Biomedical subjects

C Steinmüller

Publications and source records attributed to C Steinmüller.

13 recordsLinked to original sources

PubMed2000

Local activation of nonspecific defense against a respiratory model infection by application of interferon-gamma: comparison between rat alveolar and interstitial lung macrophages.

Pulmonary macrophages play a crucial role in the defense of inhaled pathogens. We characterized functional properties of alveolar (AM) and interstitial (IM) macrophages from rats. AM exhibited a pronounced microbicidal capacity as shown by an elevated production of reactive oxygen intermediates (ROI), nitric oxide (NO), tumor necrosis factor (TNF)-alpha, and tumor cytotoxicity when compared with IM. In contrast, IM were superior to AM regarding mechanisms mainly involved in the induction and maintenance of specific immune reactions (major histocompatibility complex [MHC] class II expression, interleukin [IL]-1 and IL-6). In this line, we were interested in whether the microbicidal potential of AM could be augmented by treating Lewis rats with rat recombinant interferon (IFN)-gamma (5 x 10(2) to 1 x 10(5) U/animal) intratracheally, avoiding infection of interstitial lung macrophages or other organ-associated macrophages. The pulmonary cytokine application resulted in an activation of AM when macrophages from IFN-treated animals were compared with control macrophages from saline-treated rats 18 h after the treatment: (1) mediator release (ROI, NO, TNF-alpha, IL-6), (2) tumoricidal activity; (3) dose-dependent increase of MHC class II expression. The local immunomodulation enhanced the resistance of normal and immunosuppressed rats against respiratory infections with Listeria monocytogenes. Taken together, local activation of lung macrophages is a feasible therapeutic strategy against pulmonary infections.

Administration, Inhalation↗

PubMed1998

Behaviorally conditioned immunosuppression using cyclosporine A: central nervous system reduces IL-2 production via splenic innervation.

Bi-directional interactions between the central nervous system (CNS) and immune system are demonstrated by the modification of immune function using behavioral conditioning. However, the mechanisms by which the CNS achieves conditioned immunomodulation are still in question. Here, we report that the immunosuppressive effects of cyclosporine A (CsA) can be behaviorally conditioned in rats using saccharin as a gustatory conditioned stimulus. The conditioned effects were compared to control groups that received CsA paired with water (sham-conditioned), CsA injection on test days (CsA-treated), and unhandled rats (untreated). In conditioned animals, the mitogen-induced lymphocyte proliferation in the spleen is significantly suppressed, and the survival time of heterotopic heart allografts prolonged. These effects are paralleled by conditioned inhibition of IL-2 and IFN-gamma synthesis by splenocytes. Furthermore, the CNS-induced immunosuppression is mediated neuronally and not via the blood, since the conditioned reduction of proliferation and cytokine production is completely abrogated after surgical denervation of the spleen. Thus, during conditioning, the CNS learns to reinstate at demand a CsA-like immunosuppression via splenic innervation. This might be used as a supportive therapy for controlling immune functions.

Animals↗

PubMed1997

Analysis of leukocyte activation during acute rejection of pulmonary allografts in noninfected and cytomegalovirus-infected rats.

After human lung transplantation acute rejection and cytomegalovirus (CMV) infections may occur, probably contributing to the development of chronic rejection. We established a model of subacute allograft rejection in rats to analyze leukocyte activation and effects of a CMV infection. Histoincompatible lung transplants (BN/LEW) without immunosuppression (group A) and lungs of initially immunosuppressed animals (group B) were analyzed. The production of inflammatory mediators (interleukin-6, tumor necrosis factor alpha, nitric oxides) and the expression of MHC class II antigens by alveolar and lung tissue macrophages were significantly enhanced during the alloresponse. In recipients without immunosuppression (group A) allograft necrosis was detected by day 6, whereas group B allografts were fully rejected by day 25. In allografts of immunosuppressed, CMV-infected animals (group C) the CMV infection was clearly aggravated and the number of activated lung tissue macrophages was increased when compared with noninfected allografts or isografts. The subacute model provides the advantage of allowing us to study mechanisms of acute rejection without the effects of reperfusion injury. Furthermore these findings underline the role of inflammatory mediators produced by macrophages during rejection.

Acute Disease↗

PubMed1996

Characterization of murine lung interstitial macrophages in comparison with alveolar macrophages in vitro.

The present study was performed to characterize the immunologic potential of interstitial macrophages (INT) in comparison with alveolar macrophages (AL). The data showed that AL, compared with INT, have a more efficient phagocytic potential. In addition, they have a strong microbicidal activity and secrete large amounts of reactive oxygen radicals, nitric oxides, TNF, and IFN on appropriate stimulation. They also exert strong tumoricidal and parasiticidal activities. In contrast, INT are more efficient in releasing immunoregulatory cytokines such as IL-1 and IL-6. As determined by Ab staining, INT express more MHC class II molecules and are more effective in functioning as accessory cells for mitogen-stimulated lymphocyte proliferation compared with AL. Thus, AL appear to be particularly effective as nonspecific first line defense cells against infectious agents, whereas INT are equipped to cooperate with interstitial lymphocytes in inducing a specific immune reaction.

Animals↗

PubMed1996

Enhancement of cytomegalovirus infection and acute rejection after allogeneic lung transplantation in the rat: virus-induced expression of major histocompatibility complex class II antigens.

BACKGROUND: Cytomegalovirus infection is considered a major complication after lung and heart-lung transplantation because it can trigger acute and chronic rejection. The potential mechanisms of lung transplant rejection induced by viral infection include the upregulation of expression of major histocompatibility complex antigens. To address this question, a model of rat cytomegalovirus infection and acute lung transplant rejection was established. METHODS: Lewis inbred strain rats received syngeneic (n = 25) or allogeneic (Brown-Norway inbred rat strain, n = 38) orthotopic left-side lung transplants. Triple-drug immunosuppression with cyclosporin A, methylprednisolone, and azathioprine was given from postoperative days 1 through 10. Rat cytomegalovirus was inoculated intraperitoneally on postoperative day 3. Two control groups, those infected with cytomegalovirus (n = 15) and those without rat cytomegalovirus infection (n = 6) were treated with identical immunosuppressive regimens. Animals were sacrificed on postoperative days 11, 15, 18, 20, and 25. The salivary glands and both lungs were removed for pathologic and immunohistochemical investigations. RESULTS: All animals inoculated with rat cytomegalovirus developed systemic viral infection on or after postoperative day 11, as confirmed by an assay of plaque-forming units and immunohistologic examination. Cytomegalovirus-induced expression of major histocompatibility complex class II antigens on vascular endothelial cells was seen in the nontransplanted lungs of rats, but no major histocompatibility complex class II antigens were detected on noninfected, nontransplanted lungs. Cytomegalovirus infection also was found to enhance major histocompatibility complex class II antigen expression on pneumocytes and leukocytes in rats. Acute rejection occurred in allogeneic transplants from postoperative days 15 through 25. The expression of class II antigens on endothelial cells, pneumocytes, and leukocytes was further enhanced during the course of allograft rejection in the cytomegalovirus-infected rats compared with the noninfected controls. In cytomegalovirus-positive rats, the rejection grade was higher than that in cytomegalovirus-negative rats on postoperative days 15 through 18. CONCLUSIONS: Our results indicate that cytomegalovirus induces and enhances the expression of major histocompatibility complex class II antigens on endothelial cells, pneumocytes and leukocytes. Upregulation by cytomegalovirus infection may trigger or promote acute rejection by alloantigenic T-lymphocyte stimulation after lung transplantation. By this mechanism it may strongly influence the long-term course of lung transplant rejection.

Acute Disease↗

PubMed1995

Alteration of pulmonary macrophage function by respiratory syncytial virus infection in vitro.

Alveolar macrophages (AL) are the first line of defense against inhaled pathogens and are exposed to virus during the course of a respiratory syncytial virus (RSV) infection. Interference of virus with alveolar macrophage functions may contribute to the risk of acquiring secondary bacterial infections during or after respiratory tract infections with RSV or other viral agents. We studied whether murine AL get infected with RSV and whether they support viral replication in vitro. In addition, the effects of RSV on microbicidal and on immunoregulatory functions were examined. Only a subpopulation of AL expressed viral F proteins after exposure of these cells to RSV. Infected AL released only small amounts of infectious virus into the supernatant. The extent of virus replication in AL seemed to be dependent in part on the amount of IFN induced by the virus, as has been demonstrated by infection of lung tissue macrophages and AL in vitro. In general, RSV infection of pulmonary macrophages appeared to be abortive. Nevertheless, release of reactive oxygen intermediates, phagocytosis, and killing of protozoa were reduced in RSV-infected AL in comparison to noninfected AL. In contrast, RSV stimulated secretion of TNF-alpha, IL-1, and IL-6 in an infectious-dose dependent manner. Along with the increased cytokine release, accessory functions of AL were increased after RSV exposure. Thus, exposure of AL to RSV appeared to stimulate their immunoregulatory functions, whereas the microbicidal activity of these cells seemed to be severely diminished.

Animals↗

PubMed1995

Induction of endothelial adhesion molecules by rat cytomegalovirus in allogeneic lung transplantation in the rat.

Cytomegalovirus (CMV) infection is known to be a major risk factor for the development of chronic transplant rejection in heart and lung transplantation. A possible mechanism for the induction of lung transplant rejection by CMV infection is the inflammatory upregulation of adhesion ligand molecules by the viral infection leading to an increased endothelial-leucocyte interaction. To study this question, an experimental model was established in the rat using a rat cytomegalovirus (RCMV) infection and acute lung transplant rejection in left single lung transplantation. The distribution of RCMV, intercellular adhesion molecule-1 (ICAM-1) and its leucocyte receptor CD11a (LFA-1) were investigated by immunohistochemistry. The viral infection was observed in transplant lungs of infected hosts as early as day 11. The expression of ICAM-1 on endothelial cells was induced and enhanced by RCMV infection, and infiltration of CD11a-positive leucocytes found to be increased in infected recipients. An acceleration of the rejection of the allografts by the hosts was found.

Animals↗

PubMed1994

Interaction of alveolar macrophages and respiratory syncytial virus.

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract illness in infants. However, the mechanisms leading to resolution of RSV infections are poorly understood. Since alveolar macrophages play an important role in defending the respiratory tract against infectious agents we investigated the interactions of RSV with these cells. Murine alveolar macrophages were challenged in vitro with RSV at different multiplicities of infection. The percentage of macrophages expressing viral antigen was determined by staining with monoclonal anti-RSV antibodies and evaluation by fluorescence microscopy or FACS analysis. The ability of macrophages to support virus replication was measured by a plaque forming assay on HEp-2 cells. Cell lysates of macrophages contained only small amounts of viable RSV in comparison to disrupted HEp-2 cells. The amount of viable RSV as well as the percentage of macrophages expressing viral antigen decreased rapidly over time. Activated macrophages had a reduced virus load in comparison to resting macrophages. RSV infected macrophages released biologically active tumor necrosis factor (TNF) in a virus dose dependent manner. In contrast, a high virus inoculum resulted in reduced microbicidal activity and oxygen radical production. Our results suggest that RSV infection influences different functions of alveolar macrophages in various ways. Since TNF is thought to restrict viral replication in several cell types it may play a role in limiting virus replication.

Animals↗

PubMed1994

Pulmonary macrophages.

Interest in pulmonary macrophage research has greatly increased as is now possible not only to work with the easily accessible alveolar macrophages but also with macrophages prepared from lung tissue, such as the interstitial macrophages, dendritic cells and intravascular macrophages. A fascinating aspect is that, in one organ, the modulation of macrophage functions according to their anatomical localization can be studied. This article tries to review some of the modern aspects of research on pulmonary macrophages. These include localization and origin of the various subpopulations, membrane receptors and surface markers, arachidonic acid metabolism, antimicrobial activity, cytokine production and some aspects of macrophage involvement in sarcoidosis and idiopathic lung fibrosis.

Animals↗

PubMed1993

Polysaccharides isolated from plant cell cultures of Echinacea purpurea enhance the resistance of immunosuppressed mice against systemic infections with Candida albicans and Listeria monocytogenes.

Polysaccharides (EP) isolated from large scale plant cell cultures of Echinacea purpurea, have been shown to activate human and murine phagocytes. In this study we investigated the influence of EP on the nonspecific immunity in immunodeficient mice. EP was effective in activating peritoneal macrophages isolated from animals after administration of cyclophosphamide (CP) or cyclosporin A (CsA). EP-treated macrophages exhibited increased production of tumor necrosis factor-alpha (TNF) and enhanced cytotoxicity against tumor target WEHI 164 as well as against the intracellular parasite Leishmania enrietti. After a CP-mediated reduction of leukocytes in the peripheral blood, the polysaccharides induced an earlier influx of neutrophil granulocytes as compared to PBS-treated controls. EP treatment of mice, immunosuppressed with CP or CsA, restored their resistance against lethal infections with the predominantly macrophage-dependent pathogen Listeria monocytogenes and predominantly granulocyte-dependent Candida albicans. Further, the effects of EP in allogeneic bone marrow chimeric mice are discussed. These findings may have therapeutical implications in prophylactic treatment of opportunistic infections.

Animals↗

PubMed1991

Application of purified polysaccharides from cell cultures of the plant Echinacea purpurea to mice mediates protection against systemic infections with Listeria monocytogenes and Candida albicans.

Purified polysaccharides from cell cultures of the plant Echinacea purpurea were investigated for their ability to enhance phagocytes' activities regarding nonspecific immunity in vitro and in vivo. Macrophages (M phi) from different organ origin could be activated to produce IL-1, TNF alpha and IL-6, to produce elevated amounts of reactive oxygen intermediates and to inhibit growth of Candida albicans in vitro. Furthermore, in vivo the substances could induce increased proliferation of phagocytes in spleen and bone marrow and migration of granulocytes to the peripheral blood. These effects indeed resulted in excellent protection of mice against the consequences of lethal infections with one predominantly M phi dependent and one predominantly granulocyte dependent pathogen, Listeria monocytogenes and C. albicans, respectively. Specific immune responses to sheep red blood cells (antibody production) and to listeria (DTH) were not affected by the polysaccharides. The possibility of clinical use is discussed.

Animals↗

PubMed1991

Application of purified polysaccharides from cell cultures of the plant Echinacea purpurea to test subjects mediates activation of the phagocyte system.

Polysaccharides purified from large-scale cell cultures of the plant Echinacea purpurea were tested for their ability to activate human phagocytes in vitro and in vivo. These substances enhanced the spontaneous motility of PMN under soft agar and increased the ability of these cells to kill staphylococci. Monocytes were activated to secrete TNF-alpha, IL-6 and IL-1 whereas class II expression was unaffected. Intravenous application of the polysaccharides to test subjects immediately induced a fall in the number of PMN in the peripheral blood, indicating activation of adherence to endothelial cells. This fall was followed by a leukocytosis due to an increase in the number of PMN and a lesser increase of monocytes. The appearance of stab cells and some juvenile forms and even myelocytes indicated the migration of cells from the bone marrow into the peripheral blood. The acute phase C-reactive protein (CRP) was induced, probably due to activation of monocytes and macrophages to produce IL-6. In addition a moderate acceleration of the erythrocyte sedimentation rate was observed. Altogether, as in mice, the polysaccharides could induce acute phase reactions and activation of phagocytes in humans. The possibility of clinical use is discussed.

Adjuvants, Immunologic↗

PubMed1989

Macrophage activation by the polysaccharide arabinogalactan isolated from plant cell cultures of Echinacea purpurea.

In this study, acidic arabinogalactan, a highly purified polysaccharide from plant cell cultures of Echinacea purpurea, with a molecular weight of 75,000, was effective in activating macrophages to cytotoxicity against tumor cells and micro-organisms (Leishmania enriettii). Furthermore, this polysaccharide induced macrophages to produce tumor necrosis factor (TNF-alpha), interleukin-1 (IL-1), and interferon-beta 2. Arabinogalactan did not activate B cells and did not induce T cells to produce interleukin-2, interferon-beta 2, or interferon-gamma, but it did induce a slight increase in T-cell proliferation. When injected ip, this agent stimulated macrophages, a finding that may have therapeutic implications in the defense against tumors and infectious diseases.

Animals↗