Lipids from Mycobacterium leprae cell wall are endowed with an anti-inflammatory property and inhibit macrophage function in vivo.

In general, the majority of bacteria are pre-inflammatory when injected in experimental animals. However, Mycobacterium leprae has no inflammatory effect when injected into mouse footpad, but using the delipidated mycobacteria we observed a mild significant increase in footpad oedema. Other mycobacteria, Mycobacterium bovis-BCG or M. tuberculosis induce a strong paw oedema. Furthermore, M. leprae reduced locally the BCG-induced inflammatory reaction in mouse footpad, whereas delipidated M. leprae did not influence this reaction. Both M. leprae and M. leprae cell wall lipids blocked immune phagocytosis in vivo by inflammatory macrophages (from an induced focus). In contrast delipidated M. leprae stimulated the phagocytosis reaction. Neither intact M. leprae. delipidated M. leprae, nor its lipids had any toxic effect on macrophages or on cell migration. Although M. leprae did not interfere on cell influx and cell type in an induced-inflammatory site, this mycobacterium led to the appearance of a distinct cell population in vivo. The hypothesis is that M. leprae would transform macrophages in epithelioid cells, suggested by morphology analysis of cells by fluorescence-activated cell sorter and observed under optic microscopy.     

Interleukin-10 secreted by B-1 cells modulates the phagocytic activity of murine macrophages in vitro

As demonstrated previously in our laboratory, B-1 cells migrate from the peritoneal cavity of mice and home to a distant site of inflammation to become macrophage-like cells. However, the influence that these cells might have on the kinetics and fate of the inflammatory process is not known. Considering that macrophages are pivotal in the inflammatory reaction, we decided to investigate the possible influence B-1 cells could have on macrophage activities in vitro. Our results show that peritoneal macrophages from Xid mice, a mouse strain deprived of B-1 cells, have higher phagocytic indexes for zymozan particles when compared with macrophages from wild-type mice. Moreover, macrophages from wild-type mice have a lower ability to release nitric oxide and hydrogen peroxide when compared with macrophages from Xid mice. Experiments using cocultures of B-1 cells and macrophages from Xid mice in transwell plates demonstrated that B-1 cells down-regulate macrophage activities. These observations also indicate that this phenomenon is not due to a physical interaction between these two cell populations. As B-1 cells are one of the main sources of interleukin (IL)-10, we demonstrate in this study that adherent peritoneal cells from Xid mice produce significantly less amounts of this cytokine in culture when compared with IL-10 production by cells from wild-type mice. When B-1 cells from IL-10 knock-out mice and macrophages from wild-type mice were cocultured in transwell plates, the phagocytic index of macrophages was not altered demonstrating that B-1 cells can influence the effector functions of macrophages in vitro via IL-10 secretion.     

Human chromosome 16 conservation in primates

A study was made of the organization of the chromosome orthologous to HSA16 in primates using a panel of 8 BAC probes spanning human chromosome 16. The probes were used in FISH experiments on great apes and on representatives of the Old World monkeys, New World monkeys, and lemurs. The domestic cat was used as an outgroup. The results indicate that 16p and 16q were separate chromosomes in a primate ancestor. They fused in a Catarrhini ancestor giving rise to the present day form found in HSA, great apes, and Old World monkeys. Several rearrangements were found in New World monkeys.     

B-1 cells are pivotal for in vivo inflammatory giant cell formation

The mechanisms that govern giant cell (GC) formation in inflammatory, neoplastic and physiologic conditions are far from being understood. Here, we demonstrate that B-1 cells are essential for foreign-body GC formation in the mouse. GCs were analysed on the surface of glass cover slips implanted into the subcutaneous tissue of the animals. It was demonstrated that GCs are almost absent on cover slips implanted into the subcutaneous tissue of BALB/c or CBA/N X-linked immunodeficient mice. As these animals do not have B-1 cells in the peritoneal cavity, they were reconstituted with B-1 cells obtained from cultures of adherent mouse peritoneal cells. Results showed that in B-1-reconstituted animals, the number of GCs on the implant surface surpassed the values obtained with preparations from wild animals. In animals selectively irradiated (pleural and peritoneal cavities) to deplete these cavities of B-1 cells, GCs were also not formed. Enriched suspensions of B-1 cells grown in culture were labelled with [(3)H]-tymidine and injected into the peritoneal cavity of naive mice before implantation of glass cover slips. After 4 days, about 17% of mononuclear cells had their nuclei labelled, and almost 70% of GCs had one or more of their nuclei labelled when analysed by histoautoradiographic technique. A few GCs expressed an immunoglobulin M when analysed by immunostaining and confocal microscopy. Overall, these data demonstrate that B-1 cells are pivotal in the mechanisms of foreign-body GC formation in the mouse.     

Modulation of mechanosensory responses by motoneurons that regulate skin surface topology in the leech

Central regulation of somatosensory signals has been extensively studied, but little is known about their regulation in the periphery. Given the widespread exposure of the skin sensory terminals to the environment, it is of interest to explore how somatosensory sensitivity is affected by changes in properties of the skin. In the leech, the annuli that subdivide the skin can be erected under the control of the annulus erector (AE) motoneurons. To analyze whether this surface change influences mechanosensory sensitivity, we studied the responses of low threshold mechanosensory T cells to mechanical stimulation of the skin as AE motoneurons were activated. In segments of the body wall connected to the corresponding ganglion and submerged in an aqueous environment, T cells responded to localized bubbling on the skin and to water flow parallel to its surface. Excitation of AE motoneurons diminished these responses in a way that depended on the motoneuron firing frequency. Video recordings established that the range of AE firing frequencies that produced effective annulus erection coincided with that influencing T cell responses. In isolated ganglia, AE firing had no effect on T cell excitability, suggesting that annulus erection diminished T cell responsiveness to mechanical input. Counteracting this effect, mechanosensory inputs inhibited AE motoneurons. However, because depolarization of AE cells caused a decrease in their input resistance, the more active the motoneuron, the less sensitive it became to inhibitory signals. Thus when brought to fire, AE motoneurons would stay "committed" to a high activity level, and this would limit sensory responsiveness to incoming mechanical signals.     

The pattern of cardiovascular alterations induced by infusion of platelet-activating factor in rabbit is modified by pretreatment with H1-H2 receptor antagonists but not by cyclooxygenase inhibition

The intravenous infusion of platelet activating factor (PAF) (0.8 g/kg b.w.) induced ECG and hemodynamic alterations characterized by the following sequential three phases. Phase I (15 sec) consisted of a transient bradycardia with reduction in left ventricular pressure (LVPs), mean arterial pressure (MAP) and cardiac output (CO). Phase II developed within 30 sec and consisted of a rise in cardiac frequency, increase in LVPs, MAP and total peripheral resistances (TPR), which were associated with a decrease in CO. Finally, phase III, that occurred about 90 sec after PAF infusion, was characterized by marked ECG changes (ST segment depression and conduction arrhythmias), a decrease in LVPs and MAP, as well as a rise in TPR and in right atrial pressure (RAP). All these alterations were reversible within 30–60 min. Pretreatment with promethazine and cimetidine, as H₁ and H₂ histamine receptor antagonists, markedly prevented the development of phase II, namely the rise in cardiac frequency, LVPs, MAP and TPR, but did not significantly modify phase I and III. In contrast, pretreatment with indomethacin, an inhibitor of cyclooxygenase, moderatively attenuated, but did not abolish, the three phases of cardiovascular changes induced by PAF infusion.     

High-frequency reactivation of X-linked genes in chinese hamster × human hybrid cells

Three genes on the human inactive X chromosome retained in the Chinese hamster x human hybrid cell line X8/6T2 have been reactivated using the demethylating agent, 5-azacytidine (5-aza-CR). Pulse-labeling and histochemical methods permitted detection and measurement of reactivation rates of the hypoxanthine phosphoribosyltransferase (Hpt) and glucose-6-phosphate dehydrogenase (G6pd) genes within 48 h of treatment. About 50% of the cells became active for these genes, which represents a reactivation rate some 30-fold greater than previously reported in similar systems. The phosphoglycerate kinase (Pgk) gene was not reactivated as frequently as the Hptor G6pdgenes. Segregation analysis of progeny of treated cells showed that enzyme-positive and enzyme-negative cells were produced in proportions supporting the notion that 5-aza-CR causes demethylation by replicative loss and that demethylation leads to reactivation.     

Efficacy of human recombinant erythropoietin plus IFN-alpha in patients affected by chronic hepatitis C.

Determination of serum iron levels in patients affected by chronic hepatitis C is considered fundamental for studying the response to interferon-alpha (IFN-alpha) treatment. IFN could induce anemia, which is promptly corrected by exogenous administration of recombinant human erythropoietin (rHuEPO). The aim of our study was to verify the possible beneficial effect of rHuEPO in patients affected by chronic hepatitis C and treated with IFN. Seventy consecutive patients (42 males and 28 females, mean age 46.4+/-5.2 years) affected by chronic hepatitis C were enrolled. In all patients, chronic hepatitis C was diagnosed on the basis of clinical and biological findings (alanine aminotransferase [ALT] serum levels at least 2-fold higher than normal values for at least 12 months and the presence of anti-HCV antibodies). All patients were negative for hepatitis B virus (HBV) infection, hepatitis D virus (HDV infection, and HIV infection. Statistical analysis was carried out using the Wilcoxon nonparametric sum rank test, the Spearman correlation rank test, and the Friedman ANOVA and Kendall coefficient of concordance. At the end of the treatment, our study series showed significant differences in serum levels of AST (p < 0.001), iron (p < 0.001), and ferritin (p < 0.001). At the end of the follow-up period, significant differences were seen in ALT, aspartate (AST), and iron ferritin and transferrin levels. All differences favored patients who received IFN-alpha and rHuEPO. We think that the depletion of circulating iron may improve the immune response impaired by iron accumulation in the liver. Our study confirms the important role played by iron in the response to IFN treatment, suggesting that the use of rHuEPO induces a better response to IFN in patients with chronic hepatitis C by activation of erythropoiesis.     

IL-10 stimulates production of platelet-activating factor by monocytes of patients with active systemic lupus erythematosus (SLE)

IL-10 displays modulatory properties on the synthesis of platelet-activating factor (PAF), a potent inflammatory mediator of vascular injury. Despite the fact that IL-10 is considered to be an anti-inflammatory cytokine, IL-10 levels correlate with disease activity in SLE. Moreover, in SLE IL-10 is unable to exert its immunosuppressive and anti-inflammatory effects. We have investigated the ability of IL-10 to stimulate PAF production from monocytes of SLE patients. Spontaneous and IL-10-stimulated PAF production by peripheral blood monocytes was measured in active (n = 13) and inactive (n = 14) SLE patients and in 15 normal control subjects. We observed that monocytes derived from patients with active SLE, but not from controls or inactive SLE, spontaneously produced significant amounts of PAF. Moreover, IL-10 enhanced the synthesis of PAF from monocytes of active SLE patients only. IL-10-induced PAF production correlated with the severity of the disease and with the extent of proteinuria. These results indicate that IL-10 only stimulates the synthesis of PAF from monocytes of SLE patients when immunologically active, suggesting that IL-10 may possess a paradoxical proinflammatory effect in SLE by promoting the production of PAF, a secondary mediator of inflammation.     

Invasion profiles of Brazilian field isolates of Plasmodium falciparum: phenotypic and genotypic analyses

The invasion of red blood cells (RBCs) by Plasmodium falciparum is dependent on multiple molecular interactions between erythrocyte receptors and parasite ligands. Invasion studies using culture-adapted parasite strains have indicated significant receptor heterogeneity. It is not known whether this heterogeneity reflects the parasite invasion arsenal in the field. We have studied the invasion phenotypes of 14 distinct field isolates from the Legal Amazon areas of Brazil by using erythrocyte invasion assays to investigate invasion into normal, enzyme-treated, and clinical-mutant RBCs. Analysis of these isolates revealed four distinct invasion profiles. Using En(a-) cells to get an unequivocal estimate of the use of glycophorin A (GPA) as a receptor, we found that the 175-kDa erythrocyte-binding antigen (EBA-175)/GPA pathway was used by a minority of the parasite isolates studied. Although polymorphism of region II domains at specific amino acid positions in both EBA-140 and EBA-181 was found in these field isolates, this did not correlate with invasion profiles and thus receptor selectivity. These studies have further confirmed the existence of a significant diversity of invasion pathways in nature and suggest that additional parasite ligands will have to be targeted to devise global vaccines that will work in the field.