In susceptible mice, Leishmania major induce very rapid interleukin-4 production by CD4+ T cells which are NK1.1-.

Susceptibility of BALB/c mice to infection with Leishmania major is associated with a T helper type 2 (Th2) response. Since interleukin-4 (IL-4) is critically required early for Th2 cell development, the kinetics of IL-4 mRNA expression was compared in susceptible and resistant mice during the first days of infection. In contrast to resistant mice, susceptible mice exhibited a peak of IL-4 mRNA in their spleens 90 min after i.v. injection of parasites and in lymph nodes 16 h after s.c. injection. IL-12 and interferon-gamma (IFN-gamma) down-regulated this early peak of IL-4 mRNA; the effect of IL-12 was IFN-gamma dependent. Treatment of resistant C57BL/6 mice with anti-IFN-gamma allowed the expression of this early IL-4 response to L. major. The increased IL-4 mRNA expression occurred in V beta 8, 7, 2- CD4+ cells in BALB/c mice and NK1.1- CD4+ cells in anti-IFN-gamma treated C57BL/6 mice. These results show that the NK1.1+ CD4+ cells, responsible for the rapid burst of IL-4 production after i.v. injection of anti-CD3, do not contribute to the early IL-4 response to L. major.

The alternatively spliced domain TnFnIII A1A2 of the extracellular matrix protein tenascin-C suppresses activation-induced T lymphocyte proliferation and cytokine production.

Several lines of evidences have suggested that T cell activation could be impaired in the tumor environment, a condition referred to as tumor-induced immunosuppression. We have previously shown that tenascin-C, an extracellular matrix protein highly expressed in the tumor stroma, inhibits T lymphocyte activation in vitro, raising the possibility that this molecule might contribute to tumor-induced immunosuppression in vivo. However, the region of the protein mediating this effect has remained elusive. Here we report the identification of the minimal region of tenascin-C that can inhibit T cell activation. Recombinant fragments corresponding to defined regions of the molecule were tested for their ability to inhibit in vitro activation of human peripheral blood T cells induced by anti-CD3 mAbs in combination with fibronectin or IL-2. A recombinant protein encompassing the alternatively spliced fibronectin type III domains of tenascin-C (TnFnIII A-D) vigorously inhibited both early and late lymphocyte activation events including activation-induced TCR/CD8 down-modulation, cytokine production, and DNA synthesis. In agreement with this, full length recombinant tenascin-C containing the alternatively spliced region suppressed T cell activation, whereas tenascin-C lacking this region did not. Using a series of smaller fragments and deletion mutants issued from this region, we have identified the TnFnIII A1A2 domain as the minimal region suppressing T cell activation. Single TnFnIII A1 or A2 domains were no longer inhibitory, while maximal inhibition required the presence of the TnFnIII A3 domain. Altogether, these data demonstrate that the TnFnIII A1A2 domain mediate the ability of tenascin-C to inhibit in vitro T cell activation and provide insights into the immunosuppressive activity of tenascin-C in vivo.

Reduced development of CD4-8-B220+ T cells but normal autoantibody production in lpr/lpr mice lacking major histocompatibility complex class I molecules.

The lpr gene has recently been shown to encode a functional mutation in the Fas receptor, a molecule involved in transducing apoptotic signals. Mice homozygous for the lpr gene develop an autoimmune syndrome accompanied by massive accumulation of double-negative (DN) CD4-8-B220+ T cell receptor-alpha/beta+ cells. In order to investigate the origin of these DN T cells, we derived lpr/lpr mice lacking major histocompatibility complex (MHC) class I molecules by intercrossing them with beta 2-microglobulin (beta 2m)-deficient mice. Interestingly, these lpr beta 2m-/- mice develop 13-fold fewer DNT cells in lymph nodes as compared to lpr/lpr wild-type (lprWT) mice. Analysis of anti-DNA antibodies and rheumatoid factor in serum demonstrates that lpr beta 2m-/- mice produce comparable levels of autoantibodies to lprWT mice. Collectively our data indicate that MHC class I molecules control the development of DN T cells but not autoantibody production in lpr/lpr mice and support the hypothesis that the majority of DN T cells may be derived from cells of the CD8 lineage.

Monoclonal antibodies against idiotypic determinant(s) of the T cell receptor from HPB-ALL cells induce IL2 production in Jurkat cells without apparent evidence of binding.

Two monoclonal antibodies (mAb) directed against idiotypic determinants of the T cell receptor (anti-Ti) from HPB-ALL cells induce interleukin 2 (IL2) production in Jurkat T cells without evidence of binding to these cells as judged by fluorescence-activated cell sorter (FACS) analysis, indirect antibody-binding radioimmunoassay and direct binding studies with 125I-labeled mAb. The IL2 response induced by these mAb observed both in the presence and absence of phorbol myristate acetate was in the range of that obtained when Jurkat cells were stimulated with phytohemagglutinin or anti-T3 mAb (Leu 4). The idiotypic specificity of the two anti-HPB-ALL Ti mAb was demonstrated by several criteria. Both mAb bound specifically to HPB-ALL cells as determined by radioimmunoassay or FACS analysis but not with 8 other T cell lines. The anti-HPB-ALL Ti mAb precipitated a disulfide-linked heterodimer of 85 kDa only from 125I-labeled HPB-ALL cells and not from other cell lines tested. Incubation of HPB-ALL cells with anti-T3 abrogated the expression of T3 and induced co-modulation of the idiotypic structures detected by the two anti-HPB-ALL Ti mAb. Conversely, incubation of HPB-ALL cells with either one of the anti-Ti mAb abrogated the expression of T3 and of the idiotypic structures. Our results suggest that mAb with an apparent unique specificity for the receptor of the immunizing T cell line HPB-ALL can activate Jurkat cells by a very weak cross-reaction with these cells, which is not detectable by conventional binding tests.

Indirect hydrogen monitoring by chemi-ionisation following an associative ionisation pathway after metastable helium atoms production by electron impact ionisation: Protonation and deuteration of carrier gas

Gas chromatography (GC) is an analytical tool very useful to investigate the composition of gaseous mixtures. However, hydrogen (H2) detection after a GC separation is only possible with a Thermal Conductivity Detector (TCD), a Helium Ionisation Detector (HID) or expensive Atomic Emission Detector (AED). Recently, indirect H2 detection by GC coupled to mass spectrometry (MS) was demonstrated but the mechanism of carrier gas protonation remained unclear. With electron impact as ionisation source of MS and helium (He) as GC carrier gas, H2 is not ionised according the expected Penning ionisation neither according to the Associative ionisation. Rearrangement ionisation (RI) was found to be the main channel for H2 and D2 ionisation under GC-MS conditions used in most of laboratories using GC-MS, leading to the formation of [He−H]+ and [He−D]+ ions.

Establishment of new crops for the production of natural rubber.

Natural rubber is a unique biopolymer of strategic importance that, in many of its most significant applications, cannot be replaced by synthetic alternatives. The rubber tree Hevea brasiliensis is the almost exclusive commercial source of natural rubber currently and alternative crops should be developed for several reasons, including: a disease risk to the rubber tree that could potentially decimate current production, a predicted shortage of natural rubber supply, increasing allergic reactions to rubber obtained from the Brazilian rubber tree and a general shift towards renewables. This review summarizes our knowledge of plants that can serve as alternative sources of natural rubber, of rubber biosynthesis and the scientific gaps that must be filled to bring the alternative crops into production.

Decreased intraocular pressure induced by nitric oxide donors is correlated to nitrite production in the rabbit eye.

PURPOSE: To evaluate the effect of intraocular administration of nitric oxide (NO) donors in the rabbit eye on intraocular pressure (IOP), inflammation, and toxicity. METHODS: Intravitreal and intracameral injections of two NO donors, SIN-1 and SNAP, and SIN-1C and BSS were performed. Clinical examination, IOP measurements, protein evaluation in aqueous humor, and histologic analysis of the ocular globes were realized. Nitric oxide release was demonstrated by nitrite production in the aqueous humor and in the vitreous using the Griess reaction. RESULTS: The drastic decrease of IOP, observed after a single NO donor injection, was correlated directly with nitrite production and, thus, to NO release. Injection of inactive metabolite of SIN-1, SIN-1C, which is not able to release NO, did not modulate IOP. When administered in the aqueous humor or in the vitreous, NO did not diffuse from one segment of the eye to another. No inflammation or histologic damage was observed as a result of a single NO donor administration. CONCLUSIONS: Nitric oxide is implicated directly in the regulation of IOP and its acute, and massive release into the rabbit eye did not induce inflammation or other growth toxic effects on the ocular tissues.