Myoblasts fail to stimulate T cells but induce tolerance

Recent interest in myoblast transfer and in the use of myoblastsas vehicles in gene therapy has made it important to understandthe potential immunogenicity of allogeneic or neoantlgen-expresslngmyoblasts. Given the problems of producing a pure populationof myoblasts, In this study we used a tumour-derived musclecell line (TE671), with phenotyplc features of myoblasts, whichwe transfected to express HLA-DR1. However, this cell line wasunable to stimulate either established HLA-DR1-specific alloreactlveT cell clones or a primary alloresponse. Nor could it presenthaemagglutlnln peptide HA 306–324 to DR1-restricted, HA306–324-speciflc T cell clones or lines. Indeed, prelncubatlonwith DR1-expressing TE671 and HA 306–324 rendered suchT cells tolerant as Judged by their subsequent inability toproliferate in response to a DR1⁺ B cell line plus peptide HA306–324. These results imply that myoblasts do not providecostlmulatory signals, and are therefore unlikely to stimulateallospeclfic T cells following myoblasts transplantation orto initiate neoantlgen-speclfic immune responses following Invivo transfection.     

Four-color flow cytometric analysis of peripheral blood donor cell chimerism

Passenger leukocytes have been demonstrated to play significant roles in initiating and also regulating immune reactions after organ transplantation. Reliable techniques to detect donor leukocytes in recipients after organ transplantation are essential to analyze the role, function, and behavior of these leukocytes. In this report we describe a simple, reliable method to detect donor cells with low frequencies using peripheral blood samples. Detection of small numbers of major histocompatibility complex (MHC) mismatched cells was first studied using four-color flow cytometry in artificially created cell mixtures. By selecting the CD45(+) population and simultaneous staining with several leukocyte lineage markers (CD3, CD4, CD8, CD56, and CD19), MHC-mismatched leukocytes were consistently detected in cell suspensions prepared from directly stained whole blood samples with a threshold sensitivity as low as 0.1%-0.2%. When the fresh peripheral blood mononuclear cells were separated by conventional Ficoll gradient purification, similar, but slightly lower levels of donor cells were detected. Blood samples obtained 1-5 months after liver, kidney, and intestine transplants revealed that the kind of organ allograft influenced levels and lineage pattern of the circulating donor cells. This procedure provided a simple and reliable method in determining early chimerism in transplant recipients. However, the detection of MHC-mismatched leukocytes of all lineages was much lower when frozen peripheral blood mononuclear cells were used.     

Down-modulation of CD4+ T helper type 2 and type 0 cells by T helper type 1 cells via Fas/Fasligand interaction

Fas was recently demonstrated to be the major target molecule engaged by CD4⁺ cytolytic T lymphocytes (CTL). We examined Fas expression on various cloned T cell subpopulations and their susceptibility to lysis by CD4⁺ or CD8⁺ CTL. A reciprocal relationship in Fas and Fas-ligand expression was observed in CD4⁺ T helper (Th)1- and Th2-type clones, and Fas mRNA was predominantly detected in Th2 clones, whereas Fas-ligand mRNA was principally found in Th1 clones. The two Th0 clones tested expressed both Fas and Fas-ligand, but only one exhibited cytolytic activity, whereas both were sensitive to CD4-mediated lysis. A functional consequence of the inverse Fas-Fas-ligand expression pattern was that Th2 and Th0 cells were sensitive to lysis by both Th1 CD4⁺ CTL and a CD8⁺ CTL clone in a Fas-dependent manner. These results suggest that cytolytic CD4⁺ Th1 cells may play an immunomodulatory role, regulating a Th2/Th0 response by Fas-mediated lysis.     

The effects of indoramin on histamine and antigen-induced changes in respiration in guinea-pigs

Indoramin, a drug which blocks alpha-adrenergie, histamine and serotonin receptors, was tested as a protective agent during challenge with bronchoconstrictor agents in guinea-pigs. In conscious guinea-pigs, the time of onset of respiratory distress during continuous administration of aerosolized solutions of histamine, serotonin or ovalbumin (with animals pre-sensitized to this antigen) was measured using a force-displacement transducer applied to the animal's back. This time interval for each guinea-pig was compared with and without indoramin pre-treatment. Indoramin was administered by intraperitoneal injection or by aerosol treatment. In anaesthetized animals under artificial respiration, respiratory distress was induced by intravenous injection of histamine and measured by the Konzett-Rössler technique. Indoramin treatment significantly protected guinea-pigs in both types of experiment from the effects of each challenging agent.     

Emphysematous lung destruction by cigarette smoke. The effects of latent adenoviral infection on the lung inflammatory response.

This study was designed to test the hypothesis that cigarette smoke-induced inflammation and emphysema are amplified by the presence of latent adenoviral (Ad) infection, and to determine whether this emphysematous process can be reversed by all-trans-retinoic acid (RA) treatment. The results confirm that in guinea pigs, chronic cigarette-smoke exposure caused lesions similar to human centrilobular emphysema. They also show that latent Ad infection combined with cigarette-smoke exposure caused an excess increase in lung volume (P < 0.001), air-space volume (P < 0.001), and lung weight (P < 0.01), and further decrease in surface-to-volume ratio (P < 0.001) compared with smoke exposure alone. RA treatment failed to reverse these emphysematous changes. Analysis of inflammatory response in parenchymal and airway tissue showed that smoking caused an increase of polymorphonuclear leukocytes (PMNs) (P < 0.0002), macrophages (P < 0.001), and CD4 cells (P < 0.0009), and that latent Ad infection independently increased PMNs (P < 0.001), macrophages (P = 0.003), and CD8 cells (P < 0.001). We conclude that latent Ad infection amplifies the emphysematous lung destruction and increases the inflammatory response produced by cigarette-smoke exposure. In this study, the increase in CD4 was associated with cigarette smoke and the increase in CD8 cells with latent Ad infection.     

B cell early response gene expression coupled to B cell receptor,CD40 and interleukin-4 receptor co-stimulation: evidence for a role of the egr-2/krox20 transcription factor in B cell proliferation

B lymphocytes are activated following antigen stimulation of the B cell receptor but require co-stimulation with accessory molecules provided by interleukin (IL)-4/CD40 ligand for cell cycle progression and proliferation. By analyzing a panel of 11 early response genes induced by cross-linking of surface immunoglobulin, we show that CD40 signaling alone induces only 2 genes, c-myc together with an anonymous gene, 3L3, and that these are distinct from the set of genes induced in response to IL-4. Co-stimulation with the proliferative combination of anti-μ, IL-4 + CD40 signaling led to a fourfold enhancement of egr-2/krox20 expression over that seen with anti-μ alone. Egr-2 expression/activity was selectively inhibited by the immunosuppressive drug cyclosporin A, and antisense oligonucleotide blockade of Egr-2 activity elicited a dose-dependent inhibition of B cell proliferation. Taken together, these observations show that the early gene regulatory programs coupled to different surface receptors on B cells are largely distinct from each other, but that certain genes, exemplified by egr-2, may represent a point of convergence in the integration of different signaling pathways into the B cell proliferative response.     

Use of multiepitope polyproteins in serodiagnosis of active tuberculosis

Screening of genomic expression libraries from Mycobacterium tuberculosis with sera from tuberculosis (TB) patients or rabbit antiserum to M. tuberculosis led to the identification of novel antigens capable of detecting specific antibodies to M. tuberculosis. Three antigens, Mtb11 (also known as CFP-10), Mtb8, and Mtb48, were tested together with the previously reported 38-kDa protein, in an enzyme-linked immunosorbent assay (ELISA) to detect antibodies in TB patients. These four proteins were also produced as a genetically fused polyprotein, which was tested with two additional antigens, DPEP (also known as MPT32) and Mtb81. Sera from individuals with pulmonary and extrapulmonary TB, human immunodeficiency virus (HIV)-TB coinfections, and purified protein derivative (PPD)-positive and PPD-negative status with no evidence of disease were tested. In samples from HIV-negative individuals, the ELISA detected antibodies in >80% of smear-positive individuals and >60% smear-negative individuals, with a specificity of approximately 98%. For this group, smears detected 81.6% but a combination of smear and ELISA had a sensitivity of approximately 93%. The antigen combination detected a significant number of HIV-TB coinfections as well as antibodies in patients with extrapulmonary infections. Improved reactivity in the HIV-TB group was observed by including the antigen Mtb81 that was identified by proteomics. The data indicate that the use of multiple antigens, some of which are in a single polyprotein, can be used to facilitate the development of a highly sensitive test for M. tuberculosis antibody detection.