No description available.

Measles-associated morbidity and mortality can be decreased in response to treatment with vitamin A. However, the mechanism underlying this beneficial effect is unknown. In this work, we investigate the molecular interaction between measles virus (MeV) and retinoids in vitro. Our first goal was to assess whether retinoids influence the in vitro replication of MeV. We found all-trans retinoic acid (ATRA), as well as other natural and synthetic retinoids, inhibited MeV replication in primary cells and a range of cell lines. This inhibitory effect was mediated through retinoid nuclear receptor signaling, and retinoic acid receptor alpha (RARalpha) in particular. Next, we sought to determine the role of type I interferon (IFN), since both MeV and retinoids can modulate IFN signaling. Type I IFN blocking antibodies abrogated the inhibitory effects of ATRA on MeV replication. IFN-stimulated genes (ISG) were upregulated by ATRA in MeV-infected cell cultures when compared to either treatment or infection alone. Using a transwell system, we determined that this increased gene expression occurred in initially uninfected bystander cells. The ATRA-treated bystander cells did not support substantial viral replication when subsequently challenged with MeV. Finally, we identified retinoid-induced gene I (RIG-I) as a link between the RARalpha - and IFN-dependent mechanism of MeV inhibition by retinoids. We found that RIG-I can be transcriptionally regulated by ATRA. Furthermore, RARalpha function was necessary for the induction of RIG-I by MeV and ATRA, and could bind to the RIG-I promoter. A retinoic acid response element (RARE) in the RIG-I promoter region was identified, and RIG-I promoter constructs were shown to produce luciferase in response to ATRA. Finally, we showed that functional RIG-I was necessary for ATRA to inhibit MeV replication. In summary, we have demonstrated that transcriptional regulation of RIG-I / Les taux de morbidité et de mortalité associés à la rougeole peuvent diminuer à la suite d'un traitement à la vitamine A ; or, le mécanisme à l'origine de cet effet bénéfique est encore inconnu. Par ce travail, nous avons voulu étudier les mécanismes résultant de l'interaction du virus de la rougeole (MeV) et des rétinoïdes in vitro. Nous avions d'abord comme objectif de déterminer si les rétinoïdes avaient un impact sur la réplication du MeV in vitro . Nous avons démontré que le ligand spécifique, l'acide tout-trans rétinoïque (ATRA), ainsi que d'autres rétinoïdes naturels et synthétiques inhibent la réplication du MeV chez des cellules primaires de même que chez un grand nombre de lignées cellulaires. Nous avons aussi démontré que la signalisation par les récepteurs nucléaires des rétinoïdes, en particulier le récepteur alpha de l'acide rétinoïque (RARalpha), était responsable de l'effet inhibiteur observé. Nous avons ensuite voulu déterminer le rôle de l'interféron de type I (IFN) puisqu'il est connu que MeV et les rétinoïdes peuvent moduler la signalisation de cet IFN de différentes façons. Nos recherches ont permis de démontrer que des anticorps bloquant la signalisation par l'IFN de type I renversent les effets inhibiteurs de l'ATRA sur la réplication du MeV, démontrant ainsi l'importance de la signalisation par cet IFN. En outre, l'ATRA augmente l'expression des gènes stimulés par l'IFN de type I (ISG) chez des cellules en culture infectées par le MeV comparativement aux cellules uniquement traitées à l'ATRA ou uniquement infectées par le MeV. L'utilisation d'un système Transwell a aussi permis de déterminer que l'augmentation de l'expression de ces gènes survient chez des cellules de voisinage non-infectées initialement par le MeV. Lorsque ces cellules, traitées à l'ATRA, étaient par la suite infectées au MeV, on n'y observait pas d

A number of T-cell membrane molecules influence the outcome of antigen recognition by TCR/CD3 complex. CD4, by virtue of its non-covalent association with the protein tyrosine kinase lck has the capacity to enhance TCR$ alpha beta$ signalling. The extracellular domain of CD4 interacts with monomorphic determinants of Major Histocompatibility complex class-II molecules such that antigen presented in association with MHC class-II to CD4$ sp+$ T-cells results in the coaggregation of CD4 and TCR/CD3, thus juxtaposing lck and the antigen-receptor complex. Anti-CD4 antibodies abrogate both antigen and anti-TCR-induced T-cell activation. Studies using antigen specific T-cell clones that express either no CD4, wild type CD4 or mutated CD4 that cannot associate with lck (Db CYS) indicate that CD4 sequesters the majority of cellular lck and when not coaggregated with TCR/CD3, prevents the generation of prerequisite signals. / Results presented in this thesis indicate that while CD4-associated lck is providing prerequisite signals for TCR/CD3 signalling, the contribution of CD4 must be more than simply providing a shuttle for lck. Specifically, anti-CD4 inhibits the antigen response of Db CYS CD4-expressing clones. This result cannot be accounted for either by CD4 sequestration of lck, or reduction of avidity of the interaction between the T-cell and the antigen presenting cell, since CD4$ sp-$ variants exhibit an antigen response comparable to that of CD4$ sp+$ variants. Rather, they suggest a novel role for the ectodomain of CD4 in antigen-induced T-cell activation.

Mice homozygous for the scid (severe combined immunodeficiency) mutation are generally unable to produce B lymphocytes, a condition attributed to defective rearrangements of immunoglobulin genes in precursor B cells. Some early B lineage cells are present in the bone marrow (BM), however. In scid mice, we defined three subsets of early progenitor B cells lacking $ mu$ heavy chains (pro-B cells) based on the expression of terminal deoxynucleotidyl transferase (TdT) and B220 glycoprotein: (a) early (TdT+B220$-$), (b) intermediate (TdT+B220+), and (c) late (TdT$-$B220+). Double immunofluorescence labelling of BM cell suspensions has shown normal numbers of early and intermediate pro-B cells, substantially reduced numbers of late pro-B cells, and an absence of pre-B cells and B cells. Nearly all defective cells, thus, abort at the late pro-B cell stage. Early and intermediate pro-B cells accumulated in metaphase in near-normal numbers after intraperitoneal vincristine administration, apparently not regulated by feedback signals from the B cell pool. / The scid mouse provided a system for studies on regulation of pro-B cells and the effectiveness of the deletion mechanism. It was determined that the defective pro-B cells of scid mice were susceptible to the stimulatory effects of an exogenous agent, sheep red blood cells, and a stromal cell-derived growth factor for precursor B cells, interleukin-7, as previously observed in normal mice in vivo. In addition, pro-B cells of scid mice were driven to proliferate by the dysregulated constitutive expression of the c-myc oncogene. In each case, however, all cells aborted soon after reaching the late pro-B stage. Mechanisms by which aberrant cells are deleted from the B lineage, safeguarding against entry of potentially dysregulated cells into the peripheral B cell pool, thus, could not be overwhelmed or evaded by increased proliferative activity of pro-B cells.

Neutrophil aggregation has been widely evaluated from changes in light transmission. Using direct particle counting, we demonstrated that light transmission does not accurately reflect aggregation, and showed that in contrast to previous reports, newborn neutrophils do not aggregate irreversibly. We developed a flow cytometric technique to measure the kinetics of neutrophil aggregation, including latent times for onset of aggregation, initial forward and reversal rates, and maximal extents of aggregation. The kinetics of neutrophil aggregation were related to changes in initial cell concentration, stir speed (shear), and activator type and concentration. Physiologic activators stimulated reversible aggregation, accompanied by an exponential decay in aggregatory potential with increasing time. The fraction of occupied activator receptors was found to correspond to the fraction of maximal rates or extent of aggregation. Monoclonal antibodies were used to show that neutrophil aggregation is mediated by the Mac-1 integrin (CD11b/CD18). Direct measurements of aggregation have enhanced our understanding of the (patho)physiologic process of neutrophil aggregation.

The potential relationship between the Epstein-Barr Virus (EBV) and the Human Immunodeficiency Virus type 1 (HIV-1) in lines of EBV-carrying B cells that had been super-infected by HIV-1 was investigated. We found that such cells can produce high levels of viral particles, over long periods, with a minimal cytopathic effect and were less susceptible to HIV-1 infection than primary cultures of human peripheral blood mononuclear cells (PBMC). / We also investigated whether an alternative receptor, other than the well-known CD4 receptor, could permit HIV-1 infection of B cells immortalized by EBV. We detected a mechanism of complement-mediated antibody-dependent enhancement of HIV-1 infection in these cells implicating the CD4 receptor, the complement receptor type 2, and the alternate pathway of complement. / The fact that AZT is actually the most widely used drug in treating HIV-1 infections prompted us to investigate the ability of AZT to prevent infection and replication of HIV-1 in EBV-positive B cells. Three concentrations of AZT (1, 5 and 10 $ mu$M) prevented infection by one clinical isolate (334). In contrast, no such inhibitory effect was observed with each of a second clinical isolate (336) or with the HIV-III$ sb{ rm B}$ laboratory strain of HIV-1. Nevertheless, in these two particular cases, AZT significantly delayed and attenuated viral expression. / Finally, we determined that exposure of PBMC from HIV-1-infected individuals to preparations of HSV-1, HSV-2, or CMV stimulated the cells to become active producers of HIV-1 and point to a possible role for these viruses as co-factors in the pathogenesis of AIDS.

The relationship between various immune functions, tissue damage, and splenomegaly was investigated during the course of Graft-versus-host (GVH) reactions. / The GVH-associated tissue lesions appeared at the time when both the T- and B-cell functions were severely suppressed and NK cell activity was at its peak and/or highly augmented. The development of tissue lesions correlated with donor NK cell activity. On the other hand, splenomegaly developed independently of both the NK cell activity as well as tissue lesions. / Prolonged immunosuppression was associated with thymic dysplasia, but not splenomegaly. The immune functions recovered gradually, following severe suppression, and coincided with the gradual recovery of the thymus. The immune functional recovery was observed in the following order: LPS responsive B-cell functions; ConA responsive T-cell functions; PHA responsive T-cell functions; and finally T-cell dependent B-cell responses. T-cell functions of immunodeficient GVH mice could be restored only when the thymic medullary regeneration had occurred. In contrast, the restoration of NK cell activity of NK-depressed mice was independent of thymic dysplasia. / These studies provide information regarding the possible mechanisms involved in inducing immunosuppression, tissue damage, and splenomegaly following GVH induction.

Soluble lung tumor antigen activity, as determined by the leukocyte adherence inhibition (LAI) assay, was enriched by physicochemical methods from chemically-defined spent medium of a lung cancer cell line (NCI-H69). To identify the polypeptide carrying the antigenic determinant, BALB/c mice were immunized with the enriched isolate and their splenic lymphocytes were fused with mouse plasmacytoma cells. / Eight hybrids were cloned and produced MAbs that immunoprecipitated principally a single chain of MW 40,000 (p40) as well as minor chains of MW 25,000 (p25) and MW 13,000 (p13) which were probably degradation products of p40. On 2D gels, p40 was composed of 7 spots with a pI of 6.1 to 7.6, which was not altered by neuraminidase digestion. Affinity chromatography with MAb anti-p40 absorbed p40 and LAI activity. The bound and recovered fraction was enriched for p40 and LAI activity. Affinity-purified p40 contained the previously identified p25 and p13 as well as a MW 32,000 polypeptide (p32). MAb anti-p40 was directed to a common framework determinant on p40 since MAb anti-p40 bound to cancer cells from other organs. The lung cancer organ-specific determinant recognized by leukocytes from lung cancer patients was not recognized by the MAb. Affinity purified p40 triggered the LAI response for leukocytes from patients with lung cancer but not for leukocytes from control subjects or patients with colon cancer or malignant melanoma in blind testing. Partial cross-reactivity was observed with leukocytes from patients with breast cancer. Thus, a p40 molecule has been purified that is expressed on the membranes of lung cancer cells and triggers immunologically-mediated LAI.

The murine F$ sb1$ hybrid model of graft-versus-host (GVH) disease was used to investigate the nature of GVH-induced T cell immunodeficiency. Chronic GVH reactions were induced in BAF$ sb1$ mice by the i.v. injection of 50 $ times$ 10$ sp6$ parental A strain lymphoid cells. At various days (43-139) after GVH induction the thymi and spleens were excised and used for in vitro functional studies. In addition, both lymphoid and non-lymphoid organs were evaluated histologically. Interleukin 1 (IL-1) and 2 (IL-2) were used as probes to assess the functional status of the peanut agglutinin positive (PNA$ sp-$) and peanut agglutinin negative (PNA$ sp+$) subpopulations. The results obtained strongly suggest that GVH-induced T cell immunodeficiency is due in part to a decreased responsiveness to IL-1 and IL-2, and to a marked deficiency in IL-2 production.

No description available.