3T3 (ibroblasts. Interestingly, PEBP2 detected in the cell lines of T lymphocyte lineage appeared to contain both types, which were indistinguishable in electrophoretic mobility from those of NIH3T3 and of B lymphocyte, macrophage and myelocyte lineages. The treatment of the nuclear extract containing PEBP2 with phosphatase generated PEBP3, which is a subcomponent of PEBP2 and retained the same DNA-binding specificity as PEBP2. The altered mobility of hematopoietic cell-derived or T lymphocyte-derived PEBP2 was found to be due to the alteration of the mobility of PEBP3. Based on the distinct mobility of PEBP2/3 of T lymphocytes from those of other hematopoietic cells, we discuss the implication of PEBP2 in MuLV-induced T cell leukemia and T cell-specific gene expression.     

Ca2+ mobilization in physiologically stimulated single T cells gradually increases with peptide concentration (analog signaling)

We have investigated Ca²⁺ mobilization in single T cells stimulated with their physiological ligand, i.e. antigenic peptide bound to major histocompatibility complex (MHC) molecules on antigen-presenting cells (APC). Fibroblasts expressing I-E^d class II molecules were pulsed with a peptide derived from the λ2³¹⁵ immunoglobulin light chain. Onto such antigen-pulsed fibroblasts were sedimented cloned Th1 cells loaded with Fura-2. Changes in cytosolic Ca²⁺ concentration in single T cells were continually monitored by use of an imaging system based on fluorometry. Ca²⁺ mobilization was both peptide-specific and MHC-restricted. Within seconds of the initial APC-T cell contact, a Ca²⁺ spike could be observed. The Ca²⁺ response gradually declined over a 25-min period, during which oscillations were noted. Various parameters characterizing the magnitude of the Ca²⁺ response (latency, increase rate, max and mean Ca²⁺ increase, frequency and period of oscillations) all correlated with the amount of peptide used for pulsing the fibroblasts. Thus, Ca²⁺ mobilization in single T cells appears not to be an all or none phenomenon. Rather, activation is incremental (analog signaling), the degree of Ca²⁺ mobilization probably being related to the number of stimulatory peptide-MHC complexes on the surface of the APC. The extent of calcium mobilization and lymphokine production (interleukin (IL)-2, IL-3, interferon-γ) correlated, at least at the population level.     

Generation of antigen-specific CD4+ T cell lines from naive precursors

The conditions required for sensitizing naive T cells to nominal antigen are poorly understood. In this report we describe an in vitro system for generating antigen-specific CD4⁺ T cells from previously unprimed individuals. Freshly isolated CD4⁺ T cells were cultured with keyhole limpet hemocyanin (KLH), sperm whale myoglobin (SWM), or human immunodeficiency virus (HIV) gp 160, antigens to which most persons have not been sensitized, in the presence of either dendritic cells (DC) or macrophages (MΦ). In short-term (< 8 days) cultures, CD4⁺ T cells or their CD4⁺, CD45RA (naive) subpopulation mounted significant proliferative responses to KLH, SWM, and HIV gp160, but only if the antigens were presented by DC. In contrast, CD4⁺, CD45RO (memory) T cells responded poorly to these antigens, although they responded vigorously to tetanus toxoid, a recall antigen, presented by either DC or MΦ. KLH- and SWM-specific CD4⁺ T cell lines were established from the starting population that had been sensitized in vitro, following repeated stimulation with antigen and MΦ in medium supplemented with interleukin-2 and interleukin-4. Despite the continued presence of these cytokines during T cell expansion, the expanded lines retained their ability to respond to the priming antigen in the absence of exogenous cytokines. When the CD45RA and CD45RO subpopulations were sensitized and expanded separately, the CD45RA cells alone gave rise to antigen-specific T cell lines, while the CD45RO cells proliferated nonspecifically. These results demonstrate that human naive CD4⁺ T cells can be sensitized in vitro to nominal antigens presented by DC and that the sensitized cells can be expanded into long-term lines that retain their antigen specificity.     

微小病变型肾病综合征患者IL－2的检测及其意义

３２例微小病变型肾病综合征（ＭＣＮＳ）患者，采用￣３Ｈ－ＴｄＲ掺入法测定其外周血Ｔ淋巴细胞产生白介素２（ＩＬ＿２）的浓度，结果显示本病患者Ｔ细胞产生ＩＬ＿２的能力显著降低，与对照组相比差异非常显著（Ｐ＜０．０１），故认为ＭＣＮＳ的发生与Ｔ细胞功能异常有关。     

Ontogeny and thymus-dependence of T cell surface antigens in Xenopus : flow cytometric studies on monoclonal antibody-stained thymus and spleen

Recently generated anti-Xenopus T cell monoclonal antibodies (mAbs) to the 120 kDA XTLA-1 determinant and against the putative CD5 and CD8 homologues, together with anti-IgM and anti-MHC class II mAbs, are used in dual colour flow cytometric experiments to characterize cell surface antigenic expression on lymphocytes in thymus and spleen of Xenopus laevis during larval and early adult life and also in metamorphosis-inhibited animals. Histological confirmation of T cell emergence early in larval ontogeny is supplied by cryostat sections stained for CD8. Five-day thymectomy i.e. prior to T-lineage cell differentiation in the thymus, abolishes T cell marker expression in the spleen for up to 1 year. Moreover, late larval (20 days) or early adult (3 months) thymectomy (i.e. removal after peripheralization of T cells has occurred) also leads to severe depletion of mAb-defined T cells in the spleen.     

Immunopathology of ocular sarcoidosis

Summary Sarcoidosis is a multisystem disease characterized by enhanced immune responses at sites of involvement. To elucidate the immunopathogenesis of ophthalmic lesions, cell infiltrates in biopsies from conjunctiva and other tissues involved (lungs, lymph nodes, skin) were studied in 26 patients with active sarcoidosis in order to define the surface phenotype and the distribution of cells in granulomatous lesions. Biopsy specimens were also stained for detection of immunoglobulins, complement and fibrinogen deposits. The data demonstrate a lymphocytes/macrophages interaction in the central core of granulomatous areas as the crucial event that initiates the maintains the state of inflammation: at all sites of disease activity is present a compartmentalization of T-cells expressing a helper-related phenotype which account for the great majority of infiltrating cells both in the early lesions (aggregate of macrophages surrounded by lymphocytic infiltrate) and in well-organized sarcoid granulomata. The presence of plasma cells and immunoglobulin deposits may represent an epiphenomenon in line with the helper infiltration, suggesting a local hyper-reactivity of the B-cells immune system. This study suggests some immunopathogenetic mechanisms leading to the formation and growth of conjunctival sarcoid granulomata.