CTLA-4 is required for the induction of high dose oral tolerance

Mucosal and systemic administrations of high dose antigens induce long- lasting peripheral T cell tolerance. We and others have shown that high dose peripheral T cell tolerance is mediated by anergy or deletion and is preceded by T cell activation. Co-stimulatory molecules B7-1 (CD80)/B7-2 (CD86) and their counter-receptors CD28/CTLA-4 play pivotal roles in T cell activation and immune regulation. In the present study, we examined the roles of the B7 co-stimulation pathway in the generation of high dose peripheral T cell tolerance. We found that blocking B7:CD28/CTLA-4 interaction at the time of tolerance induction partially prevented T cell tolerance, whereas selective blockade of B7:CTLA-4 interaction completely abrogated peripheral T cell tolerance induced by either oral or i.p. antigens. These results suggest that CTLA-4-mediated feedback regulation plays a crucial role in the induction of high dose peripheral T cell tolerance.      

A new virtual reality approach for planning of cardiac interventions

A novel approach to three-dimensional (3D) visualization of high quality, respiratory compensated cardiac magnetic resonance (MR) data is presented with the purpose of assisting the cardiovascular surgeon and the invasive cardiologist in the pre-operative planning. Developments included: (1) optimization of 3D, MR scan protocols; (2) dedicated segmentation software; (3) optimization of model generation algorithms; (4) interactive, virtual reality visualization.The approach is based on a tool for interactive, real-time visualization of 3D cardiac MR datasets in the form of 3D heart models displayed on virtual reality equipment. This allows the cardiac surgeon and the cardiologist to examine the model as if they were actually holding it in their hands. To secure relevant examination of all details related to cardiac morphology, the model can be re-scaled and the viewpoint can be set to any point inside the heart. Finally, the original, raw MR images can be examined on line as textures in cut-planes through the heart models.     

Granulocyte-macrophage colony-stimulating factor enhances basophil histamine release induced by non-IgE-dependent stimulators

Some cytokines are known to affect IgE-mediated basophil histamine release. The effect of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) on human basophil and masct cell histamine release was studies further. Blood leukocytes with approximately 2% basophils from 9 healthy individuals were incubated with recombinant human GM-CSF (0.3–30 U/ml) in combination with A23187 (10^–7–10^–6 M) or washedStaphylococcus aureus whole bacteria (0.3–2.5 mg/ml). Histamine release was measured spectrofluorometrically. GM-CSF in itself did not induce histamine release. The addition of GM-CSF to cells stimulated with A 23187 caused a dose-dependent enhancement amounting to mean 70% at 3 U/ml and mean 170% at 30 U/ml (P<0.05). GM-CSF enhanced the bacteria-induced histamine release by 30% at U/ml and by 65% at 3 U/ml (P<0.05). The enhancement did not depend on cell-bound IgE or LPS contamination. In preliminary mast cell experiments with lung tissue we did not find an enancing effect of GM-CSF on IgE-mediated histamine release.     

Mitochondrial DNA in the aquatic fungus Allomyces

Summary The mitochondrial DNA from seven species of the aquatic phycomycete Allomyces has been isolated and characterized by restriction enzyme analysis. Comparison of the mitochondrial DNA restriction enzyme fragmentation patterns showed pronounced differences not only among species but also among four isolates of A. arbuscula. The mitochondrial DNAs range in size from 39 kbp in A. neo-moniliformis to 56 kbp in A. macrogynus.A physical map of the mitochondrial DNA of Allomyces arbuscula strain Costa Rica 21 has been constructed. The genome is circular and has a size of 49.2 kbp. The genes coding for the small and large ribosomal RNAs, cytochrome oxidase subunits 1, 2, and 3, apocytochrome b, and ATPase subunits 6 and 9 were localized in the mitochondria) DNA by heterologous hybridization with specific mitochondria) gene probes from Saccaromyces cerevisiae and Neurospora crassa. Comparison of the gene map of the closely related species Blastocladiella emersonii with that of A. arbuscula indicates a similar gene order in the two organisms.     

Physical activity and plasma interleukin-6 in humans – effect of intensity of exercise

The present study included data from three marathon races to investigate the hypothesis that a relationship exists between running intensity and elevated concentrations of interleukin (IL)-6 in plasma. The study included a total of 53 subjects whose mean age was 30.6 [95% confidence interval (CI) 1.4] years, mean body mass 77.7 (95%CI 2.0) kg, mean maximal oxygen uptake (V˙O_2max) 59.3 (95%CI 1.4) ml · min⁻¹ · kg⁻¹, and who had participated in the Copenhagen Marathons of 1996, 1997 or 1998, achieving a mean running time of 206 (95%CI 7) min. Running intensity was calculated as running speed divided by V˙O_2max. The concentration of IL-6 in plasma peaked immediately after the run. There was a negative correlation between peak IL-6 concentration and running time (r=−0.30, P < 0.05) and a positive correlation between peak IL-6 concentration and running intensity (r=0.32, P < 0.05). The IL-1 receptor antagonist (IL-1ra) plasma concentration peaked 1.5 h after the run and there was a positive correlation between the peak plasma concentrations of IL-6 and IL-1ra (r=0.39, P < 0.01). Creatine kinase (CK) plasma concentration peaked on the 1st day after the run, but no association was found between peak concentrations of IL-6 and CK. In conclusion, the results confirmed the hypothesized association between plasma IL-6 concentration and running intensity, but did not confirm the previous finding of a connection between IL-6 plasma concentration and muscle damage. Accepted: 6 August 2000     

Down-regulation of natural killer cell activity by autologous polymorphonuclear leucocytes

It has been recently reported that neutrophils are involved in the regulation of NK cell activity. However, the mechanism of such regulation is unclear. The present study was designed to investigate the mechanisms involved in the regulation of NK cytotoxicity by human neutrophils. The role of indomethacin, an anti-inflammatory drug, in this interaction was studied. NK cells were purified from peripheral blood obtained from normal individuals. NK cell cytotoxicity was tested on K 562 cell line by Cr release assay. Autologous neutrophils obtained from peripheral blood were stimulated by opsonized zymosan either in the presence or absence of indomethacin. The role of neutrophil supernatant containing oxygen radicals and prostaglandins on NK cytotoxicity was examined. It was shown that supernatants from stimulated neutrophils significantly inhibited (P less than 0.05) the autologous NK cell cytotoxicity. The presence of indomethacin in the in vitro reaction mixture, or given orally to donors, partially or completely abolished the inhibitory effect of neutrophil supernatant. Indomethacin inhibited prostaglandin E2 release, and luminol-enhanced, myeloperoxidase-mediated chemiluminescence of activated PMN. Diafiltration of neutrophil supernatant showed that the inhibitory activity was present in the fraction containing molecules lower than 5,000 daltons. In conclusion, our findings indicate that down-regulation of NK cytotoxicity is mediated by prostaglandins produced by stimulated neutrophils and possibly by oxygen radicals.     

Inhibition of human natural killer cell activity by Pseudomonas aeruginosa alkaline protease and elastase.

The present study was designed to examine the effect of Pseudomonas aeruginosa alkaline protease (AP) and elastase (Ela) on human natural killer (NK) cell activity in vitro. AP and Ela were found to inhibit NK cell function. Addition of alpha interferon and interleukin-2 did not abolish this inhibition of NK cell activity. Adhesion of effector to target cells was studied in a single-cell agarose assay of monocyte-depleted NK-cell-enriched cell populations. AP and Ela were shown to inhibit effector/target cell conjugate formation. Furthermore, AP and Ela inhibited the binding of the monoclonal antibody Leu-11, which reacts with the Fc receptor of NK cells. The inhibition of NK cell binding to the target cell by P. aeruginosa proteases is most likely due to proteolytic cleavage of the surface receptors involved in the binding of the effector cell to the target cell.     

Detection of Campylobacter spp. in chicken fecal samples by real-time PCR

A real-time PCR assay for detecting thermophilic Campylobacter spp. directly in chicken feces has been developed. DNA was isolated from fecal material by using magnetic beads followed by PCR with a prealiquoted PCR mixture, which had been stored at -18 degrees C. Campylobacter could be detected in less than 4 h, with a detection limit of 100 to 150 CFU/ml, in a fecal suspension. A bacterial internal control was added before DNA extraction to control both DNA isolation and the presence of PCR inhibitors in the samples. The assay was performed on 111 swab samples from a Danish surveillance program and compared to conventional culturing using selective enrichment. There was no statistically significant difference in performance between real-time PCR and culture by selective enrichment, and the diagnostic specificity was 0.96 with an agreement of 0.92. Therefore, the assay should be useful for screening poultry flocks for the presence of Campylobacter.     

Expression of interleukin-15 in human skeletal muscle – effect of exercise and muscle fibre type composition

The cytokine interleukin-15 (IL-15) has been demonstrated to have anabolic effects in cell culture systems. We tested the hypothesis that IL-15 is predominantly expressed by type 2 skeletal muscle fibres, and that resistance exercise regulates IL-15 expression in muscle. Triceps brachii, vastus lateralis quadriceps and soleus muscle biopsies were obtained from normally physically active, healthy, young male volunteers ( n = 14), because these muscles are characterized by having different fibre-type compositions. In addition, healthy, normally physically active male subjects ( n = 8) not involved in any kind of resistance exercise underwent a heavy resistance exercise protocol that stimulated the vastus lateralis muscle and biopsies were obtained from this muscle pre-exercise as well as 6, 24 and 48 h post-exercise. IL-15 mRNA levels were twofold higher in the triceps (type 2 fibre dominance) compared with the soleus muscle (type 1 fibre dominance), but Western blotting and immunohistochemistry revealed that muscle IL-15 protein content did not differ between triceps brachii, quadriceps and soleus muscles. Following resistance exercise, IL-15 mRNA levels were up-regulated twofold at 24 h of recovery without any changes in muscle IL-15 protein content or plasma IL-15 at any of the investigated time points. In conclusion, IL-15 mRNA level is enhanced in skeletal muscles dominated by type 2 fibres and resistance exercise induces increased muscular IL-15 mRNA levels. IL-15 mRNA levels in skeletal muscle were not paralleled by similar changes in muscular IL-15 protein expression suggesting that muscle IL-15 may exist in a translationally inactive pool.