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F Kierszenbaum

Publications and source records attributed to F Kierszenbaum.

At least 55 records · Page 3Linked to original sources
PubMed1990

Modulation of sensitivity of blood forms of Trypanosoma cruzi to antibody-mediated, complement-dependent lysis.

The numerous reports on lysis of blood (trypomastigote) forms of Trypanosoma cruzi by specific antibodies plus complement have systematically shown that a certain proportion of parasites survives. However, it is not known whether the insensitive organisms represent a subpopulation (or clones) or a certain developmental phase of otherwise morphologically identical parasites. In this work, we established that partial lysis was not due to the use of insufficient amounts of lytic reagents. Thus, supernatants of lytic reaction mixtures killed the same proportion of T. cruzi as previously unused reagents. Moreover, in parallel tests in which the trypomastigote concentration was up to four times greater than that used in standard lysis tests, the percentages of lysis were comparable. Incubation periods as long as 4 h did not increase the extent of lysis beyond the value observed after only 1 h, indicating that the routinely used 1-h incubation was appropriate. The extent of lysis was not increased by additional amounts of antibody, complement, or both. Instead, trypomastigotes surviving immune lysis, washed, and incubated with fresh diluent for 45 to 120 min before being used in new lysis tests did manifest additional sensitivity to immune lysis. Three successive infections in mice with parasites which had survived immune lysis led to the production of trypanosomes that displayed the same level of resistance to immune lysis as the original, untreated parasite population. Of interest, the average parasitemias of these groups of mice did not evidence a tendency to increase, as might have occurred if an immune-lysis-resistant subpopulation had been selected. Since trypomastigotes exhibiting resistance to immune lysis can eventually become sensitive, resistance to immune lysis does not represent an insensitive parasite subpopulation. This resistance appears to be modulated by the presence of the lytic reagents and might involve expression of as yet unidentified surface components playing a role in complement activation.

Animals↗
PubMed1990

Trypanosoma cruzi-induced suppression of human peripheral blood lymphocytes activated via the alternative (CD2) pathway.

Coculture of blood forms of Trypanosoma cruzi with human peripheral blood mononuclear cells stimulated with anti-CD2(2) and anti-CD2(3) monoclonal antibodies, i.e., via an antigen-independent pathway of T-lymphocyte activation, resulted in marked immunosuppression compared with that in parallel cultures in which parasites were absent. This effect was evidenced by a decreased lymphoproliferative capacity, a significant reduction in the proportion of cells expressing interleukin-2 receptors, and a significant diminution in the cell surface density of this receptor.

Animals↗
PubMed1989

Trypanosoma cruzi reduces the number of high-affinity IL-2 receptors on activated human lymphocytes by suppressing the expression of the p55 and p70 receptor components.

We previously established that Trypanosoma cruzi, the causative agent of Chagas' disease, has the ability to suppress expression of the p55 component of the IL-2R by activated human PBMC. We explored in this work whether the parasite alters the expression of high affinity IL-2R, responsible for the internalization of IL-2 and signal transduction. Radiobinding measurements revealed that the trypanosome indeed inhibited the expression of high affinity IL-2R. Thus, a considerably smaller number of 125I-IL-2 molecules was necessary to saturate the IL-2R on PHA-stimulated PBMC cocultured with T. cruzi than those of control PBMC that had not been exposed to the organisms. Scatchard analysis of equilibrium binding data showed that, in the presence of T. cruzi, the number of high affinity IL-2R per cell was reduced by approximately 80%. The Kd for IL-2 binding to the fewer IL-2R expressed on PBMC exposed to T. cruzi was not significantly different from that of IL-2R on nonsuppressed PBMC. Independent measurements made after cross-linking 125I-IL-2 to its specific receptors with disuccinimidylsuberate showed that both the p55 and p70 components of the IL-2R were markedly suppressed and to comparable extents. These results demonstrate for the first time that T. cruzi suppresses the expression of high affinity IL-2R by human cells, including the p70 chain of the heterodimeric IL-2R. It is noteworthy that the in vitro model system we used in this work to study the mechanisms whereby T. cruzi may induce the immunosuppression that accompanies acute Chagas' disease also lends itself to the exploration of the regulatory mechanisms governing the expression of IL-2R by human PBMC.

Animals↗
PubMed1989

Inhibition by Trypanosoma cruzi of interferon-gamma production by mitogen-stimulated mouse spleen cells.

Infection by Trypanosoma cruzi is accompanied by severe immunosuppression during the acute period. As part of our studies, to define the alterations caused by Trypanosoma cruzi in lymphocyte function, we examined in this work the interferon-gamma (IFN-gamma)-producing capacity of mitogen-stimulated mouse spleen and human peripheral blood mononuclear cells in the presence or absence of blood forms of the parasite. Co-culture of phytohaemagglutinin- or concanavalin A-stimulated spleen cells from normal mice with T. cruzi significantly decreased the levels of IFN-gamma activity found in the supernatants at 48 or 72 h. In contrast, human peripheral blood mononuclear cells, though suppressed by T. cruzi in their capacity to proliferate upon mitogenic stimulation, showed no significant decrease in IFN-gamma production. The addition of exogenous IFN-gamma did not reverse the suppressive effect of T. cruzi on either mouse or human cells. These results revealed, for the first time, the ability of T. cruzi to impair IFN-gamma production by activated mouse lymphocytes. The lack of restoration by exogenous IFN-gamma suggested that the reduced levels of this lymphokine were not, at least by themselves, the causative factor of reduced lymphoproliferation.

Animals↗
PubMed1989

Decreased human IL-2 receptor expression due to a protozoan pathogen.

A number of parasites suppress immune responses during - and in some cases after - their establishment in their hosts. Many instances of altered levels of immunocompetence have been documented, but the early events and mechanisms leading to such impairment have not been elucidated. Here, Felipe Kierszenbaum and colleagues discuss the ability of the pathogenic protozoan Trypanosoma cruzi to suppress the expression of interleukin 2 receptors by human lymphocytes. Absence or reduced levels of this receptor would prevent lymphocytes from receiving the very important growth factor signal that allows them to continue their division cycle and to proliferate after activation.

Animals↗
PubMed1989

Selective suppressive effects of Trypanosoma cruzi on activated human lymphocytes.

The acute phase of Chagas' disease is accompanied by immunosuppression. To explore the underlying mechanism(s), we used an in vitro culture system in which the capacities of activated human peripheral blood mononuclear cells to express interleukin-2 receptors (IL-2R) and proliferate are markedly inhibited in the presence of Trypanosoma cruzi, the etiologic agent. The present work was designed to define the earliest time at which T. cruzi-induced suppression is manifested in terms of IL-2R expression on the cell surface and establish whether expression of other lymphocyte activation markers is also suppressed by the parasite. We found that expression of IL-2R by human peripheral blood mononuclear cells cocultured with T. cruzi and stimulated with either phytohemagglutinin or anti-CD3 (a monoclonal antibody specific for an epitope of the T cell receptor complex T3-Ti) was significantly suppressed as early as 12 h after culture initiation. Both the percentage of IL-2R+ cells and the surface density of IL-2R, measured by flow cytometry, were affected. However, expression of EA1, a human lymphocyte activation antigen known to be expressed 4 to 6 h after stimulation, was not altered by T. cruzi whether phytohemagglutinin or anti-CD3 was used. On the other hand, expression of transferrin receptors (TfR), which first occurs between 20 and 24 h after lymphocyte activation, was markedly suppressed by T. cruzi. This effect was denoted by significant reductions in both the percentage of TfR+ cells and the cell surface density of TfR whether phytohemagglutinin or anti-CD3 was used as the mitogen and was observed at all test times, i.e., at 24, 48, 72, and 96 h. Because expression of IL-2R and TfR is required for lymphoproliferation but that of the EA1 lymphocyte activation marker is apparently not, these results are consistent with the possibility that T. cruzi, at a relatively early stage during lymphocyte activation, selectively affects certain key events on which clonal expansion is dependent. Inhibition of IL-2R and TfR expression by the parasite might play a role in causing the suppressive effects associated with acute Chagas' disease.

Animals↗
PubMed1989

Interaction of human eosinophils or neutrophils with Trypanosoma cruzi in vitro causes bystander cardiac cell damage.

We studied in vitro whether human eosinophils (EOS) or neutrophils (PMN), which infiltrate the cardiac lesions of patients with Chagas' disease, have the potential to contribute to pathogenesis upon interaction with Trypanosoma cruzi. Incubation of EOS or PMN with T. cruzi amastigotes in the medium overlaying heart myoblast monolayers for 1-6 hr resulted in myoblast injury denoted by cell detachment (35-85%) accompanied by a small but reproducible degree of cell lysis (less than 15%). Myoblast injury was not due to infection because the amastigotes did not invade these cells. No significant myoblast detachment or lysis occurred when EOS, PMN or parasites were tested separately. Myoblast injury was evidenced by using a radiometric method and was readily confirmed microscopically. Deposits of peroxidase, major basic protein, cationic protein and neurotoxin from EOS granules were found on myoblasts incubated with EOS plus T. cruzi; PMN myeloperoxidase was detected when PMN and parasites were used, implicating granule components from these inflammatory cells in the mechanisms of myoblast injury. These deposits were absent when the myoblasts were incubated with EOS or PMN alone. Sodium azide (EOS peroxidase inhibitor) and the polyanions heparin and dextran sulphate (which neutralize the toxicity of EOS granule cationic proteins) inhibited myoblast injury caused by EOS-T. cruzi co-cultures. Albumin, gelatin (inhibitors of the EOS peroxidase-H2O2-halide system) and catalase (scavenger of H2O2) were also inhibitory. Cell injury caused by PMN-parasite mixtures was inhibited by catalase and by potassium cyanide or sodium azide (myeloperoxidase inhibitors), suggesting that PMN myeloperoxidase mediated cytotoxicity. Myoblast injury appeared to be mediated by EOS and PMN secretion products since supernatants of co-cultures of EOS or PMN with T. cruzi produced detachment, inhibitable by the reagents listed above. These results, and our previous demonstration of deposits of EOS granule components at necrotic chagasic myocardial lesions, point to EOS and PMN as possible contributors to the pathogenesis of Chagas' disease.

Animals↗
PubMed1989

Effects of IL-4 on macrophage functions: increased uptake and killing of a protozoan parasite (Trypanosoma cruzi).

We studied whether interleukin-4 (IL-4) could modulate two macrophage functions relevant to their microbicidal activity (uptake and killing), using non-invasive [amastigote (AMA)] forms of the protozoan parasite Trypanosoma cruzi. Treatment of cultures of mouse resident peritoneal macrophages (MPM) with the supernatant of cultures of cells transfected with IL-4 cDNA increased both the capacity of the MPM to take up the organisms and the rate of intracellular killing with respect to MPM mock-treated with medium alone. The presence in the medium of a monoclonal antibody specific for IL-4 during MPM treatment inhibited both effects, pointing to recombinant IL-4 (rIL-4) as the active principle in the supernatant. Kinetic studies revealed that at least a 24-hr pretreatment of the MPM with the rIL-4-containing supernatant was required for these effects to be produced. The rate of intracellular parasite killing was also significantly increased when the rIL-4 treatment was applied after AMA ingestion by MPM. This result confirmed that MPM could be activated by rIL-4 for greater intracellular killing and showed that this enhancement was not necessarily dependent on the initial rIL-4-mediated increase in parasite load. The use of scavengers of reactive oxygen reduction intermediates indicated that hydrogen peroxide, superoxide anion and singlet oxygen, but apparently not hydroxyl radicals, were involved in parasite killing modulated by rIL-4. These results document for the first time the capacity of IL-4 to enhance the microbicidal activity of macrophages and suggest that this lymphokine might play a role in host defence against T. cruzi infection.

Animals↗
PubMed1989

Zinc requirement for macrophage function: effect of zinc deficiency on uptake and killing of a protozoan parasite.

The effects of suboptimal levels of zinc, an essential trace element, on the ability of murine macrophages to associate with and destroy a pathogenic parasite, Trypanosoma cruzi, were evaluated. Young adult A/J mice were fed zinc-deficient, zinc-adequate or restricted amounts of a zinc-adequate diet for 28 days. On the basis of weight loss and parakeratosis, the zinc-deficient mice were further divided into moderately and severely zinc-deficient on Day 28. Both the percentage of mouse peritoneal macrophages (MPM) with associated parasites and the number of parasites per 100 macrophages were significantly lower for macrophages from moderately and severely deficient mice compared to MPM from mice fed restricted or zinc-adequate diet. Furthermore, MPM from both zinc-deficient groups of mice killed fewer internalized parasites than did MPM from restricted or zinc-adequate mice. Pretreatment of MPM from zinc-deficient mice with 5 micrograms zinc/ml for 30 min completely restored both their capacity to take up and kill the parasites. Other trace metals tested, including copper, manganese and nickel, failed to reverse the effects of zinc deficiency. These results point to an important role for zinc in the biochemical events associated with macrophage uptake and killing of the parasite.

Animals↗
PubMed1989

Eosinophil activation in acute and chronic chagasic myocardial lesions and deposition of toxic eosinophil granule proteins on heart myofibers.

Cardiac lesions in patients with Chagas' disease are infiltrated with various types of inflammatory cells, including eosinophils (EOS). We determined the proportions of resting and activated EOS in 2 types of chagasic myocardial lesions to establish whether their presence correlated with lesion severity. One lesion type was defined by interstitial infiltration associated with degeneration and necrosis of myocardial fibers; the other type presented mild myocarditis but myofibers were preserved. In all cases (1 patient with acute and 5 patients with chronic Chagas' disease), a marked degree of EOS infiltration was seen in the necrotic areas after staining either with Giemsa or immunohistochemically, using antibodies specific for the EOS cationic protein or the major basic protein of the granule. In contrast, a very small number of EOS was present in areas of the very same tissue sections displaying mild myocarditis and preserved myofibers. Of the EOS present in the necrotic areas, 42-78% were in the activated secretory stage as evidenced immunohistochemically after incubation with a monoclonal antibody specific for an epitope of the secretory but not the storage form of the EOS cationic protein. In areas with mild myocarditis this proportion was much smaller, ranging from 9 to 28%. In all cases, both the total level of resting and activated EOS in the necrotic areas correlated well with the overall degree of severity of myocarditis evaluated histopathologically. Deposits of the major basic cationic proteins of the EOS granules were found on myofibers in the necrotic areas from the acute and chronic cases, indicating EOS degranulation.

Acute Disease↗
PubMed1988

Novel mechanism for Trypanosoma cruzi-induced suppression of human lymphocytes. Inhibition of IL-2 receptor expression.

Co-culture of blood forms of Trypanosoma cruzi, the causative agent of Chagas' disease, with human PBMC impaired the capacity of T lymphocytes to express surface receptors for IL-2. This effect was evidenced by marked reductions in both the proportion of Tac+ cells and the density of Tac Ag on the surface of the positive cells, determined by flow cytometry. The extent of the inhibition increased with parasite concentration. Under optimal or suboptimal conditions of stimulation with either PHA or monoclonal anti-CD3, specific for an epitope of the T3-Ti human T cell Ag receptor complex, the presence of T. cruzi curtailed the capacity of T lymphocytes to proliferate and express Il-2R but did not affect IL-2 production. Furthermore, the addition of exogenous IL-2 did not restore the responsiveness of suppressed human lymphocytes but did when mouse lymphocytes were used instead. Therefore, unlike mouse lymphocytes, human lymphocyte suppression by T. cruzi did not involve deficient IL-2 production and was accompanied by impaired IL-2 utilization. Co-culture of human monocytes/macrophages with suppressive concentrations of T. cruzi increased IL-1 production, and the parasite did not decrease IL-1 secretion stimulated by a bacterial LPS. Therefore, the suppression of IL-2R expression and lymphoproliferation is not likely to have been an indirect consequence of insufficient IL-1 production due to infection of monocytes or macrophages. We have shown that suppression of human lymphocyte proliferation by T. cruzi is not caused by nutrient consumption, absorption of IL-2, lymphocyte killing, or mitogen removal by the parasite. Therefore, these results uncover a novel suppressive mechanism induced by T. cruzi, involving inhibited expression of IL-2R after lymphocyte activation and rendering T cells unable to receive the IL-2 signal required for continuation of their cell cycle and mounting effective immune responses.

Animals↗
PubMed1988

Recombinant tumor necrosis factor enhances macrophage destruction of Trypanosoma cruzi in the presence of bacterial endotoxin.

We examined in this work whether rTNF inhibits the capacity of Trypanosoma cruzi to multiply within murine macrophages or enhances the ability of the phagocytic host cells to destroy internalized parasites. We found that rTNF would not alter the fate of the trypanosomes within macrophages over a 48-h incubation period unless the latter cells were also treated with 1 ng/ml bacterial endotoxin (LPS). Treatment of macrophages with rTNF plus LPS, but not separate treatment with either rTNF or LPS, resulted in a significant decrease in the number of organisms per 100 macrophages with respect to values obtained with mock-treated macrophages. In addition, there was a significant reduction in the proportion of infected macrophages over the 48-h incubation period, indicating parasite clearance by the host cells. The combined effects of rTNF and LPS were seen when macrophages from CBA/J were used but not with LPS-insensitive macrophages from C3H/HeJ mice. Increased trypanosome killing by CBA/J macrophages treated with rTNF plus LPS was not seen when catalase was present in the culture medium, indicating a role for hydrogen peroxide in the cytotoxic effect. These results show that rTNF can affect the fate of T. cruzi within macrophages if LPS is present and point to destruction of internalized organisms rather than inhibition of parasite multiplication as the most likely explanation.

Adjuvants, Immunologic↗
PubMed1988

Trypanosoma cruzi: a specific surface marker for the amastigote form.

Among the known life cycle stages of Trypanosoma cruzi only the amastigote form bound lactoferrin (LF), a glycoprotein produced by neutrophils. This capacity was readily demonstrable by indirect immunofluorescence in amastigotes derived from mice, a mammalian cell culture, or grown in an axenic medium. No LF binding was detectable on trypomastigotes from blood or mammalian cells, insect-derived metacyclics or epimastigotes, or on epimastigotes grown in Warren's medium. Serum levels of LF were increased in mice acutely infected with T. cruzi, and amastigotes from the spleens of these animals were found to have the glycoprotein on their surface. The amastigote LF receptor may have biological significance in parasite-host interaction since mononuclear phagocytes also express a LF receptor, and treatment of these cells with LF has been shown to increase their capacities to take up and kill T. cruzi amastigotes in vitro. The LF receptor is the first marker for T. cruzi amastigotes for which a naturally occurring ligand has been described.

Animals↗
PubMed1988

Toxic effects produced or mediated by human eosinophil granule components on Trypanosoma cruzi.

The eosinophil granule major basic protein, the eosinophil cationic protein, and the eosinophil-derived neurotoxin were found to be lytic for Trypanosoma cruzi trypomastigotes from blood, cell cultures, or insect vectors and for cultured amastigotes. The toxic effects of the major basic and cationic proteins were inhibited by the polyanions heparin and dextran sulfate, in keeping with the cationic nature of these proteins, or by heat denaturation, suggesting that molecular conformation was also relevant. The lytic activity of the neurotoxin was not inhibited by heating at 56 degrees C for 4 hr, establishing an additional difference with the eosinophil cationic protein. Heparin had only a slight inhibitory effect on the toxicity of the neurotoxin, and dextran sulfate was inactive even at 25 mg/ml. Although both the eosinophil cationic protein and the neurotoxin possess ribonuclease activity, only the toxicity of the latter was abolished by the ribonuclease inhibitor RNasin (Promega, Madison, Wisconsin) or by a competitive substrate, yeast ribonucleic acid. Eosinophil peroxidase significantly increased the extent of trypomastigote or amastigote killing by hydrogen peroxide in the presence of iodide. This effect was abrogated by sodium azide, bovine serum albumin, or gelatin, known inhibitors of the eosinophil peroxidase + halide + hydrogen peroxide system. These results suggest that the destruction of T. cruzi trypomastigotes and amastigotes by eosinophils may result from toxic mechanisms involving several granule proteins.

Animals↗
PubMed1988

Effects of alpha- and beta-adrenergic agonists on Trypanosoma cruzi interaction with host cells.

We studied the effects of adrenergic agonists on the capacity of blood trypomastigote forms of Trypanosoma cruzi to associate with (i.e., bind and/or penetrate) host cells in vitro. The extent of T. cruzi association with mouse macrophages in the presence of the beta-adrenergic agonist L-isoproterenol was significantly decreased with respect to mock-treated controls. Similar results were obtained when the parasite was pretreated with L-isoproterenol and was then allowed to interact with untreated macrophages. In contrast, pretreatment of trypomastigotes with either L-phenylephrine or methoxamine-alpha-adrenergic agonists--enhanced their reactivity with macrophages. Interaction with a nonphagocytic host cell was also decreased and increased by parasite pretreatment with beta- and alpha-adrenergic agonists, respectively. The L-isoproterenol and L-phenylephrine effects were no longer detectable 2 and 3 hr after their removal, respectively, and were therefore reversible. Atenolol, a specific beta 1 adrenoreceptor blocker inhibited the L-isoproterenol effect, whereas butoxamine, a specific beta 2 blocker, did not. Thus, beta 1-like but not beta 2-like binding sites appeared to be expressed on T. cruzi. Both prazosin and yohimbine, preferential alpha 1- and alpha 2-receptor blockers, respectively, abolished the L-phenylephrine effect. The opposite effects of alpha- and beta-adrenergic agonists suggested that the infectivity of T. cruzi may be regulated by activation of surface components comparable to the adreno-receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1988

Immunohistochemical detection of deposits of eosinophil-derived neurotoxin and eosinophil peroxidase in the myocardium of patients with Chagas' disease.

An immunohistochemical study of eosinophil distribution in the inflammatory cell infiltrates of four different types of myocardial lesions associated with Chagas' disease--caused by Trypanosoma cruzi--showed larger numbers of these cells in areas presenting tissue necrosis and degeneration, most notably in patients with the most severe myocarditis from a histopathological stand-point. Using antisera specific for human eosinophil-derived neurotoxin or eosinophil peroxidase, we detected deposits of these secretion products on myofibres and in the interstitium of chagasic myocardium displaying necrosis and degeneration but rarely in other types of lesions. These deposits were not detectable in the myocardium of non-chagasic patients who had died from myocardial infarction (acute or in the scarring stage) or myocarditis secondary to bacterial endocarditis. When human eosinophil-derived neurotoxin was incubated with myoblast monolayers there was a significant cell injury, detachment and lysis. These effects were abrogated by yeast RNA, added as a competitive ribonuclease substrate, and inhibited by the ribonuclease inhibitor RNasin, suggesting that the ribonuclease activity of the eosinophil-derived neurotoxin was involved in the effect. These results suggest a link between eosinophil infiltration and necrosis in chagasic myocardial lesions and point to EDN, and perhaps other toxic eosinophil secretion products, as possible mediators of tissue damage.

Blood Proteins↗
PubMed1988

Kinetics of development of inflammatory lesions in myocardial and skeletal muscle in experimental Trypanosoma cruzi infection.

We studied the kinetics of development of inflammation in the myocardium and skeletal muscles of mice infected with Trypanosoma cruzi by determining the numbers of mononuclear cells (MNC), neutrophils, and eosinophils at tissue sites with varying degrees of damage. In the myocardium, areas with incipient inflammation and preserved tissue had the smallest numbers of inflammatory cells, 96-100% of which were MNC. In lesions where inflammatory cells accumulated in interstitial spaces displacing myofibers, MNC were also predominant (greater than 98%) but were present in larger numbers than in areas with preserved tissue. The number of MNC was even larger in necrotic areas where there was also marked neutrophil infiltration at the time when amastigote nests were frequently present. In skeletal muscle, MNC were also the first cells to infiltrate lesion sites; their numbers increased with the degree of severity of the lesion. Neutrophil accumulation also accompanied skeletal muscle necrosis. A salient difference was eosinophil accumulation in the necrotic lesions of skeletal muscle but not in the myocardium. The results identify MNC as the cell that initiates the inflammatory process in the heart and skeletal muscles of T. cruzi-infected mice. In these tissues the number of MNC appeared to be a good correlate of lesion severity.

Animals↗