Eosinophils and immune mechanisms

Regulation of Fibroblast Functions by Products of Schistosomal Egg Granulomas: Potential Role in the Pathogenesis of Hepatic Fibrosis

Recent observations suggest a molecular link between granuloma formation and hepatic fibrosis in schistosomiasis. Egg granulomas isolated from Schistosoma mansoni-infected mice, when cultured in serum-free medium, produce a variety of biologically active molecules that affect fibroblast function. One group of molecules--proteins with an estimated relative molecular mass (Mr) of 30 000--stimulate fibroblast proliferation in vitro. These molecules have interleukin (IL)-1-like activity when assayed in thymocyte cultures but are biochemically distinct from previously characterized murine IL-1. Fibroblast mitogenic activity is also produced by macrophages isolated from granulomas and by extracts of S. mansoni eggs. The egg-derived activity is distinct from the granuloma cell-derived material on the basis of Mr and isoelectric point determinations. Egg extracts also contain concanavalin A-binding substances which are not directly mitogenic for fibroblasts but can stimulate spleen cells from infected mice to produce fibroblast mitogenic activity in vitro. A large chemoattractant molecule (greater than 200 000 Mr) for fibroblasts has also been identified in supernatants from granuloma cultures and in supernatants from macrophages isolated from granulomas. This activity is abolished by treatment with anti-fibronectin antibody, suggesting that it is fibronectin or a cleavage product thereof. Molecules similar to or identical with the fibroblast mitogenic factors from the granulomas have been identified, and they inhibit the contraction of fibroblast-populated collagen lattices. These activities may be important in the pathogenesis of hepatic fibrosis in schistosomiasis, and pharmacological modification of their production or of their effects on target fibroblasts might theoretically prevent hepatic fibrosis in this disease.

Kinetic study of eosinophil chemotactic factor production with reference to eosinophilia and granuloma formation in mice infected with Schistosoma japonicum

Kinetic changes of eosinophil chemotactic factor (ECF) production from granulomas, splenic T-cells or mast cells were examined with reference to granuloma formation around newly deposited single eggs in Schistosoma japonicum-infected mice. The peri-ovular granulomas began to appear at around 5 weeks post-infection (p.i.). Their size reached a peak at 6 weeks and then decreased gradually. Up to 8 weeks p.i., eosinophils were the predominant cell type in the granulomas. ECF-release from isolated granulomas paralleled the size of granulomas. Circulating ECF-A, which was assumed to be derived from mast cells, was also detected 6 weeks afterwards in parallel with the level of specific IgE antibody level against egg antigens in the serum. The circulating ECF-A peaked at 8 weeks and decreased after 10 weeks. Spleen cells began to produce ECF specific to bone-marrow eosinophils began at 5 weeks p.i., reached a peak at 6 weeks and then decreased rapidly. On the other hand, the production of ECF specific to eosinophils obtained from the peritoneal cavity began at 6 weeks and decreased rapidly thereafter. These results suggest that various kinds of host-derived ECFs seem to contribute, in one way or an other, to the accumulation of eosinophils in and around granulomatous lesions. The possible role of these ECFs in eosinophil mobilization from the site of production to the inflamed site is discussed.

In vitro and in vivo evidence that autoimmune reactivity to collagen develops spontaneously in Schistosoma mansoni-infected mice

Egg-induced granuloma formation in murine schistosomiasis mansoni results from vigorous anti-parasite reaction by activated T cells, macrophages, eosinophils, and fibroblasts. The present study suggests that strain-specific, autoimmune T-cell reactivity directed against host matrix proteins might also contribute to granulomatous hypersensitivity. T cells from infected C57B1/6, but not from CBA or BALB/c mice, proliferative in vitro in response to denatured collagen. T cells from uninfected mice, previously immunized with soluble egg antigen (SEA), did not respond in vitro to collagen. Spleen cells from acutely infected mice, but not chronically infected or uninfected animals, formed granulomas around collagen-coupled polyacrylamide beads in vitro. This response was blocked by anti-collagen antibodies that had no inhibitory effect on in vitro granuloma formation around SEA-coupled beads. In related in vivo studies, granuloma formation was quantitated after iv injection of SEA-, collagen-, or uncoated beads into normal or infected recipients. The mean diameter of lung granulomas induced by collagen-coupled beads in infected mice was significantly greater than the diameter of granulomas around either collagen beads in uninfected mice or uncoated beads in infected mice. these observations indicate that anti-collagen responses develop spontaneously in Schistosoma-infected mice and suggest that such reactivity might play a secondary role in granuloma formation and the pathogenesis of hepatic fibrosis.

Schistosoma japonicum: identification and characterization of neutrophil chemotactic factors from egg antigen

Two neutrophil chemotactic factors were identified in soluble egg antigen preparations of Schistosoma japonicum. The higher-molecular-weight neutrophil chemotactic factor was not separable from eosinophil chemotactic factor by means of gel filtration, anion-exchange chromatography, isoelectric focusing, or affinity chromatography; this neutrophil chemotactic factor is apparently identical to the higher-molecular-weight eosinophil chemotactic factor which we purified previously from the soluble egg antigen. The chemotactic activity of the eosinophil chemotactic factor for neutrophils was stable to periodate oxidation but was notably affected by heating or Pronase digestion, suggesting that the determinant for neutrophil chemotaxis exists on the peptide moiety of the eosinophil chemotactic factor. The lower-molecular-weight neutrophil chemotactic factor was separable from the higher-molecular-weight eosinophil chemotactic factor by gel filtration or anion-exchange chromatography. This neutrophil chemotactic factor was rather hydrophobic and heat-stable, but was sensitive to Pronase or carboxypeptidase A digestion. These results suggest that the receptors on the surfaces of neutrophils and eosinophils for those chemoattractants would be different from each other. We suppose that neutrophil chemotactic factors and eosinophil chemotactic factors from the eggs are responsible for neutrophil and eosinophil accumulation around the eggs in schistosomiasis japonica.

Granuloma macrophages in murine schistosomiasis mansoni generate components of the angiotensin system

The angiotensin cascade was recently detected in liver granulomas of murine Schistosomiasis mansoni, suggesting an immunoregulatory role for angiotensins in inflammation. In this study, isolated liver granulomas were fractionated into macrophage or lymphocyte-eosinophil-rich populations to determine the cellular origin of these hormones. Immunoreactive angiotensins I, II, and III (AI, AII, and AIII) were detected in granuloma macrophage homogenates by radioimmunoassay and chromatography. No angiotensins were associated with the lymphocyte-eosinophil fraction. Isolated granuloma macrophages, but not the lymphocyte-eosinophil fraction, retained appreciable angiotensins when cultured in vitro and spontaneously released these peptides into the culture medium. Similarly, culture of these cells in the presence of exogenous angiotensinogen or AI resulted in additional AI and/or AII/III appearing in the medium. These data support the contention that granuloma macrophages generate angiotensins from both endogenous and exogenous substrates.

Eosinophilia VI, spontaneous synthesis of chemokinetics, chemotactic, complement receptor-inducing activities for eosinophils by bronchial t lymphocytes of asthmatic-bronchitic patients

T lymphocytes were separated from the bronchial mucus of five patients with extrinsic asthma and chronic and mild bronchitis and who had numerous eosinophils in the bronchial mucus but no significant blood eosinophilia. The bronchial lymphocytes spontaneously, that is without treatment with antigens or mitogens, released into serum-free synthetic medium one or more substances in the molecular weight range of 30 000 to 60 000 daltons. These substances when tested on eosinophils of normal persons stimulated random movement (chemokinesis), attracted them (chemotaxis), enhanced their chemotactic response to activated complement, and increased the expression of C4 and C3b receptors. Chemokinetic and chemotactic activity for neutrophils was weak. No eosinophil-stimulating activity was found in cultures of bronchial lymphocytes treated with puromycin to inhibit synthesis. The blood lymphocytes did not spontaneously synthesize the substance(s). It is not known if the several eosinophil-stimulating activities are due to one or more substance(s), but the nature of the eosinophil responses, molecular weight and other features, indicate similarities with the 'eosinophil stimulation promoter-chemotactic' factor reported to be released from mouse or human lymphocytes treated with antigen. Eosinophil stimulation resulting in increased expression of specific receptors, and potential for non-specific adherence, by trapping or arresting randomly migrating cells, is believed to mediate accumulation of cells in an affected organ. Prolonged synthesis of such products as from activated lymphocytes in the lung, could account for much of the local eosinophilia.