Biomedical subjects

F Kierszenbaum

Publications and source records attributed to F Kierszenbaum.

At least 127 records · Page 7Linked to original sources

PubMed1983

Exacerbation of Trypanosoma cruzi infection in mice treated with the immunoregulatory agent cyclosporin A.

Treatment with the immunoregulatory fungus metabolite cyclosporin A exacerbated the course of Trypanosoma cruzi infection in outbred as well as in inbred BALB/c mice. This effect was not observed in congenitally athymic, nu/nu, mice but was readily reproduced in their thymus-bearing, nu/+, littermates. These results suggest that the deleterious action of cyclosporin A on the course of experimental Chagas' disease results from activity of the drug on thymus or thymus-derived lymphocytes and emphasizes the role of T cells in host defense against T. cruzi infection.

Animals↗

PubMed1982

Alteration of the immune and nutritional status of mice by synergy between zinc deficiency and infection with Trypanosoma cruzi.

Since zinc deficiency has been shown to have a profound effect on the immune system of the mouse, it was of interest to evaluate the effects of the deficiency on host resistance to infection. The parasite Trypanosoma cruzi, which infects millions of South Americans each year, was chosen for study. Balb/c mice were fed to either zinc-deficient (1.0 micrograms Zn per gram), restricted (51 micrograms Zn per gram) or zinc-adequate diet (51 micrograms Zn/g). After 8 days on the purified diets, part of the mice from each dietary group were infected with 5 x 10(4) T. cruzi, a dose of this subline of the parasite that was normally sublethal. Twenty-two days postinfection, 80% of the mice in the infected zinc-deficient group were dead. The only other death (10%) occurred in the restricted, infected group. Prior to death the infected zinc-deficient group had a parasitemia that was 50 times greater than that of infected mice from the restricted or zinc-adequate groups. In all infected dietary groups, food intake and/or body weights were reduced in comparison to their uninfected counterparts. The data suggest that zinc deficiency and T. cruzi interact synergistically to profoundly alter both the nutritional and immune status of the host. The experiments also demonstrate the extreme vulnerability of zinc-deficient mice to some pathogens.

Animals↗

PubMed1982

Trypanosoma cruzi: deficient lymphocyte reactivity during experimental acute Chagas' disease in the absence of suppressor T cells.

Infection of mice with Trypanosoma cruzi has been shown to lead to an impaired ability of lymphocytes to proliferate in response to mitogenic stimulation which is manifested during the acute period of the disease. A possible involvement of suppressor T lymphocytes has been postulated by other authors and was investigated in this work as a part of our efforts to disclose the mechanisms underlying the immunologic deficiency. Spleen cells from acutely infected CBA/J mice readily exhibited unresponsiveness to stimulation with concanavalin A, phytohaemagglutinin or a bacterial lipopolysaccharide. However, these cells were unable to reduce the responses that normal syngeneic-mouse spleen cells mounted to these mitogens when cultured together in equal proportions. Furthermore, removal of the Lyt 2.1-bearing cells, known to include the suppressor T cell subpopulation, from infected mouse splenocyte suspensions, did not alter the deficient responsive status of the remaining cells. These results, together with the severe depletion of the T-cell compartment which occurs in the spleens of animals acutely infected with T. cruzi, do not support an important role of suppressor T lymphocytes in the noted deficiency in lymphoid cell reactivity to mitogens. Reduced numbers of responder cells, intrinsic lymphocyte alterations or suppression by cells other than T lymphocytes remain plausible explanations to be explored.

Animals↗

PubMed1982

Biochemical requirements for intracellular invasion by Trypanosoma cruzi: protein synthesis.

The effects of irreversible inhibition of protein synthesis by pactamycin in either infective forms of Trypanosoma cruzi or mammalian host cells on cellular invasion by this human pathogen were investigated. Treatment of bloodstream forms of T. cruzi with pactamycin markedly reduced their ability to bind either fibroblast-like cells of monkey origin or myoblasts of rat origin. The number of amastigote forms that could be established intracellularly was also significantly decreased with respect to control values obtained when mock-treated (medium alone) trypomastigotes were incubated with the cells. Pactamycin treatment also reduced the infectivity of T. cruzi trypomastigotes for mice as evidenced by both significantly reduced parasitemia levels and mortality rates when compared with those of control mice infected with mock-treated parasites. Inhibition of protein synthesis in the host cells neither prevented cell infection by untreated trypomastigotes nor altered the percentages of infected cells or the magnitude of the infection in vitro. These results indicate that protein synthesis is a requirement for cell invasion by T. cruzi and that the parasite can establish itself and replicate within cells relying on its own protein synthesis ability.

Animals↗

PubMed1982

Growth of isolated amastigotes of Trypanosoma cruzi in cell-free medium.

Amastigotes of Trypanosoma cruzi were purified from overlays of infected Vero cell cultures by centrifugation over a discontinuous gradient of metrizamide. Pure amastigote preparations were usually recovered from the pellet under the layer of specific gravity 1.086. The isolated amastigotes grew in cell-free ML-15HA medium. Growth rate for the different strains of T. cruzi were in the order Y greater than Tulahuen greater than CL. The generation time of amastigotes in ML-15HA medium was 16.8, 18.0 and 26.4 h for the Y, Tulahuen, and CL strains, respectively, in the presence of 5% CO2, and 16.8, 31.2, and 36.4 h, respectively, in the absence of CO2. Intracellular amastigotes did not differ ultrastructurally from amastigotes from either the density-gradient fractionation or culture in cell-free medium.

Animals↗

PubMed1982

Immunological properties of peripheral rat lymphocyte subpopulations reacting selectively with guinea pig complement.

Functional properties of peripheral rat T lymphocytes selectively affected by reaction with guinea pig serum (GPS) complement (C) were studied in this work. Cells sensitive to GPS cytotoxicity represented 2-7% of the nucleated cells in the spleen and 1-4% in lymph nodes. Responses of spleen and lymph node cells to Con A and PHA were markedly reduced following treatment with GPS whereas LPS-induced responses were not altered. GPS treatment also abrogated both the specific response of lymph node cells to a protein antigen and the production of leukocyte migration inhibitory factor by splenic cells. By contrast, GPS treatment significantly increased the reactivity of spleen and lymph node cells to alloantigens and enhanced the in vitro immune responsiveness of splenocytes to sheep erythrocytes. These results highlight the selective reactivity of guinea pig C with discrete subsets of immunoregulatory peripheral rat T lymphocytes.

Animals↗

PubMed1982

Characterization of the antiviral activity produced during Trypanosoma cruzi infection and protective effects of exogenous interferon against experimental Chagas' disease.

Mice infected with Trypanosoma cruzi have been shown to develop an antiviral activity in their sera as early as 24 hr postinfection. This activity was characterized in this work as alpha/beta interferon by the following criteria: resistance to pH 2 treatment, sensitivity to incubation at 56 C, or to trypsin treatment, or to actinomycin D treatment, and inactivation by antibody specific for alpha/beta interferon produced in L cells. Mice receiving exogenous alpha/beta interferon in seven daily doses starting on the day of infection with T. cruzi displayed an enhanced resistance evidenced by significantly decreased parasitemias with respect to those of infected animals receiving a mock preparation lacking interferon activity. Direct incubation of T. cruzi with interferon had no consequence on the motility, infectivity or virulence of the parasite. These results suggest a possible role for interferon in inducing enhancement of host resistance against T. cruzi infection.

Animals↗

PubMed1982

Inhibitory action of elevated levels of adenosine-3':5' cyclic monophosphate on phagocytosis: effects on macrophage-Trypanosoma cruzi interaction.

The effects of agents that elevate intracellular levels of cyclic AMP on the in vitro interaction of mouse peritoneal macrophages with virulent bloodstream forms of a reticulotropic strain of Trypanosoma cruzi were investigated as a part of our efforts to define the requirements for tissue invasion by this intracellular human pathogen. At optimal, non-toxic concentrations, both L-isoproterenol and prostaglandin E1, agents that increase cyclic AMP levels by activating adenylate cyclase via different mechanisms, reduced the uptake by T. cruzi by the macrophages by approximately 30 and 70%, respectively, and also caused a reduction in the numbers of macrophages capable of incorporating the parasites. Similar results were obtained when either theophylline, which increases cyclic AMP levels by inhibiting the catabolic effect of phosphodiesterase activity, was incorporated into the cultures or by direct addition of dibutyryl cyclic AMP. Reductions produced with optimal concentrations of these drugs amounted to approximately 40 to 50%. The present results indicate that binding and uptake of virulent forms of a reticulotropic strain of T. cruzi by macrophages from a susceptible host are under the regulatory influence of cellular cyclic AMP levels.

Animals↗

PubMed1982

Inhibition of antibody-dependent eosinophil-mediated cytotoxicity by heparin.

Killing of bloodstream forms of Trypanosoma cruzi, the unicellular parasite that causes Chagas' disease in humans, by human eosinophils in the presence of specific antibody to the parasite was inhibited by the polyanion heparin in a dose-dependent manner. The concentration of heparin required to completely abolish eosinophil-effected killing of the flagellate increased as the eosinophil to parasite ratio increased. These results suggest that antibody-dependent eosinophil-mediated cytotoxicity is mediated by basic constituents of the eosinophil granule.

Antibody Specificity↗

PubMed1982

Immunologic deficiency during experimental Chagas' disease (Trypanosoma cruzi infection): role of adherent, nonspecific esterase-positive splenic cells.

The involvement of adherent splenic cells in the production of deficient lymphocyte responses during the acute phase of experimental Chagas' disease was investigated. When cultured together, purified adherent splenocytes from mice acutely infected with Trypanosoma cruzi caused a significant reduction in the responses of normal mouse spleen cells to T and B cell-specific mitogens. Similar observations were made when infected mouse adherent splenocytes were co-cultured with normal mouse nonadherent cells. Exchange of adherent cells in infected mouse spleen cells suspensions for adherent cells from uninfected mice resulted in increased responses to stimulation with the T and B cell mitogens tested. Treatment of infected mouse cell suspensions with indomethacin improved the responsiveness of these cells to the mitogens. These results support the concept that the immunosuppression that is characteristic of experimental acute Chagas' disease is at least in part mediated by an adherent cell population and is dependent on a prostaglandin-mediated mechanism.

Acute Disease↗

PubMed1982

Inhibition of macrophage-Trypanosoma cruzi interaction by concanavalin A and differential binding of bloodstream and culture forms to the macrophage surface.

The initial interaction between the surfaces of mouse peritoneal macrophages and Trypanosoma cruzi was examined using bloodstream (trypomastigote) and culture (epimastigote) forms of a predominantly reticulotropic strain of the parasite. Pretreatment with Con A resulted in a marked inhibition of macrophage binding of both forms of the parasite. Con A inhibition of epimastigote binding persisted for at least 4 hr after exposure to Con A whereas the trypomastigote-binding ability of macrophages showed a significant spontaneous recovery (57-79%) after 1 hr whether or not the parasites were present in the cell cultures during that time. Binding of Con A to the macrophage was required for inhibition of parasite attachment since incubation of Con A-treated cells with alpha-methyl mannoside prevented the inhibitory phenomenon when either epimastigotes or trypomastigotes were used. This monosaccharide had an inhibitory effect of its own which was not as marked as that produced by Con A and affected epimastigote but not trypomastigote binding to the phagocytic cells, thus representing an additional difference in the modes of interaction of these forms of the parasite with the macrophage surface. Furthermore, inhibition of either trypomastigote or epimastigote binding to macrophages was not caused by succinyl-Con A (which consists of two monomeric Con A subunits whereas Con A has four) unless the succinyl-Con A-treated macrophages were further incubated with anti-Con A antibodies. This observation suggests the importance of either molecular size or crosslinking of Con A subunits with consequent membrane rearrangement in causing the inhibitory phenomenon. The antibody preparation had no effect on macrophage binding of T. cruzi when tested by itself. These results highlight distinct characteristics of the binding of two forms of T. cruzi differing in their infective capacity to the surface of a host cell.

Animals↗

PubMed1981

Experimental Chagas' disease: kinetics of lymphocyte responses and immunological control of the transition from acute to chronic Trypanosoma cruzi infection.

The responses of spleen cells from mice infected with Trypanosoma cruzi to stimulation with T (concanavalin A and phytohemagglutinin) or B (lipopolysaccharide) cell-specific mitogens were monitored during the acute, transition, and chronic states of the disease. A marked reduction in the responses of infected mouse cells with respect to those of uninfected animals was observed during the acute stage, regardless of whether or not the infective dose was lethal. Reduced or absent responses were recorded with suboptimal, optimal, and supraoptimal concentrations of the mitogens. Normal levels of responsiveness to concanavalin A, phytohemagglutinin, and lipopolysaccharide were observed during the chronic stage of the disease. The trend of return to normal responses was initiated around day 40 after infection with 25 parasites. At this time, a marked decline in parasitemia levels, cessation of mortality, and disappearance of visible signs of disease began to be observed defining the transition stage that precedes establishment of chronicity. T cell levels of the spleen were markedly reduced during the acute period and returned during the chronic phase. Instead, absolute levels of B cells were significantly increased during the acute period but also normalize in the chronic phase. Immunosuppression of chronically infected mice with cyclophosphamide led to a temporary return to acute infection-type conditions, even in animals with undetectable levels of parasitemia before treatment. These results suggest that reduced T cell responses during acute experimental Chagas' disease might in part to be due to depletion of the T cell compartment. Decreased B cell responses in the presence of significant numbers of B lymphocytes implies a suppressive phenomenon, B cell alteration, or a combination of both possibilities. Recrudescence of the disease after immunosuppression with cyclophosphamide suggests that immunological mechanisms play an important role, not only in the gain of control over T. cruzi infected by the host but also in the maintenance of the chronic status.

Acute Disease↗

PubMed1981

Proliferative responses of central and peripheral rat lymphocytes elicited by cord factor (trehalose 6,6'-dimycolate).

Cord factor--a mixture of 6,6'-diesters of alpha, alpha-D-trehalose with natural mycolic acids--which is purified from mycobacteria and other microorganisms, is known to have adjuvant activity as well as to enhance nonspecific resistance to infections and tumor development. In this work, trehalose 6,6'-dimycolate (TDM) was found to induce proliferative responses in rat thymus and lymph node cells. With the thymus cells, TDM responses were greater after removal of the adherent cell subpopulation. Consistent with this observation was the finding that addition of phagocytic cells purified from peritoneal or lymph node cell suspensions to nonadherent thymocytes abrogated the response of thymocytes to TDM. With the lymph node cells, the presence or removal of adherent cells had no major consequence on the TDM-induced proliferative response, since similar increases in deoxyribonucleic acid synthesis were observed with unfractionated and nonadherent cells. The difference between the sensitivities of thymus cells and lymph node cells to regulation by adherent cells indicated the existence of more than one type of TDM responder cell in rats. TDM also displayed marked stimulatory activity on thymus and lymph node cells from germ-free rats, ruling out the possibility that TDM might have triggered a specific, secondary, in vitro immune response. Expansion of a selected cell population(s) triggered by TDM may be involved in the manifestation of adjuvant activity and possibly other immunological properties of cord factor.

Animals↗

PubMed1981

Increased serum levels of an interferon-like activity during the acute period of experimental infection with different strains of Trypanosoma cruzi.

A marked development of an interferon-like antiviral activity was observed in the serum of mice infected with Tulahuén strain Trypanosoma cruzi as early as 24 hours after infection with 500 parasites. Such activity remained elevated until 48 hours postinfection and was reduced to undetectable levels--characteristic of normal, uninfected animals--by 72 hours. Infection with 10(4) Tulahuén strain T. cruzi resulted in production of somewhat lesser levels of interferon activity detectable 12 and 24 hours postinfection but not after 48 hours. Infection with 500 parasites of the Y strain was also followed by an increased interferon-like activity but this was not detectable until day 2 postinfection. During the chronic phase of the disease, interferon-like activity levels were indistinguishable from those of uninfected animals. The possibility that interferon activity may have a regulatory effect on the course of the infection is discussed.

Animals↗

PubMed1981

Destruction of bloodstream forms of Trypanosoma cruzi by eosinophil granule major basic protein.

Human eosinophils are known to engage in an antibody-dependent cell-mediated cytotoxicity reaction causing destruction of virulent bloodstream forms of Trypanosoma cruzi. A similar cytotoxic effect was found in this work to be produced by the major basic proteins (MBP) purified from human and guinea pig eosinophil granules. Killing of T. cruzi by these proteins was concentration-dependent, with significant cytotoxicity observed at concentrations as low as 1 x 10(-5) M. Basicity appeared to be an important, but not the only, property required for the MBP molecule to destroy T. cruzi, since highly basic proteins such as arginine-rich histone and cytochrome C were inactive under the same conditions. However, other basic proteins, poly-L-arginine and protamine, lacked cytotoxicity at concentrations which were effective for MBP (1 x 10(-5) M), but killed the flagellates at higher concentrations (5 x 10(-5) M). Furthermore, heparin, an anionic molecule, effectively inhibited the cytotoxic effect of both human and guinea pig MBP on T. cruzi. Heating MBP at 56 degrees C for 4 hours, a treatment which causes the loss of reactivity of MBP with specific antibodies, effectively inhibited the lytic effect on the parasites. In contrast, heating had no effect on the cytotoxic effects of protamine or poly-L-arginine. Specific antiserum to MBP caused a marked reduction in the extent of trypanosome killing by MBP when added to reaction mixtures. The present results suggest that eosinophil-mediated killing of T. cruzi may be due to the discharge of basic granule components by the effector cells which are directly toxic for the parasite.

Animals↗

PubMed1981

Antibody-independent, natural resistance of birds to Trypanosoma cruzi infection.

Complement (C) activity present in normal human serum has been reported to lyse circulating forms of Trypanosoma cruzi following activation by specific host antibodies bound to the surface of the parasites. In view of this observation, we examined the possibility that a similar phenomenon may cause lysis of T. cruzi by avian complement, a mechanism postulated to be responsible for the natural resistance of birds to T. cruzi infection and previously described as being antibody independent. Trypomastigote forms of T. cruzi grown either in lethally irradiated mice or in cell cultures were lysed readily by the sera of agammaglobulinemic chickens. Lytic activity and titers of normal and agammaglobulinemic sera were comparable. The lytic reaction was inhibited by heat inactivation of the sera, or by addition of EDTA or cobra venom factor to the assay mixtures. Lysis of T. cruzi was observed when calcium, but no magnesium ions, were chelated with EGTA. Furthermore, a significant loss of lytic activity was observed when sera from C-depleted chickens were tested. Normal and agammaglobulinemic chickens cleared intravenously injected parasites (from either lethally irradiated mice or cell cultures) from their circulation in 7 min or less whereas C-depleted animals required 1,740 min or longer. Routine examination of the parasites from these two sources by immunofluorescence confirmed the absence of immunoglobulins on their surface. These results emphasize the lack of requirement of antibodies for, and the important role of complement in both the natural resistance that birds exhibit against T. cruzi infection and the lytic activity displayed by avain serum on virulent forms of T. cruzi.

Animals↗

PubMed1981

On evasion of Trypanosoma cruzi from the host immune response. Lymphoproliferative responses to trypanosomal antigens during acute and chronic experimental Chagas' disease.

The ability of spleen cells taken from mice infected with Trypanosoma cruzi to proliferate after stimulation with specific trypanosomal antigens was investigated during the acute and chronic phases of the disease. Lymphoproliferation was minimal or undetectable during the acute period whereas the chronic phase was characterized by significant responses over a wide range of antigen concentration. Transfer of infected mouse spleen cells to cultures of splenocytes from chronically infected animals failed to modify the response of the latter to antigenic stimulation as measured by DNA synthesis. Furthermore, the responses of infected mouse spleen cells collected during the acute period and freed of Lyt 2.1-bearing lymphocytes, a subclass known to contain the suppressor T cells, did not differ significantly from those of untreated aliquots of the same cell suspensions. These results, together with the fact that the T-cell compartment of the spleen was severely depleted during the acute but not the chronic stage of the infection, suggest that the impaired immunological responsiveness of acutely infected mice may be due in part to the absence or marked reduction of responder and/or accessory T lymphocytes. An active role for suppressor T cells in the reduced response to trypanosomal antigens by lymphocytes from mice in the early, acute phase of T. cruzi infection is not supported by the present observations.

Acute Disease↗

PubMed1981

The guinea-pig complement-activating lymphocyte surface component (GPCA): a mouse T-cell marker distinct from Thy-1.

Mouse lymphocytes selectively expressing sensitivity to antibody-independent complement-mediated lysis by normal guinea-pig serum have been previously shown to be identical with T cells. This correlation has raised the question addressed in this work of whether or not the complement-activating surface component and Thy-1 were the same marker. S.49 mouse lymphoblastoid cells, sensitive to killing by anti-Thy-1.2 antibodies plus a source of complement activity devoid of non-specific cytotoxicity, were not sensitive to the non-specific, antibody-independent lytic effects of normal guinea-pig serum. Furthermore, rat thymus cell suspensions containing 93%--95% Thy-1-bearing cells were only partially susceptible (20%--35%) to guinea-pig serum cytotoxicity. Young rat thymus cells virtually devoid of guinea-pig serum-sensitive cells (less than 2%) were readily lysed by antirat Thy-1 and complement (greater than 98%). While these results do not exclude the possibility that Thy-1 may constitute an indirect requirement for T cells to manifest sensitivity to GPS cytotoxicity, it is clear that this antigen does not confer such sensitivity by itself. Therefore, GPCA--the guinea-pig complement-activating marker of murine T cells--is not identical with Thy-1 and represents a distinct surface component of T lymphocytes which manifests itself in terms of a non-specific, but selective ability to activate complement.

Animals↗