Delayed hypersensitivity-type granuloma formation and dermal reaction induced and elicited by a soluble factor isolated from Schistosoma mansoni eggs.

A soluble material has been isolated from schistosome eggs which in minute quantities without the addition of adjuvant induces sensitization to a delayed hypersensitivity type of granuloma forming around intact schistosome eggs. This material is secreted by intact eggs and is found in high concentration in the fluid released during the hatching process. When adsorbed to bentonite particles this substance elicits hypersensitivity type granuloma formation in specifically sensitized animals. The granuloma sensitizing factor also both induces and elicits delayed footpad swelling in mice. Quantities which sensitize with respect to these delayed type reactions do not induce antibody formation detectable by a sensitive hemagglutination. technique within the duration of the above experiments.

Regulation of granulomatous inflammation in murine schistosomiasis. II. T suppressor cell-derived, I-C subregion-encoded soluble suppressor factor mediates regulation of lymphokine production.

In the present study, we extended the analysis of the regulation of inflammatory lymphokine production in mice with schistosomiasis mansoni. Splenic lymphocytes of chronically infected mice were briefly pulsed in vitro by soluble egg antigens, washed, and then cultured overnight. The supernatant culture fluid added to cultures of splenic cells of acutely infected or peritoneal lymphocytes of antigen-sensitized mice inhibited the production of migration inhibition factor (MIF). Elaboration of MIF suppressor factor (MIF-SF) required the Lyt-1-,2+,3+ subset of T lymphocytes. MIF-SF acted only on egg antigen-primed cells and required H-2 compatibility with the target cell for its suppressive effect. Further analysis with recombinant strains revealed that the factor interacted with I-AB or I-C subregion-compatible target cells. Experiments using immunoadsorbent columns with bound anti-I subregion alloantisera indicated that MIF-SF contained I-C subregion-encoded determinants. Extrapolation of this in vitro model to in vivo conditions would indicate that the granulomatous response is modulated by I region-derived suppressor factor(s) that regulate lymphokine production by TDH effector cells.

Regulation of granulomatous inflammation in murine schistosomiasis. In vitro characterization of T lymphocyte subsets involved in the production and suppression of migration inhibition factor.

Host granulomatous inflammation in murine schistosomiasis mansoni is a T cell-mediated immune response, which, at the chronic stage of the disease, undergoes T suppressor lymphocyte-dependent modulation. In the present study this phenomenon was further analyzed in vitro. Spleen cells of mice undergoing modulation (20 wk of infection) when mixed with spleen cells of animals exhibiting vigorous granulomatous responses (8 wk of infection) abrogated in vitro migration inhibition factor (MIF) production by the latter. Characterization of the delayed-type hypersensitivity T lymphocytes involved in lymphokine production showed that they belonged to the Lyt-1+ subset and did not express I region-encoded antigens. In contrast, T lymphocytes involved in the suppression of MIF activity belonged to the Lyt-2+ subpopulation of cells, which expressed I-J- and I-C-subregion determinants. These results suggest that the modulation of the granulomatous hypersensitivity response in mice is the result of T-T cell interaction with subsequent regulation of inflammatory lymphokine production.

Effect of SQ 14225, an inhibitor of angiotensin I-converting enzyme, on the granulomatous response to Schistosoma mansoni eggs in mice.

Murine schistosomiasis is a granulomatous disease associated with high serum and granuloma angiotensin I-converting enzyme (ACE) activity. SQ 14225, a specific competitive inhibitor of ACE, was administered to normal mice and mice infected with Schistosoma mansoni to determine whether this compound could inhibit granuloma ACE activity and modify the size of the granulomatous response to schistosome eggs. Peroral administration of SQ 14225 for 5 wk to infected mice with peak granulomatous responses decreased ACE activity in isolated liver granulomas. Treated mice demonstrated a decrease in granuloma size in the liver, colon, and ileum, and hydroxyproline concentration of isolated liver granulomas was increased. Mean diameters of synchronous pulmonary granulomas, induced by the pulmonary embolization of schistosome eggs into normal and sensitized mice, were decreased by a similar dose of SQ 14225. Withdrawal of SQ 14225 from unsensitized mice with 2-wk-old synchronous pulmonary granulomas induced an increase in inflammation. Infected, but not normal mice receiving SQ 14225 demonstrated reduced portal pressure, liver weight, and body weight. Both normal and infected mice experienced dipsogenesis, expanded intravascular volume, and increased serum ACE. These observations suggest that SQ 14225 can partially inhibit the granulomatous response to schistosome eggs and the pathological manifestations of schistosomiasis. It is possible that ACE has an inflammatory role in granulomatous inflammation.

The role of cytokines in the formation of the schistosome egg granuloma.

Schistosomiasis mansoni is a helminth-induced disease infecting over 120 million people in the tropics. Morbidity and mortality are caused by parasite eggs that evoke in the liver and intestines of infected persons, T cell-mediated granulomatous inflammation and irreversible fibrosis. In the murine model granulomatous inflammation is induced by CD4+ T helper lymphocytes. This short review summarizes recent observations that implicate a variety of lymphokines and cytokines as mediators of the granulomatous inflammatory response. Mediator production was examined in splenocyte as well as granuloma cell cultures of infected or egg granuloma-bearing mice. In the synchronous pulmonary granuloma model generated around i.v. injected eggs in naive mice IL-1 mRNA expression and IL-1 production were detectable within the first 4 days of granuloma growth. After 4-6 days TNF-alpha mRNA message appeared and cytokine production was observed. With the aging of the granuloma, production of both cytokines diminished. Thus, these cytokines are considered to be the primary recruiters of cellular aggregation in granuloma growth. The role of TNF-alpha in granuloma formation was also confirmed in infected mice. Whereas treatment of animals with anti-TNF-alpha antiserum diminished hepatic granuloma size, repeated injection of murine rTNF-alpha into chronically-infected mice enhanced the downmodulated granuloma response. With the administration of specific anti-lymphokine mAbs and recombinant murine lymphokines, as well as serial assays of lymphokine production by splenic, granuloma lymphocytes of infected mice, the role of INF-gamma, IL-2 and IL-4 was delineated. Interferon-gamma was found to be produced very early at the inception of the liver granulomatous response. By the time granulomas reached maximal size (8 wks post infection) production declined. Concurrently IL-2, IL-4 production peaked with maximal granuloma growth and declined with the onset of the immune modulation of the inflammation. Whereas these latter lymphokines appear to play a proinflammatory role, IFN-gamma when administered in large doses diminished granulomatous inflammation, plays a regulatory role in the maintenance of the granulomatous response. The T helper cell population of the granulomas may also influence the lymphokine profile of the developing granuloma. So far precursor type TH0, and TH2 subset of helper cells have been cloned from liver granulomas. The former secreted both IL-2, IL-4 and IFN-gamma lymphokines and adoptively transferred the granulomatous response.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoregulation of granuloma formation in murine schistosomiasis mansoni.

Schistosomiasis mansoni is a chronic, T lymphocyte-mediated granulomatous disease that affects mainly the liver and intestines of the infected host. The chronic inflammatory process and subsequent fibrous repair are the major factors in the pathology of the disease. In the murine model of schistosomiasis at the onset of the chronic stage of the infection, the granulomatous response undergoes spontaneous modulation with concomitant alleviation of the pathologic disturbance. Analysis of the process of modulation revealed that it results from the interaction between inflammatory and regulatory subpopulations of T lymphocytes. At the acute phase of the infection, the granulomatous response is initiated and maintained by inflammatory TDH cells that release lymphokines which mobilize and recruit the macrophages, eosinophils, etc. for the generation of the lesion. Already at this stage, while the inflammatory influence prevails, a low number of suppressor T lymphocytes are present. With the progress of the infection, the overheated inflammatory response is curbed by regulatory processes. At least two, but perhaps more, T suppressor lymphocytes are involved in the maintenance of the modulation of the granulomatous response. Modulation is an active process that needs constant maintenance, probably by recruitment of fresh suppressor cells. Removal of the suppressor population causes an immediate elevation of the granulomatous response. During modulation, T suppressor lymphocytes either abrogate or greatly diminish inflammatory lymphokine production. This in turn may be the cause for decreased cell recruitment and diminution in newly formed granuloma size. Apparently a total abrogation of the granulomatous response is not desirable because released egg antigens can be harmful to liver parenchyma cells. This has been demonstrated both in thymus-deprived and in nude, infected mice. Thus, a smaller inflammatory response has the double advantage of not only being less destructive, but also shielding the underlying tissue from damage by parasite products. The various subpopulations of T lymphocytes communicate with one another by means of soluble suppressor factors that arise from the suppressor T cells. The factors may have different functions. One factor may regulate lymphokine production whereas another may recruit fresh suppressor cells from a pool of precursors. The factors act in an antigen-specific manner. Tentatively, one may assume that these factors are composed of two units: one is the I subregion membrane marker and the other is the specific recognition receptor. The nature of this receptor is still unclear, but it may be an anti-idiotypic determinant.(ABSTRACT TRUNCATED AT 400 WORDS)

Population dynamics of T and B lymphocytes in the lymphoid organs, circulation, and granulomas of mice infected with Schistosoma mansoni.

The T and B lymphocyte composition of the lymphoid organs, peripheral blood, and hepatic granulomas was determined in mice lightly infected with Schistosoma mansoni. Apart from an increase of circulating B cells, no change was seen in the distribution of lymphocytes prior to oviposition. Thereafter (8-20 weeks), a pronounced trend toward increased B and increased T cell percentages occurred throughout the organs. This effect was largely due to marked increases in the B cell population which outweighed increases of T cells occurring at 8 and 16 weeks. By the late chronic period (32 weeks), an overall normalization of percentages was observed due to declining B and/or increasing T cell numbers. Hepatic granulomas also showed notable compositional changes. At the time of maximum granulomatous response (8 weeks), the lymphocyte population of these lesions consisted primarily of T cells. Subsequently, during the time of modulated granuloma formation (12-32 weeks), B-cells became a significant component, comprising 10% of the granuloma cell population. The appearance of B cells within granulomas may indicate that they play a role in modulating granulomatous hypersensitivity.

The effect of splenectomy on the pathophysiology and egg-specific immune response of Schistosoma mansoni-infected mice.

Splenic involvement in murine schistosomiasis mansoni is manifested by splenomegaly, hyperplasia of the lymphoid and mononuclear phagocytic elements, and strong immune responses of splenic lymphocytes to schistosome antigens. In the present study, groups of Schistosoma mansoni-infected mice were splenectomized or sham treated at 1, 4, and 8 weeks of the infection, and at 12 weeks changes in pathophysiology, humoral, and granulomatous responses as well as liver fibrosis were examined. Splenectomy had no influence on the body and liver weight or portal presure of the infected mice. Mice which underwent splenectomy at 8 weeks developed anemia. Whereas splenectomy performed at 8 weeks of the infection did not affect the anti-schistosome egg antigen humoral response of the animals, it caused significant enhancement in the liver granulomatous reaction. Increased granuloma size did not result in a concomitant increase in the extent of liver fibrosis as measured by hydroxyproline content. It is concluded that the spleen may play an important role in the immunoregulation of the egg-specific granulomatous inflammatory response.

Induction of collagen synthesis in cultured human fibroblasts by live Schistosoma mansoni eggs and soluble egg antigens (SEA).

There is a dearth of knowledge on the tissue fibrosis that contributes to the pathology of schistosomiasis mansoni. The present study was designed to test the direct effect of live schistosome eggs and soluble egg antigens (SEA) on cultured normal human fibroblasts. Coincubation for 3 days of fibroblast monolayers with 100-500 live eggs/ml medium or equivalent amounts of SEA caused enhanced incorporation of labelled proline. The newly synthesized polypeptides were sensitive to purified collagenase enzyme activity. Collagen synthesis was also verified by measuring increased hydroxyproline content in fibroblasts. Whereas low numbers of eggs stimulated fibroblast activity, 500 eggs/ml medium caused a disarray in the arrangement of cells, with cytoplasmic granulation, cell detachment and death. These results indicate that fibroblast stimulation and collagen synthesis may also be triggered by the direct action of egg secretions on tissue fibroblasts.

Collagen isotypes, laminin, and fibronectin in granulomas of the liver and intestines of Schistosoma mansoni-infected mice.

Patterns of fibrosis within hepatic and intestinal granulomas of Schistosoma mansoni-infected mice were analyzed by indirect immunofluorescence. Deposition of collagen isotypes, laminin, and fibronectin was evaluated semiquantitatively between 8 and 20 weeks of the infection. Liver granulomas were the largest at 8 weeks and contained low amounts of type I and higher amounts of type III collagen and fibronectin. Collagen deposition became pronounced as infection progressed. The relative amounts of type I collagen deposits rose and equalled that of type III. In the smaller immunomodulated granulomas at 20 weeks both types I and III were high, and type IV collagen deposition was observed. Fibronectin and laminin deposits were also detected. The small ileal granulomas did not change their size during the course of the infection. At 8 weeks, connective tissue matrix deposition was barely detectable within these lesions. Gradually, small deposits of types I and III appeared in equal amounts and attained highest levels by 20 weeks of the infection. Fibronectin deposits at that time were very prominent but laminin and type IV collagen were absent. Colon granulomas at 8 weeks of the infection were only somewhat smaller than those of the liver, yet contained very sparse deposits of types I and III collagen. During the ensuing weeks collagen deposits rose only slightly. By 20 weeks the granulomas diminished in size and within those lesions type III collagen was predominant. Whereas the presence of fibronectin was pronounced, type IV collagen and laminin were detectable only in trace amounts. These observations indicate the existence of important organ-related differences in the intragranulomatous deposition of connective tissue matrix.

Differential expression of collagen, MMP, TIMP and fibrogenic-cytokine genes in the granulomatous colon of Schistosoma mansoni-infected mice.

Schistosomiasis mansoni is a major helminthic disease of the tropics characterised by chronic hepatic and intestinal granulomatous inflammation and fibrosis. The fibrotic response is regulated by the amount of collagen deposited in the tissues and the degradation of that collagen by matrix metalloproteinases (MMP). In the murine model of the disease, although hepatic granuloma formation and the ensuing fibrosis have been thoroughly examined, there is a dearth of information on the intestinal fibrotic process. The expression of fibrosis-related genes in the colons of chronically infected mice has therefore been investigated. Compared with that seen in uninfected mice, the expression of the genes coding for collagen of types I, III and IV was upregulated. Similarly, the messages for MMP-2, MMP-3 and MMP-8 were elevated, indicating the potential for collagen degradation. The genes for two tissue inhibitors of metalloproteinases (TIMP), TIMP-1 and TIMP-4, were, however, expressed at higher levels than those coding for the MMP. As a corollary, expression of the genes coding for three fibrogenic cytokines, transforming growth factor-beta, tumour necrosis factor and interleukin-4, was elevated. These data indicate that an imbalance in MMP:TIMP expression and enhanced levels of the messages for fibrogenic cytokines underlie the mechanism(s) of the colonic fibrosis seen in mice chronically infected with Schistosoma mansoni.

A novel nonsteroidal antifibrotic oligo decoy containing the TGF-beta element found in the COL1A1 gene which regulates murine schistosomiasis liver fibrosis.

Schistosomiasis mansoni disseminated worm eggs in mice and humans induce granulomatous inflammations and cumulative fibrosis causing morbidity and possibly mortality. In this study, intrahepatic and I.V. injections of a double-stranded oligodeoxynucleotide decoy containing the TGF-beta regulatory element found in the distal promoter of the COL1A1 gene into worm-infected mice suppressed TGF-beta1, COL1A1, tissue inhibitor of metalloproteinase-1, and decreased COL3A1 mRNAs to a lesser extent. Sequence comparisons within the mouse genome found homologous sequences within the COL3A1, TGF-beta1, and TIMP-1 5' flanking regions. Cold competition gel mobility shift assays using these homologous sequences with 5' and 3' flanking regions found in the natural COL1A1 gene showed competition. Competitive gel mobility assays in a separate experiment showed no competition using a 5-base mutated or scrambled sequence. Explanted liver granulomas from saline-injected mice incorporated 10.45 +/- 1.7% (3)H-proline into newly synthesized collagen, whereas decoy-treated mice showed no collagen synthesis. Compared with the saline control schistosomiasis mice phosphorothioate double-stranded oligodeoxynucleotide treatment decreased total liver collagen content (i.e. hydroxy-4-proline) by 34%. This novel molecular approach has the potential to be employed as a novel antifibrotic treatment modality.

Immunopathology of Schistosoma mansoni infection.

Schistosomiasis mansoni is a chronic helminthic disease that affects about 100 million people in the tropics. The worms have a life span of 5 to 10 years, and they live in the mesenteric veins of the host. Lightly infected individuals are asymptomatic or manifest mild intestinal symptoms. Heavily infected individuals often develop severe morbidity with hepatosplenomegaly, sometimes with a fatal outcome. Morbidity is attributed to the strong humoral and T-cell-mediated host immune responses developed to a variety of parasite antigens and expressed as tissue inflammations. The immunopathology includes dermatitis, immune complex-mediated kidney disease, and, chiefly, T-cell-mediated granuloma formation and fibrosis around disseminated parasite eggs. This review describes the mechanisms of induction and expression of immunopathology in infected persons and experimental animals. Immunoregulatory mechanisms that modulate the enhanced immune responses and may ameliorate excessive morbidity are discussed.

Characterization of granuloma T lymphocyte function from Schistosoma mansoni-infected mice.

This study was undertaken to characterize and compare T lymphocyte function from the vigorous and modulated liver granulomas of Schistosoma mansoni-infected mice. Although both types of lesion contained equal percentages of T lymphocytes, the T cell subset distribution was different. For vigorous lesions, the ratio of helper/effector to suppressor/cytotoxic T cells was 2 to 3:1. For modulated lesions the ratio was lower (1:1). Differences in the phenotypic profiles of vigorous and modulated granuloma (Gr) T cells were reflected in their functional activity. Vigorous Gr T cells were more active in lymphoproliferation, IL-2 production, and granuloma formation than those from modulated lesions. Moreover, modulated Gr T cells suppressed the functional activity of vigorous Gr T cells in a dose-dependent manner. The selective depletion of T cell subsets showed that phenotypically, the Gr delayed-hypersensitivity T cell is L3T4+, Lyt-1+ whereas the Gr Ts cell is an Lyt-2+ lymphocyte. Both of these T cell subsets are present in vigorous and modulated lesions. During acute infection, delayed-hypersensitivity T cell lymphocyte functions predominate, whereas Ts lymphocyte functions appear to prevail during chronic infection.

The Schistosoma mansoni egg-derived r38 peptide-induced Th1 response affects the synchronous pulmonary but not the asynchronous hepatic granuloma growth.

The p38 peptide derived from Schistosoma mansoni egg-antigens (SEA) is a preferential inducer of the Th1 response. In the present study, we investigated whether induction of a p38-specific Th1 or Th2 response can influence granuloma development in infected or sensitized mice. Mice sensitized with SEA/IL-12 3 weeks after infection but before worm oviposition commenced developed Th1 cytokine responses and had significantly reduced hepatic granuloma size. Similar immunization with p38/IL-12 induced a strong peptide-specific Th1, mixed SEA-specific Th1/Th2 responses without effect on hepatic granuloma development. Presentation of p38 with alum or alum/IL-12 mixture enhanced Th2 cytokine responses and hepatic granuloma sizes. In the synchronized pulmonary model, sensitization of naïve mice with p38/IL-12 induced a strong Th1 cytokine production to p38 and SEA, led to a moderate increase in granuloma growth at days 4 and 8 following egg injection and actually promoted the resolution of the lesion by day 16. Sensitization with p38 in alum induced Th2 cytokine production and generated the largest granulomas whereas the p38/alum/IL-12 sensitized group showed intermediate results in cytokine production and granuloma growth. Thus, in infected mice, the p38 induced strong Th1 response was insufficient to cross-regulate the evolving Th2 environment that generated large granulomas.