Propranolol ameliorates the development of portal-systemic shunting in a chronic murine schistosomiasis model of portal hypertension.

We investigated the role of early portal hypotensive pharmacotherapy in preventing the development of portal-systemic shunting in a portal hypertensive model of chronic murine schistosomiasis induced by infecting C3H mice with 60 cercariae of Schistosoma mansoni. Propranolol was administered in drinking water to 20 animals for a period of 6 wk at a dose of 10 mg.kg-1d-1, starting at 5 wk of schistosomal infection. 32 age-matched mice with chronic schistosomal infection served as controls. All animals were studied 11 wk after the infection. Compared with controls the portal pressure (10.8 +/- 0.40 mmHg) was significantly lower (P less than 0.001) in the propranolol-treated animals (7.9 +/- 0.80 mmHg). Portal-systemic shunting was decreased by 79%, from 12.2 +/- 3.34% in controls to 2.5 +/- 0.99% in the propranolol group (P less than 0.05). Portal venous inflow was reduced by 38% in the propranolol treated animals (2.50 +/- 0.73 ml/min; n = 6) compared with controls (4.00 +/- 0.34 ml/min; n = 8; P less than 0.05). The worm burden, the granulomatous reaction, the collagen content of the liver, and the serum bile acid levels were not significantly different between the two groups of animals. These results demonstrate that in chronic liver disease induced by schistosomiasis, the development of portal-systemic shunting can be decreased or prevented by the reduction of flow and pressure in the portal system.

Pleural effusion as a complication of solitary eosinophilic granuloma of the rib.

A 57 year old man presented with a two week history of right sided chest pain. An admission chest x-ray examination revealed a 2 by 1 cm. lytic lesion of the ninth right rib and right sided pleural effusion. The patient underwent a right thoracotomy during which 700 cc. of blood tinged pleural fluid was drained and a 10 cm. segment of the right ninth rib was excised. The rib lesion showed classic features of eosinophilic granuloma of bone. Cytologic examination of the pleural fluid disclosed abundant histiocytes and eosinophils, consistent with eosinophilic granuloma invading the pleural space. This case is unusual because of the age of the patient and the development of a pleural effusion secondary to the rupture of the tumor into the pleural cavity, the latter not previously reported in the literature.

Hepatic schistosomiasis.

Schistosomiasis is a major, worldwide cause of morbidity and mortality. Disease from the organism Schistosoma mansoni results from egg deposition in the liver, intestines, and other organs and is associated with an intense, granulomatous response from the human host. Clinical manifestations range from mild to severe intestinal forms, and hepatosplenic schistosomiasis, which is associated with hepatic fibrosis, portal hypertension, esophageal varices, and splenomegaly. This article presents information about the epidemiology, immunopathogenesis and clinical aspects of the disease, the relationship between hepatic schistosomiasis and viral infections, diagnosis, therapy, and control strategies for schistosomiasis.

Resistance to reinfection in experimental murine schistosomiasis: role of porto-hepatic hemodynamics.

Experiments were conducted to evaluate critically, and independently of the immune system, the possible role of hemodynamic mechanisms in resistance to schistosomal reinfection. The effects of a challenge schistosomal infection were compared in groups of mice which were either previously infected with schistosomiasis, vaccinated with irradiated cercariae, or underwent partial portal vein ligation for the induction of portal hypertension and porto-systemic shunting. Following infection with 60 cercariae, the appearance of portal hypertension preceded by approximately 2 weeks the development of porto-systemic shunting, which reached maximal values 11 weeks postinfection. Such a primary infection conferred on C3H mice an estimated 90% protection to a 2nd infection, measured by the reduction of worm burden. Worm burdens were also reduced in vaccinated and ligated animals as compared to normal controls. The protection amounted to 30% and 56%, respectively, in the C3H strain and 63% and 75-85%, respectively, in the C57Bl/6 strain. Reduction in worm burden in the ligated animals is believed to be due to the extrahepatic porto-systemic vascular shunts. Hemodynamic as well as immunological factors may account for the resistance to reinfection observed in chronic murine schistosomiasis.

The role of T-cell anergy in the immunomodulation of schistosomiasis.

Schistosomes are capable of causing severe tissue damage, which results from the granulomatous inflammation that develops around the parasite eggs. Characteristic of this inflammatory process is its gradual, spontaneous down-regulation (immunomodulation) as the disease progresses. There has been general agreement that the granulomatous inflammation is a consequence of T(H)-cell-mediated delayed-type hypersensitivity to egg antigens. However, the basis of immunomodulation is less clear and has been attributed to various causes. In this review, Miguel Stadecker proposes a novel mechanism of immunomodulation based on the observation that accessory cells from schistosome-infected individuals are capable of inducing a state of unresponsiveness or energy in a subpopulation of antigen-specific CD4(+) T(H)-cell clones identified with delayed-type hypersensitivity reactions.

Comparison of pyrimidine and purine nucleoside secretion and nucleoside kinase expression in resident and elicited peritoneal macrophages.

Thymidine was found in culture supernatants from both normal peritoneal macrophages and macrophages elicited in vivo with LPS under conditions in which there was no detectable TK activity. Abrogation of thymidine secretion was observed only when elicited macrophages were cultured in the presence of macrophage growth factor (MGF), whereas resident macrophages continued secreting under similar conditions. Similarly, TK activity was induced with MGF only in elicited, but not in resident, macrophages; LPS added in vitro failed to render resident macrophages susceptible to stimulation by MGF. Tests for adenosine and deoxyadenosine in macrophage supernatants proved that these nucleosides were not secreted by these cells. Although AK was consistently expressed in both resident and elicited macrophages, no significant dAK levels could be detected in either cell population. In contrast to TK, both purine nucleoside kinases could not be modulated or induced with MGF. The data indicate different reactivity to MGF by resident and elicited macrophages and a difference in pyrimidine vs purine nucleoside secretion as well as nucleoside kinase expression by these cells.

The regulatory role of the antigen-presenting cell in the development of hepatic immunopathology during infection with Schistosoma mansoni.

A recent meeting held in Berlin (2nd Teupitz Colloquium) focused on the striking ability of mononuclear phagocytes to either stimulate or inhibit a variety of immune and immunopathological responses, and ascribed a distinctive phenotype to the antigen-presenting cells (APC) when exercising these opposite functions. Thus, the phenotype and secretory profile of APC associated with 'classical activation' is achieved following stimulation with pro-inflammatory cytokines such as interferon-gamma, and leads to full T cell activation. On the other hand, it has long been known that T cells may also be downregulated after interacting with certain APC. Many of such APC, originally simply thought to lack or have lost their stimulatory potential, are now thought to be in a state of 'alternative activation', which is associated with a different phenotype and secretory profile that can typically be induced with anti-inflammatory reagents, including the cytokines IL-4, IL-10 and IL-13. The purpose of this article is to analyze the immunopathological events that characterize the infection with Schistosoma mansoni in context with these distinct APC activation pathways. Available evidence from human and experimental data suggests that a desirable outcome of the APC during this parasitic disease is to attain 'alternative activation', which serves to promote and sustain a Th-2-polarized immune response associated with a more favorable anti-inflammatory and host-protective environment.

The inhibition of cutaneous basophil hypersensitivity reactions by a heterologous anti-guinea pig T cell serum.

Systemic treatment with a heterologous anti-T cell serum of guinea pigs immunized with EA in IFA markedly suppressed CBH reactivity to specific antigen and T cell mitogens, as judged by gross reactivity, histology, and skin histamine. The antiserum produced a marked drop in circulating lymphocytes, mainly at the expense of T cells, as indicated by the ability of surviving lymphocytes to rosette with rabbit RBC. It was postulated that the suppression of CBH reactivity is due to the depletion of T cells, which would have released a factor chemotactic for basophils. The data therefore provide further evidence that cutaneous reactions rich in basophils are primarily dependent on a population of T cells.

The regulation of thymidine secretion by macrophages.

The secretion of thymidine by mononuclear phagocytes was correlated with the activity of the enzyme thymidine kinase (TK). Macrophages cultured in regular tissue culture medium released thymidine and did not express TK. However, when macrophages were incubated with medium conditioned by L cells, they expressed TK, incorporated 3H thymidine into trichloroacetic acid precipitable material, and ceased to secrete the nucleotide. Furthermore, replicating P388/D1 cells were induced to secrete thymidine by inhibiting TK with d-glucosamine. These results have demonstrated an inverse relationship between thymidine secretion and the expression of TK. They suggest that thymidine secretion by macrophages may be attributed to their lack of TK activity.

Characterization and antigen-presenting function of a murine thyroid-derived epithelial cell line.

We have developed and evaluated the antigen-presenting function of a murine thyroid-derived epithelial cell line M.5 in order to further investigate the possible role of the thyroid follicular epithelium in the inductive phase of autoimmune thyroiditis. M.5 cells did not express class II major histocompatibility complex encoded (Ia) antigens constitutively, but these could be readily induced with interferon-gamma. We found that Ia expressing M.5 cells were ineffective in stimulating T cell proliferation when tested in a 4-day primary mixed leukocyte reaction (MLR). However, significant T cell stimulation was obtained when phorbol myristate acetate (PMA) was added either to the M.5-T cell co-cultures, or for a brief period to the M.5 cells prior to adding the responder T cells. Cytofluorographic analysis of M.5 cells disclosed that PMA did not significantly alter the expression of Ia antigens. Additional experiments indicated that interleukin 1 (IL-1) was unlikely to represent the co-stimulatory factor generated by PMA. This was based on the observations that M.5 cells failed to secrete significant IL-1 either spontaneously, or in the presence of various stimuli, and that murine recombinant IL-1 failed to substitute for PMA in the activation of T cells. The nature of the co-stimulatory signal is as yet unknown. We conclude from these experiments that a pure population of thyroid-derived epithelial cells may be able to function, under the described circumstances, as antigen presenting cells.

Elucidation and role of critical residues of immunodominant peptide associated with T cell-mediated parasitic disease.

Granulomatous inflammation in schistosomiasis is strictly dependent on CD4+ Th lymphocytes sensitized to egg Ags, but its intensity is genetically regulated. C3H and CBA (H-2k) are strains of mice that develop large granulomas; they also strongly respond to the major egg Ag Sm-p40. We now show that the immunodominant epitope recognized by CD4+ Th cells from infected H-2k mice is confined to 13-mer peptide 234-246 (PKSDNQIKAVPAS), which elicits an I-Ak-restricted Th1-type response. Using a panel of alanine-monosubstituted peptides, we identified Asp237 as the main contact residue with I-Ak. On the other hand, three TCR contact residues were essential to stimulate epitope-specific T cell hybridomas: for two hybridomas these were Asn238, Gln239, and Lys241; and for one, Asn238, Lys241, and Pro244. In one instance, alanine substitution for Gln239 generated an antagonist that blocked subsequent stimulation with wild-type peptide. Most importantly, replacement of Asn238, Gln239, or Lys241 caused a profound loss of polyclonal CD4+ T cell reactivity from schistosome-infected mice. This study identifies the critical residues of immunodominant peptide 234-246 involved in the T cell response against the Sm-p40 egg Ag and suggests that suitable altered peptides may be capable of precipitating its down-regulation.

The immune response and immunopathology in infection with Schistosoma mansoni: a key role of major egg antigen Sm-p40.

The immune response and related granulomatous inflammation in infection with Schistosoma mansoni are ultimately dependent on SEA-sensitized CD4+ Th cells and comprise multiple pathways variously involving the activation and recruitment of different cell populations and the production of different inflammatory cytokines, all under the influence of regulatory genetic factors. The spontaneous downregulation of granuloma formation (immunomodulation), in turn, is a well-known phenomenon, but the full extent of its precipitating factors is still uncertain. This review describes a pathway leading to immunomodulation that features at its centre the down-regulatory cytokine IL-10. This mechanism is attractive because it offers a cogent correlation between findings in the laboratory and those displayed by patients affected with the disease. The Sm-p40 antigen, a major component of schistosome eggs, elicits a strong CD4+ Th cell response in H-2k mice that correlates with intense granuloma formation; in contrast, its immunogenicity is relatively minor during infection of other mouse strains that develop smaller granulomas. Of great interest is that the Sm-p40 antigen only elicits a Th-1 type cytokine response, a phenotype that remains constant even as the overall response to SEA shifts to a Th-2 type. The Sm-p40 molecule has a dominant epitope that is the target of CD4+ Th cells from infected H-2k mice; indeed, a minimal peptide that bears the epitope binds to I-Ak. The importance of pursuing a systematic elucidation of the major egg antigens, resides in the exciting possibility of specifically desensitizing the CD4+ Th cells that mediate granuloma formation, which may achieve meaningful prevention or amelioration of clinical disease.

Distribution and kinetics of mononuclear phagocytes in granulomas elicited by eggs of Schistosoma mansoni.

Previous work has shown that cell suspensions from egg granulomas of Schistosoma mansoni-infected mice contain populations of both I-A-positive and -negative granuloma macrophages (GMs). The present study was undertaken to investigate the distribution of I-A-bearing macrophages within the granulomas, as well as the kinetics of I-A antigen expression by these cells in vivo. Cryostat sections of liver tissue from infected animals, stained with monoclonal anti-I-A antibodies, demonstrated the presence of I-A-positive GMs in peripheral areas of the granulomas, whereas I-A-negative cells concentrated in their centers. For investigation of their expression of I-A antigen, dispersed GMs were studied at time intervals after subjecting infected mice to lethal doses of total body irradiation. I-A half-life on GMs in vivo was estimated to be 2 days, based both on visual detection by immunofluorescence and functionally on the ability of GMs to perform as antigen-presenting cells. Autoradiographic studies, performed on infected liver tissue obtained 1 hour after in vivo administration of tritiated thymidine, showed that macrophages predominantly replicated in peripheral areas of the schistosomal egg granulomas. After longer intervals, however, labeled cells were seen in more central areas of the granuloma, suggesting an overall cell flux from the periphery to the center. These findings indicate that macrophages express I-A antigens in peripheral areas of the granulomas, where macrophage replication and recruitment from the bone marrow take place. They suggest that I-A expression occurs during a limited period of time in "young" macrophages, which later may convert to an I-A-negative phenotype.

Characterization of mononuclear phagocytes in schistosomal egg granulomas of athymic mice.

Macrophages from schistosomal egg granulomas of athymic mice (nu/nu GM) and their euthymic littermates (nu/+ GM) were analyzed phenotypically for the expression of antigens encoded by the I-A subregion of the major histocompatibility complex and for their ability to perform as antigen-presenting cells. Only 11 to 15% of nu/nu GM expressed I-A antigens as compared to 61.5 to 75% of nu/+ GM. Although both populations of cells appeared to be equally effective as antigen-presenting cells appropriately sensitized lymphocytes in the presence of specific antigens--soluble schistosomal egg antigen (SEA) and human gamma-globulin (HGG)--only nu/nu GM, but not nu/+ GM, were found to stimulate I-A-restricted proliferation of schistosome-sensitized T cell populations in the absence of SEA added in vitro. Furthermore, nu/nu GM but not nu/+ GM were shown to exhibit significant proliferative capacity in vitro, but this phenomenon could not account for the observed difference in SEA-independent T cell stimulation. Finally, culture supernatants from nu/nu GM displayed significant thymocyte-stimulating activity, consistent with interleukin 1, which was not observed in nu/+ GM. These findings point to significant differences between nu/nu GM and nu/+ GM, which may be part of an adaptive mechanism of granulomatous reactivity in the absence of a competent T cell system.

Induction of T helper cell unresponsiveness to antigen by macrophages from schistosomal egg granulomas. A basis for immunomodulation in schistosomiasis?

The present studies were undertaken in an effort to understand the role of mononuclear phagocytes in the regulation of the T cell-mediated granulomatous inflammatory response in experimental murine schistosomiasis mansoni. We report that macrophages from schistosomal egg granulomas did not efficiently stimulate, but rather induced marked proliferative unresponsiveness to Ag in an IL-2-producing, I-Ek-restricted, CD4+ Th cell clone specific for pigeon cytochrome c. The unresponsive state of the T cells was achieved after incubation with granuloma macrophages in the presence of the specific Ag fragment 81-104, but not with either of them independently, and was, similarly, restricted by the I-Ek molecule. Equivalent amounts of peritoneal macrophages from schistosome-infected, but not from normal mice, were also effective in inducing T cell unresponsiveness. We postulate that granuloma macrophages, and potentially other accessory cells in schistosome-infected individuals, are similarly capable of inducing anergy in egg Ag-specific Th cells, and that the resulting inhibited T cell reactivity, which translates into failure of lymphokine secretion and of clonal expansion, represents a major basis of the immunologic down-regulation (immunomodulation) of granulomatous hypersensitivity, characteristically seen in this disease.

Schistosoma mansoni: the basis for the antischistosomal effect of cyclosporine A.

A potent antiparasitic effect against a broad range of microorganisms is now known to follow the administration of cyclosporine A (CSA) to a variety of mammalian species and birds. Even though in the case of Schistosoma mansoni a direct antischistosomal effect by CSA has been in principle ruled out, this possible mechanism of action has not been previously explored in depth. In this paper we show that (a) concentrations of CSA of as low as 1 microgram/ml are schistosomulicidal in vitro as determined by morphological criteria, (b) mice receiving antischistosomal regimens in vivo exhibit serum concentrations of CSA that are within the range of toxic doses in vitro, (c) schistosomulicidal concentrations of CSA are maintained in vivo for sufficiently long periods of time to secure parasite death, (d) the antischistosomal activity of heat-inactivated mouse sera closely correlates with their levels of CSA, and (e) independent of the site of administration, CSA offers protection against a schistosomal infection in vivo only when present in the serum. The data strongly support the contention that CSA has a direct effect on the early forms of Schistosoma mansoni, and suggest that interference with a survival mechanism, perhaps common to several parasites, represents one likely mode of action.