Mechanism of suppression of cell-mediated immunity by measles virus.

The mechanisms underlying the profound suppression of cell-mediated immunity (CMI) accompanying measles are unclear. Interleukin-12 (IL-12), derived principally from monocytes and macrophages, is critical for the generation of CMI. Measles virus (MV) infection of primary human monocytes specifically down-regulated IL-12 production. Cross-linking of CD46, a complement regulatory protein that is the cellular receptor for MV, with antibody or with the complement activation product C3b similarly inhibited monocyte IL-12 production, providing a plausible mechanism for MV-induced immunosuppression. CD46 provides a regulatory link between the complement system and cellular immune responses.

High volume and low concentration of anaesthetic solution in the perivascular interscalene sheath determines quality of block and incidence of complications.

BACKGROUND AND OBJECTIVE: In the perivascular sheath of the brachial plexus, the volume of anaesthetic solution determines the quality of anaesthetic cover. Fibrous septa may divide the perivascular space into compartments, leading to inadequate diffusion of the anaesthetic solution. The aim of our study was to obtain good anaesthesia and less complications using high volume of low concentration anaesthetic solution, overcoming the obstacle of the septa with a double approach to the scalene sheath. METHODS: Sixty patients scheduled for shoulder capsuloplasty received both Winnie interscalene brachial plexus block and Pippa proximal cranial needle approach. The patients were randomly assigned to two groups. A constant dose of local anaesthetic was administered to each group: Group I (30 patients) received high volume (60 mL of anaesthetic solution) and Group II (30 patients) received low volume of solution (30 mL of anaesthetic solution). Sensory and motor block in the upper limb and complications were evaluated. RESULTS: In all the patients the quality of anaesthesia obtained at the surgical site was excellent. In Group I also the areas supplied by the medial cutaneous nerves of the arm and forearm, ulnar, median and radial nerves were blocked (P < 0.002). Complications were only observed in Group II and consisted of bradycardia and hypotension (66% of the patients) and phrenic nerve paresis (27% of the patients). CONCLUSIONS: The lower concentration of the anaesthetic solution avoids complications while increased volume provides good analgesic cover. The combination of the Winnie interscalene plexus block and the Pippa proximal cranial needle approach should contribute to fill up the scalene sheath overcoming the septa obstacles.

Kinesin movement on glutaraldehyde-fixed microtubules.

Glutaraldehyde-cross-linked microtubules were investigated as substrates for kinesin motility. Microtubules, formed in vitro from chicken brain tubulin, were stabilized with Taxol and chemically fixed with glutaraldehyde. The degree of tubulin monomer cross-linking as a function of time and glutaraldehyde concentration was characterized using polyacrylamide gel electrophoresis. Atomic force microscopy of fixed microtubules indicated that the cross-linking is sufficient to stabilize the gross structure of the microtubules against air drying or a distilled water challenge. Kinesin movement on immobilized, fixed microtubules was determined using a kinesin-coated bead motility assay observed with differential interference contrast microscopy. Within measurement error, kinesin bead movement velocities were independent of the degree of microtubule cross-linking. Binding affinity, however, decreased with increased cross-linking. Although air- and water-challenged microtubules did not support kinesin motility, a dilute suspension of glutaraldehyde-fixed microtubules in buffer supported kinesin motility for at least 2 days without any substantial degradation of activity. Fixed microtubules may be useful for several applications, including affinity purification of microtubule-associated proteins and motility measurements under extreme conditions of temperature and other variables.

Potent suppression of IL-12 production from monocytes and dendritic cells during endotoxin tolerance.

Endotoxin tolerance, the down-regulation of a subset of endotoxin-driven responses after an initial exposure to endotoxin, may provide protection from the uncontrolled immunological activation of acute endotoxic shock. Recent data suggest, however, that the inhibition of monocyte/macrophage function associated with endotoxin tolerance can lead to an inability to respond appropriately to secondary infections in survivors of endotoxic shock. IL-12 production by antigen-presenting cells is central to the orchestration of both innate and acquired cell-mediated immune responses to many pathogens. IL-12 has also been shown to play an important role in pathological responses to endotoxin. We therefore examined the regulation of IL-12 during endotoxin tolerance. Priming doses of lipopolysaccharide ablate the IL-12 productive capacity of primary human monocytes. This suppression of IL-12 production is primarily transcriptional. Unlike the down-regulation of TNF-alpha under such conditions, the mechanism of IL-12 suppression during endotoxin tolerance is not dependent upon IL-10 or transforming growth factor-beta, nor is IL-12 production rescued by IFN-gamma or granulocyte-macrophage colony-stimulating factor. Of note, human dendritic cells also undergo endotoxin tolerance, with potent down-regulation of IL-12 production. Endotoxin tolerance-related suppression of IL-12 production provides a likely mechanism for the anergy seen during the immunological paralysis which follows septic shock.

Type I interferons and IL-12: convergence and cross-regulation among mediators of cellular immunity.

Therapeutic use of type I IFN (IFN-alpha/beta) has become common. Many of the diverse diseases targeted are marked by pathogenetic abnormalities in cell-mediated immunity (CMI), these cellular immune responses either causing injury to the host, lacking sufficient vigor for virus or tumor clearance, or both. In general, therapeutic efficacy is limited. It is thus notable that the pleiotropic effects of type I IFN on CMI remain poorly understood. We characterized the effects of type I IFN on the production of IL-12, the central immunoregulatory cytokine of the CD4(+) T cell arm of CMI. We show that type I IFN are potent inhibitors of IL-12 production by human monocytes/macrophages. The underlying mechanism involves transcriptional inhibition of the IL-12p40 gene, marked by down-regulation of PU.1 binding activity at the upstream Ets site of the IL-12p40 promoter. Type I IFN have previously been shown to be able to substitute for IL-12 in driving IFN-gamma production from T and NK cells. The ability of IFN-alpha/beta to suppress IL-12 production while up-regulating IFN-gamma production suggests a possible mechanistic basis for the difficulties of employing these cytokines in diseases involving abnormalities of CMI.

Identification of complement factor 5 as a susceptibility locus for experimental allergic asthma.

The prevalence and severity of allergic asthma continue to rise, lending urgency to the search for environmental triggers and genetic substrates. Using microarray analysis of pulmonary gene expression and single nucleotide polymorphism-based genotyping, combined with quantitative trait locus analysis, we identified the gene encoding complement factor 5 (C5) as a susceptibility locus for allergen-induced airway hyperresponsiveness in a murine model of asthma. A deletion in the coding sequence of C5 leads to C5-deficiency and susceptibility. Interleukin 12 (IL-12) is able to prevent or reverse experimental allergic asthma. Blockade of the C5a receptor rendered human monocytes unable to produce IL-12, mimicking blunted IL-12 production by macrophages from C5-deficient mice and providing a mechanism for the regulation of susceptibility to asthma by C5. The role of complement in modulating susceptibility to asthma highlights the importance of immunoregulatory events at the interface of innate and adaptive immunity in disease pathogenesis.