Beryllium presentation to CD4+ T cells underlies disease-susceptibility HLA-DP alleles in chronic beryllium disease

Chronic beryllium disease results from beryllium exposure in the workplace and is characterized by CD4(+) T cell-mediated inflammation in the lung. Susceptibility to this disease is associated with particular HLA-DP alleles. We isolated beryllium-specific T cell lines from the lungs of affected patients. These CD4(+) T cell lines specifically responded to beryllium in culture in the presence of antigen-presenting cells that expressed class II MHC molecules HLA-DR, -DQ, and -DP. The response to beryllium was nearly completely and selectively blocked by mAb to HLA-DP. Additional studies showed that only certain HLA-DP alleles allowed presentation of beryllium. Overall, the DP alleles that presented beryllium to disease-specific T cell lines match those implicated in disease susceptibility, providing a mechanism for this association. Based on amino acid residues shared by these restricting and susceptibility DP alleles, our results provide insight into the residues of the DP beta-chain required for beryllium presentation.     

Peripheral vascular complications after intracoronary stent placement: Prevention by use of a pneumatic vascular compression device

Peripheral vascular complications are a significant source of morbidity after coronary artery stent implantation. The goal of this study was to assess the incidence, risk factors, and management of vascular complications after stent placement. The study population consisted of 101 consecutive patients who underwent stent placement for either elective or bailout indications. All patients received a standardized anticoagulation regimen of aspirin, dipyridamole, low molecular weight dextran, heparin, and warfarin. Peripheral vascular access sites were examined daily until hospital discharge. Vascular complications occurred in 16 of 101 (16%) patients, including femoral artery pseudoaneurysm (n = 11), hematoma requiring transfusion or surgery (n = 4), and arterlovenous fistula (n = 1). Intervention was required in 14 of 16 (88%) patients with complications. These included transfusion (n = 7), ultrasound-guided compression (n = 8), and/or vascular surgery (n = 7). Length of hospital stay was prolonged in patients with complications (14 ± 9 vs. 8 ± 5 d, P < 0.001). The development of peripheral vascular complications did not correlate with clinical or procedural variables such as age, cardiovascular risk factors, arterial sheath size, or elective vs. bailout indication. After the introduction of a pneumatic vascular compression device (FemoStop, C.A. Bard, Billerica, MA), a significant reduction In vascular complications was observed. Complications occurred in only 1 of 41 (2.4%) patients in whom the compression device was used in contrast to 13 of 58 (22.4%) patients compressed manually (P < 0.01). Thus peripheral vascular complications are frequent after coronary artery stent placement and are associated with serious morbidity and prolongation of hospital stay. These complications are significantly reduced by the use of a pneumatic vascular compression device despite intensive systemic anticoagulation. © 1996 Wiley-Liss, Inc.     

Nuclear magnetic resonance imaging of acute myocardial infarction in dogs: Alterations in magnetic relaxation times

Nuclear magnetic resonance (NMR) imaging was used to study 24-hour-old acute myocardial infarctions in 8 dogs. Images and measurements of excised hearts were obtained in a 6.5 ml bore-resistive NMR imager (0.35 Tesla). Spin echo NMR imaging in each instance demonstrated the area of infarction as a region of increased signal intensity compared with that in normal myocardium. The T1 and T2 values of the area of infarction were greater than those of normal myocardium in all dogs. For each dog the T1 value was greater for the infarct region; however, the group mean value for T1 (ms) of the infarct region (728 ± 94) was not significantly greater than that for the normal region (650 ± 87). The T2 value (ms) was discriminate for all dogs, and the mean value for the infarct region (48 ± 2) was significantly different (p < 0.01) from the value for normal myocardium (42 ±1). The percent water content of the infarct (79 ± 1%) was significantly greater (p < 0.01) than that of normal regions (76 ± 1 %). The linear relationship between T2 value and percent water content showed a good correlation coefficient (r = 0.90; p < 0.01).NMR imaging detects acute myocardial infarction as a positive image without contrast media. Increased signal intensity of the infarct is related to increased hydrogen density and increased T2 relaxation time.     

Regulation of insulin and glucagon secretion from a human islet cell adenoma.

The regulation of insulin biosynthesis, and insulin and glucagon secretion have been investigated in a human islet cell adenoma, by incubation of tumour fragments. Both biosynthesis and secretion of insulin were strongly stimulated by incubation of islet tumour cells in the presence of increasing glucose concentrations in the range 2-8 mmol/1. However, 20 mM-glucose or 20 mM-glucose plus isobutyl methylxanthine (IBMX), both of which provide potent secretagogues for normal B cells, failed to stimulate proinsulin biosynthesis and secretion from the tumour cells. Overall rates of secretion, expressed as a proportion of total insulin content, were up to 20-fold higher than those expected for normal pancreatic tissue. Glucagon secretion from the tumour was stimulated by low glucose concentrations; normal A cells also respond in this way under these conditions. However, no stimulation of glucagon secretion occurred in the presence of IBMX. There was therefore a major alteration in the regulation both of insulin and glucagon secretion, in that release of neither hormone was stimulated by cyclic AMP. Ultrastructural examination showed the tumour to be rather heterogeneous. A and B cells with normal storage granule content and structure were seen, as well as a rather larger number of B cells containing some granules of atypical appearance. The insulin content of the tumour (13 i.u./g wet wt) was consistent with 6-8% of the tumour cells being B cells.     

Cellular Fluid Mechanics and Mechanotransduction

Mechanotransduction, the transformation of an applied mechanical force into a cellular biomolecular response, is briefly reviewed focusing on fluid shear stress and endothelial cells. Particular emphasis is placed on recent studies of the surface proteoglycan layer (glycocalyx) as a primary sensor of fluid shear stress that can transmit force to apical structures such as the plasma membrane or the actin cortical web where transduction can take place or to more remote regions of the cell such as intercellular junctions and basal adhesion plaques where transduction can also occur. All of these possibilities are reviewed from an integrated perspective.     

Corticotropin releasing factor 2 receptor agonists reduce the denervation-induced loss of rat skeletal muscle mass and force and increase non-atrophying skeletal muscle mass and force

Of the two corticotropin releasing factor receptors known, corticotrophin releasing factor 2 receptor (CRF2R) is expressed in skeletal muscle. The function of this receptor in skeletal muscle is at present unknown. In order to better understand the role of the CRF2R in skeletal muscle, we treated rats with CRF2R agonists and evaluated the effect of these agents on normal and denervated muscle mass. Rats treated with the non-selective CRFR agonist, sauvagine, did not demonstrate any significant and consistent change in non-denervated and denervated fast twitch [tibialis anterior (TA) or extensor digitorum longus (EDL)] or slow/mixed twitch [medial gastrocnemius (MG) or soleus] fiber muscle mass. In adrenalectomized rats, sauvagine treatment resulted in no significant and consistent change in non-denervated fast or slow/mixed twitch fiber muscles but did cause a significant and consistent increase in denervated fast twitch (TA and EDL) but not slow/mixed twitch muscle mass. Interestingly adrenalectomy had no effect on the degree of muscle atrophy. Rats treated with the CRF2R selective agonist urocortin 2 demonstrated an increase in non-denervated and denervated fast and slow/mix twitch fiber muscle mass. The urocortin 2 induced increase in muscle mass was accompanied by an increase in muscle fiber cross-sectional area and muscle absolute force. These studies demonstrated that activation of the CRF2R decreased the level of skeletal muscle mass, force, and myocyte cross-sectional area loss resulting from sciatic nerve damage and increased the mass, force and myocyte cross-sectional area of normal (non-atrophying) skeletal muscle. In addition, we also observed that removal of the adrenals increased the effectiveness of the non-selective CRFR agonists sauvagine, presumably via the removal of the pro-atrophy influence of adrenal produced corticosteroids. These results demonstrate that pharmacological modulation of the CRF2R may be a viable method to treat skeletal muscle atrophy.     

Immunization with a DNA vaccine cocktail protects mice lacking CD4 cells against an aerogenic infection with Mycobacterium tuberculosis

Tuberculosis (TB) is the most common opportunistic disease and a potentially fatal complication among immunocompromised individuals infected with human immunodeficiency virus (HIV). Effective vaccination against TB in persons with HIV has been considered unlikely because of the central role that CD4 cells play in controlling tuberculous infections. Here we show that the vaccination of CD8^−/− mice with a TB DNA vaccine cocktail did not significantly enhance protective responses to a Mycobacterium tuberculosis infection. In contrast, immunization with a DNA vaccine cocktail or with the current TB vaccine, Mycobacterium bovis BCG, induced considerable antituberculosis protective immunity in immune-deficient mice lacking CD4 cells. In vaccinated CD4^−/− animals, substantially reduced bacterial burdens in organs and much improved lung pathology were seen 1 month after an aerogenic M. tuberculosis challenge. Importantly, the postchallenge mean times to death of vaccinated CD4^−/− mice were significantly extended (mean with DNA cocktail, 172 ± 7 days; mean with BCG, 156 ± 22 days) compared to that of naïve CD4^−/− mice (33 ± 6 days). Furthermore, the treatment of DNA-vaccinated CD4^−/− mice with an anti-CD8 or anti-gamma interferon (IFN-γ) antibody significantly reduced the effect of immunization, and neither IFN-γ^−/− nor tumor necrosis factor receptor-deficient mice were protected by DNA immunization; therefore, the primary vaccine-induced protective mechanism in these immune-deficient mice likely involves the secretion of cytokines from activated CD8 cells. The substantial CD8-mediated protective immunity that was generated in the absence of CD4 cells suggests that it may be possible to develop effective TB vaccines for use in HIV-infected populations.Tuberculosis (TB) remains a significant global threat to public health, with two million people dying from Mycobacterium tuberculosis infections each year and eight million cases of TB developing annually (6). The increasing linkage of TB with the human immunodeficiency virus (HIV) pandemic has magnified this tragedy in the past decade. The World Health Organization estimates that at least six million people worldwide are coinfected with M. tuberculosis and HIV (18). The HIV-M. tuberculosis coinfection rates exceed 5% in eight African countries, and in South Africa alone two million adults are coinfected (9). In these developing countries, TB is the most prevalent cause of morbidity and mortality for HIV-positive adults. In contrast to immunocompetent individuals, who have a 10% lifetime risk of disease following TB infection, persons coinfected with M. tuberculosis and HIV have a nearly 10% annual risk of developing disease.A primary reason for the continued failure to curb the global TB epidemic is the absence of a highly effective vaccine. Although the current TB vaccine, Mycobacterium bovis BCG, has been widely used for decades, its efficacy in controlled clinical trials has been extremely variable and its value in protecting against the most prevalent form of the disease, adult pulmonary TB, is doubtful (7). Moreover, the effectiveness of BCG in preventing TB in HIV-infected individuals is uncertain. Since BCG is a live vaccine (attenuated but not avirulent) and since clinical cases of reactivated BCG have been reported for HIV-infected persons, BCG vaccination has not been indicated for immunocompromised individuals (33).The development of a new vaccine against TB for use in HIV-positive persons has been considered unlikely because of the presumed essential roles that CD4 cells play in controlling TB infections. Mice that lack CD4 cells or that are aberrant in major histocompatibility complex class II presentation are extremely sensitive to a TB challenge and cannot effectively control acute TB infections (3, 13). The greatly enhanced susceptibility of HIV patients to both primary and reactivated disease argues that CD4 cells also play a prominent role in protective immune responses against human TB. The primary antituberculosis effector function of CD4⁺ T cells involves the production and secretion of cytokines which activate macrophages to control or eliminate the intracellular bacilli (13). In addition to this more direct role of CD4 cells in limiting tuberculous infections, CD4 cells also assist in the development of primary CD8 T-cell responses (23). CD4 cells stimulate professional antigen-presenting cells (APCs) primarily via CD40-CD40 ligand interactions; these activated APCs efficiently costimulate antigen-specific naïve CD8 T cells. Additionally, cytokine production from CD4 cells enhances the proliferation of primed CD8 cells.Despite the critical immune functions of CD4 cells, recent studies have demonstrated that protective immunity to pathogens can be generated in the absence of CD4 cells. For instance, substantial CD8 T-cell responses to the influenza virus, lymphocytic choriomeningitis virus (LCMV), and pathogenic fungi can occur in mice lacking CD4 cells (17, 26, 34, 35). In a Listeria monocytogenes model, similar levels of activated CD8 T cells were detected in CD4^−/− and wild-type (WT) C57BL/6 mice after an infection. Importantly, the epitope-specific CD8 T cells that were generated established long-term memory in CD4^−/− mice and were capable of producing an effective recall response (21). Under circumstances in which CD4 help is not required for the generation of effective CD8 T-cell responses, alternate pathways for the activation of APCs exist. For influenza virus, a direct infection of dendritic cells results in the upregulation of costimulatory molecules. For bacteria, dendritic cells can be activated through recognition by Toll-like receptors (TLRs) of bacterial products such as peptidoglycan, glycolipids, and lipoproteins (2, 29, 30).Based on these findings in other immune-deficient disease models, we evaluated whether cell-mediated antituberculosis protective immunity could be induced in mice lacking CD4 cells by immunization with a DNA vaccine cocktail or with BCG. Previously, members of our laboratory generated a DNA cocktail that expressed mycobacterial proteins fused at the N terminus to ubiquitin (UB), a eukaryotic intracellular targeting sequence (10, 11). These UB-conjugated proteins were designed to enhance major histocompatibility complex class I presentation. In studies using WT C57BL/6 mice, it was shown that vaccination with this combination was more effective than immunization with the individual single components and that the sustained protective immunity induced by the plasmid mixture was equivalent to the level of protection elicited by the BCG vaccine (10, 11). We report here that substantial antituberculosis protective immunity can be induced in the absence of CD4 cells. Immunization of CD4^−/− mice with either the DNA vaccine cocktail or BCG leads to significantly decreased lung and spleen bacterial burdens and much improved lung pathology, relative to naïve controls, after an aerogenic M. tuberculosis infection. Most importantly, the survival of the vaccinated animals was substantially extended compared to nonimmunized CD4^−/− controls.     

Effectiveness of montelukast in the treatment of cough variant asthma.

BACKGROUND: Antileukotriene agents have been shown to be beneficial in chronic asthma. Although patients with cough variant asthma have cough with minimal wheezing and dyspnea, airway hyperresponsiveness from chronic inflammation is believed to be the underlying mechanism. OBJECTIVE: To evaluate the effectiveness of montelukast, a leukotriene receptor antagonist, in the treatment of cough variant asthma. METHODS: Fourteen patients with cough variant asthma participated in a randomized, double-blind, placebo-controlled trial with a 7- to 10-day baseline period and a 4-week treatment period with montelukast, 10 mg, or placebo daily. Inclusion criteria were (1) chronic cough with a duration of at least 4 weeks with minimal or no wheezing or dyspnea and (2) forced expiratory volume in 1 second of 50% to 85% of predicted and reversibility of 12% with use of an inhaled beta-agonist or forced expiratory volume in 1 second greater than 85% and positive methacholine challenge results. Patients fulfilled the minimum criteria for cough frequency and symptom scores for randomization. RESULTS: Eight patients received montelukast and 6 received placebo. The primary efficacy variable, mean percentage change from baseline in cough frequency, was significantly improved by the second week, and by the fourth week the mean percentage change from baseline was 75.7% for the treatment group and 20.7% for the placebo group. CONCLUSIONS: The leukotriene receptor antagonist montelukast seems to be effective in the treatment of cough variant asthma. Larger studies are recommended to confirm this effect.