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Biomedical subjects

N J Roberts

Publications and source records attributed to N J Roberts.

At least 55 records · Page 3Linked to original sources
PubMed1989

Early identification and retrieval or deletion of human lymphocyte subpopulations responding to influenza virus or respiratory syncytial virus challenge.

Differences in immune responses of human mononuclear leukocytes (MNL) have been demonstrated following exposure in vitro to influenza virus or respiratory syncytial virus (RSV). In the current studies, we sought to identify early differences in reactive subpopulations that emerge from within the heterogeneous resting MNL pool after challenge. MNL were sham-exposed or exposed to influenza virus or RSV, separated, and retrieved by countercurrent centrifugal elutriation after 3 d. Exposure to influenza virus caused a relative decline in the number of large MNL, but an increase in small lymphocytes. Large cells that remained included primitive lymphoblasts, rare plasma cells, and typical lymphocytes of progressively greater volume. Exposure to RSV increased the number of large MNL, but diminished the number of small lymphocytes. The subpopulation of large cells consisted of atypical and large granular lymphocytes. Furthermore, deletion of the latter large, reactive lymphocytes led to abrogation of an RSV-specific proliferative response upon subsequent challenge. Thus, the specific and different subpopulations reactive after infectious virus challenge could be identified, retrieved, and manipulated without dependence on a priori, phenotypic markers.

Adult↗
PubMed1989

Nitrogen dioxide exposure in vivo and human alveolar macrophage inactivation of influenza virus in vitro.

Epidemiologic studies have reported an increased incidence of respiratory infections and illness in association with elevated indoor levels of nitrogen dioxide (NO2). Animal exposure studies have found that brief exposures to peak levels of NO2 produce greater morbidity than continuous lower level exposure. In order to examine the effect of NO2 inhalation on human alveolar macrophages, normal volunteers were exposed sequentially to air or NO2, by double-blind randomization, in an environmental chamber. Two exposure protocols with comparable concentration x time products were used: (a) continuous 0.60 ppm NO2 (n = 9), and (b) background 0.05 ppm NO2 with three 15-min peaks of 2.0 ppm (n = 15). Inhalation of NO2 caused no significant changes in pulmonary function or airway reactivity in either exposure protocol. Alveolar macrophages obtained by bronchoalveolar lavage 3 1/2 hr after exposure to continuous 0.60 ppm NO2 tended to inactivate influenza virus in vitro less effectively than cells collected after air exposure (1.96 vs 1.25 log10 plaque-forming units on Day 2 of incubation, P less than 0.07). Four of nine subjects accounted for the observed impairment in virus inactivation; cells from these four subjects demonstrated an increase in interleukin-1 (IL-1) production after NO2 vs air, whereas the five remaining subjects decreased IL-1 production after NO2. In contrast, intermittent peak exposure did not alter the rate of viral inactivation or IL-1 production. This methodology has the potential to identify pollutant effects on mechanisms of respiratory defense in humans.

Adult↗
PubMed1989

Effects of nitrogen dioxide exposure on bronchoalveolar lavage proteins in humans.

Nitrogen dioxide (NO2) is a pollutant of both outdoor and indoor atmospheres that has the potential to alter alveolar epithelial permeability. In order to assess alterations in the protein content of alveolar lining fluid induced by brief (3-h) exposures to low-level NO2, normal volunteers were exposed sequentially to air and NO2, separated by at least 2 wk, in an environmental chamber. Bronchoalveolar lavage (BAL) was performed after exposure. Four experimental protocols were used: (1) continuous 0.60 ppm NO2 with BAL performed 3.5 h after exposure (n = 8), (2) background 0.05 ppm NO2 with three 15-min peaks of 2.0 ppm followed by BAL 3.5 h after exposure (n = 15), (3) continuous 0.60 ppm NO2 with BAL performed 18 h after exposure (n = 8), and (4) continuous 1.5 ppm NO2 with BAL 3.5 h after exposure (n = 15). No changes in lavage fluid levels of total protein or albumin were observed in response to NO2. However, exposure to continuous 0.60 ppm NO2 was associated with increases in lavage fluid levels of the antiprotease alpha-2-macroglobulin (alpha 2M) when assessed 3.5 h after exposure (air versus NO2: 20 +/- 1 versus 29 +/- 2 ng/ml, P = 0.01). No significant changes in levels of alpha 2M in BAL fluid were observed in the other exposure protocols. Lavaged cell numbers, differential counts, and viability were not altered by exposure to the pollutant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Effects of in vitro exposure to nitrogen dioxide on human alveolar macrophage release of neutrophil chemotactic factor and interleukin-1.

To evaluate the potential toxic and immunologic effects of nitrogen dioxide (NO2) exposure on cells from the lower respiratory tract, normal human alveolar macrophages obtained by bronchoalveolar lavage were exposed to increasing concentrations of NO2 using an in vitro exposure system. Alveolar macrophages exposed to 5, 10, or 15 ppm NO2 for 3 hr showed no difference in cell viability when compared to air-exposed macrophages. In addition, the spontaneous release of neutrophil chemotactic factor (NCF) was not changed by NO2 exposure, nor was there any effect on the ability of alveolar macrophages to release increased amounts of NCF following stimulation with activated zymosan. Furthermore, alveolar macrophages did not spontaneously release interleukin-1 (IL-1) following air or NO2 exposure. When stimulated with influenza virus both air- and NO2-exposed cells released increased amount of IL-1, but was no significant difference in the amount of IL-1 released by air- and NO2-exposed alveolar macrophages. Thus, although NO2 exposure is known to incite an inflammatory response in the lower respiratory tract, using the in vitro exposure system described in this study we were unable to demonstrate a direct toxic effect of NO2 on viability or any NO2-induced change in the release of the immunoregulatory molecules NCF and IL-1.

Adult↗
PubMed1988

Influenza virus infection of tracheal gland cells in culture.

Influenza virus-induced tracheobronchitis causes limited epithelial deciliation but markedly decreased mucociliary transport. This suggests that virus-induced alterations in airway mucus play a role in decreased mucociliary transport. Airway submucosal glands are a primary source of mucus. Therefore, we examined virus-gland cell interactions by exposing primary cultures of isolated feline tracheal gland cells to influenza A/Scotland/840/74 H3N2 virus for 1 h at a multiplicity of infection of 0.1. Virus production and release into the culture medium first occurred between 8 and 12 h postinfection and eventually reached a steady state that continued for at least 8 days. Virus which was produced and released by infected cells infected other monolayers, resulting in viral production similar to that after infection with stock virus. Hemadsorption assays conducted 24 h after infection demonstrated that most of the cells in a monolayer became infected. The infection was nonlytic according to cell morphology, trypan blue dye exclusion, and release of lactate dehydrogenase. Because lysis of a cell subpopulation could have been masked by subsequent cell division, we compared the uptake of [3H]thymidine by infected and control monolayers. There was no increase in uptake by infected monolayers. These results demonstrate that feline tracheal gland cells in primary culture undergo productive and nonlytic infection with influenza A virus. This model provides a unique system for the study of virus-gland interactions isolated from the influence of other tissues.

Animals↗
PubMed1988

Human alveolar macrophage suppression of lymphocyte proliferation. Accessory characteristics for the generation and functional expression of con A-induced suppressor cells.

Human alveolar macrophages (AM) provide less accessory support for mitogen- and antigen-stimulated lymphocyte proliferation than do autologous blood-derived macrophages (BM). This is at least in part due to suppression mediated by AM, but the mechanism of such suppression is not understood. To determine whether AM-mediated suppression is related to AM interaction with suppressor lymphocytes (Ts), we examined the accessory cell function of both AM and BM for the generation and functional expression of Ts induced by concanavalin A (Con A). The data indicate that human AM are equivalent to BM for the generation of Con A-induced Ts, but AM mediate less suppression of Con A-induced Ts, once generated, than do BM. Addition of indomethacin did not increase lymphocyte proliferation when AM served as accessory cells. Supernatant fluids of Con A-exposed AM promoted greater proliferation of human T-lymphocytes and mouse thymocytes than did supernatant fluids from Con A-exposed BM. Interleukin-1 inhibitor activity was not detected in the supernatant fluids. These observations make it unlikely that soluble factors alone account for AM-mediated suppression. Thus, at least for the Con A-induced Ts system, AM do not mediate suppression either via better generation or greater functional expression of suppressor cells relative to BM. The paradoxically greater proliferation of lymphocytes stimulated by the supernatant fluids of Con A-exposed AM raises the possibility that suppression of Con A-stimulated lymphocyte proliferation observed when AM serve as the accessory cells in primary culture may be related to AM secretion of a molecule with IL-1-like activity.

Adult↗
PubMed1987

Macrophages are required for influenza virus infection of human lymphocytes.

Monocyte and lymphocyte surface-expressed viral antigens have been demonstrated after exposure of unseparated human mononuclear leukocytes to influenza virus in vitro. The current studies, using [35S]methionine pulse-labeled purified preparations of virus-exposed macrophages, depleted of lymphocytes, demonstrate that the presence of these viral proteins does represent new synthesis. However, purified lymphocytes, depleted of monocytes-macrophages and exposed to influenza virus, showed no detectable viral protein synthesis. In further experiments, unseparated mononuclear leukocytes were exposed to virus and subsequently separated by countercurrent centrifugal elutriation. Both macrophages and lymphocytes were then shown to synthesize influenza proteins. Cell-free control or influenza virus-infected macrophage-derived supernatant fluids did not facilitate influenza virus infection of the lymphocytes. The data suggest that macrophages are required for influenza virus infection of human lymphocytes, and raise the possibility that macrophage facilitation of an abortive infection of lymphocytes plays a role in the generation of effective immunity to viral antigens.

Antigens, Viral↗
PubMed1987

Mitogen responsiveness after exposure of influenza virus-infected human mononuclear leukocytes to continuous or pulse-modulated radiofrequency radiation.

Data are available regarding interactions of radiofrequency radiation (RFR) with normal human mononuclear leukocytes. However, no data have emerged regarding effects of RFR on human leukocytes already challenged by a commonly encountered alternate agent, such as a virus. Therefore, in these studies, uninfected (control) and in vitro influenza virus-infected human mononuclear leukocytes were exposed to 2450 MHz RFR as continuous waves or pulse-modulated at 60 or 16 Hz, at a specific absorption rate of 4 mW/ml. Such exposures produced no significant effects on leukocyte viability or on mitogen-stimulated DNA synthesis by either uninfected or influenza virus-infected leukocytes when compared to sham-RFR-exposed of cells.

Humans↗
PubMed1986

Interleukin 1 and interleukin 1 inhibitor production by human macrophages exposed to influenza virus or respiratory syncytial virus. Respiratory syncytial virus is a potent inducer of inhibitor activity.

Respiratory viral infections are commonly associated with altered immune responses, such as proliferative responses to mitogens and antigens. To examine potential mechanisms, we examined production of IL-1 and IL-1 inhibitors by purified human peripheral blood-derived macrophages exposed to influenza virus or respiratory syncytial virus (RSV). IL-1 and IL-1 inhibitor activities in supernatant fluids from macrophages exposed to the viruses 24 h previously were measured using the standard mouse thymocyte comitogen assay. Crude fluids from macrophages exposed to influenza virus contained substantial IL-1 activity, whereas crude fluids from macrophages exposed to RSV contained marked IL-1 inhibitor activity. Assays with gel filtration-separated fractions revealed that both influenza virus and RSV induced production of both IL-1 and IL-1 inhibitors. Neither IL-2 nor IL-2 inhibitor activities were detected. Thus, effects of human macrophage-derived factors on thymocyte proliferation, or potentially on human lymphocyte proliferation, may reflect the total or net activity of multiple composite factors, the balance of which varies according to the challenge. The data raise the possibility that marked production of IL-1 inhibitor activity in response to RSV plays a role in the clinical recurrence of RSV infection despite the absence of clear evidence for antigenic shift or drift of the virus.

Humans↗
PubMed1986

The biological effects of radiofrequency radiation: a critical review and recommendations.

Exposure of the general public and in particular certain occupational groups to radiofrequency radiation (RFR) is ubiquitous and of growing concern. No clear and widely accepted understanding of the biological effects and health implications of such RFR exposure has emerged. This paper reviews the data available, including reports of RFR effects on single cells or cell components, on genetic composition or development, on developed organs, tissues, or cell systems, and on integrative and regulatory biological systems. Reports of RFR effects on the immunological system, with consideration of the influence of neuroendocrine responses, are critically reviewed in greater detail to illustrate important points regarding data acquisition and assessment, and understanding and application of the RFR bioeffects literature in general. Factors affecting RFR bioeffects research are reviewed, and recommendations for future studies are provided.

Abnormalities, Radiation-Induced↗
PubMed1986

Human alveolar macrophage regulation of lymphocyte proliferation.

Human alveolar macrophages obtained by bronchoalveolar lavage have different accessory cell characteristics than do autologous, peripheral-blood-derived macrophages for the support of lymphocyte proliferative responses. To further investigate these differences, we performed mixing experiments in which variable numbers of the 2 macrophages were cocultured and assayed for support of mitogen-(phytohemagglutinin; PHA) and antigen-(streptokinase-streptodornase; SK-SD) stimulated proliferation of purified autologous lymphocytes. Alveolar macrophages promoted greater lymphocyte proliferation, in proportion to their added number in coculture with peripheral-blood-derived macrophages, when using a suboptimal concentration of PHA. In contrast, even small numbers of alveolar macrophages suppressed lymphocyte proliferation supported by peripheral-blood-derived macrophages when using the optimal concentration of PHA or the antigen SK-SD. The data indicated that diminished support exhibited by alveolar macrophages for optimal mitogen-stimulated or antigen-stimulated lymphocyte responses was due to active suppression by the cells, rather than to deficient or defective accessory cell function. Thus, alveolar macrophages have regulatory effects on lymphocyte proliferation that are dependent on type and concentration of mitogenic stimulation. Such regulation may relate to alveolar macrophage function in vivo, providing appropriate response yet limiting inflammation in the lung.

Adult↗
PubMed1986

Differential effects of hyperthermia on human leukocyte production of interferon-alpha and interferon-gamma.

Hyperthermia is being used clinically in the treatment of neoplasms. However, there are insufficient data regarding effects of hyperthermia on leukocyte functions potentially important in antitumor immunity. In order to provide such data, human mononuclear leukocytes were exposed to moderate (40.7 degrees C) and marked (42.7 degrees C) hyperthermia for 2 hr. Leukocyte viability, measured by dye exclusion, was not altered by such exposures. Exposure of the cells to moderate hyperthermia did not alter leukocyte production of interferon-alpha in response to influenza virus or interferon-gamma in response to the mitogen phytohemagglutinin. Exposure of the cells to marked hyperthermia significantly depressed production of interferon-alpha. In contrast, production of interferon-gamma was not altered by exposure of the leukocytes to marked hyperthermia. Many studies support a role for interferons (alpha as well as gamma) in antitumor immunity. The current and other data suggest that marked hyperthermia in cancer therapy should be applied locally whenever possible, rather than to the whole body, in order to limit adverse effects on immunity. The data suggest further that interferon-gamma may be a heat shock (stress) protein for human leukocytes.

Adult↗
PubMed1985

Epidemiological studies of human exposures to radiofrequency radiation. A critical review.

The health effects to exposure to radiofrequency radiation (RFR) remain undefined and controversial. Epidemiological studies of human exposures to RFR are confounded by difficulties in determining the type and true extent of exposures, in selecting an appropriate control group for comparisons, in determining the existence and influence of many concomitant environmental factors, and in establishing the presence or measuring the frequency or severity of subjective complaints was well as objective findings in the studied populations. This paper reviews reported RFR effects on general health, growth and development, physiological systems such as the cardiovascular and nervous systems, and organs such as the eye. Criteria for reliable epidemiological studies are presented to allow critical analysis of such reports.

Abnormalities, Radiation-Induced↗
PubMed1985

Expression of viral antigens after infection of human lymphocytes, monocytes, and macrophages with influenza virus.

Previous studies demonstrated that in vitro infection with influenza A viruses altered several functions of human monocytes and macrophages, but did not detectably alter functions of human lymphocytes. For a determination of whether both types of leukocytes can be infected by the influenza viruses, human mononuclear leukocytes were infected in vitro and assayed for newly produced and cell surface-expressed viral antigens, with use of indirect immunofluorescence techniques and flow cytometry. Infected cells, including both monocytes and lymphocytes, expressed viral hemagglutinin, neuraminidase, and matrix protein on their surfaces. The expression of influenza virus antigens by such immunocompetent cells may be important in human antiviral defense.

Antigens, Viral↗
PubMed1985

Respiratory syncytial virus infection of human mononuclear leukocytes in vitro and in vivo.

Recurrent infections with respiratory syncytial virus (RSV) have been well documented despite serological evidence of prior exposure of the host and the absence of clear evidence of antigenic variation of the virus. Therefore, human mononuclear leukocytes, as well as purified lymphocytes and monocytes-macrophages, were exposed to RSV in vitro and examined for expression of viral antigens by using indirect immunofluorescence with monoclonal antibodies to RSV. RSV infected both human monocytes-macrophages and lymphocytes in vitro. RSV infection resulted in both a decrease in the number of T helper phenotype cells and an increase in T suppressor phenotype cells. RSV proteins were disproportionately expressed by atypical or lymphoblastoid cells, many of which were of the T suppressor phenotype. Circulating mononuclear leukocytes obtained from symptomatic children infected with RSV frequently expressed viral antigens. Viral antigens appeared to be detected more frequently in cells from the younger subjects. The findings suggest that initial or early RSV infections in children include infection of circulating immunocompetent cells. It remains to be determined whether the described RSV-induced alterations in lymphocyte subpopulations contribute to recovery from and/or recurrence of RSV infections.

Adult↗
PubMed1985

Hemadsorption focus assay for growth of influenza and parainfluenza viruses in human dermal fibroblasts.

An assay for virus-induced hemadsorption foci in cultures of human dermal fibroblasts is described. The assay allows determination of activity of species-specific as well as nonspecific antiviral agents or biological factors, such as interferons. The assay may be used for abortive (e.g., influenza virus) and productive (e.g., parainfluenza virus) infections of human fibroblasts.

Fibroblasts↗
PubMed1985

Hyperthermia and human leukocyte functions: DNA, RNA, and total protein synthesis after exposure to less than 41 degrees or greater than 42.5 degrees hyperthermia.

Hyperthermia is being used clinically in the treatment of neoplasms, and mononuclear leukocytes are commonly present in a heated tumor or in surrounding tissues. Therefore, we examined the effects of exposure of human mononuclear leukocytes to less than 41 degrees or greater than 42.5 degrees hyperthermia for 2 h. The ability of the cells to exclude dyes, used as a measurement of leukocyte viability, was not altered by such exposures. Exposure of the cells to less than 41 degrees hyperthermia generally did not alter unstimulated or mitogen-stimulated DNA, RNA, or total protein synthesis. In contrast, exposure to greater than 42.5 degrees hyperthermia resulted in decreased unstimulated RNA and total protein synthesis, as well as delayed synthesis of DNA, RNA, and total protein in response to stimulation with the optimal concentration of mitogen and decreased synthesis in response to suboptimal concentrations of mitogen.

Adult↗