Eosinophil-dependent cytotoxicity in rat schistosomiasis. Involvement of IgG2a antibody and role of mast cells

Using Schistoma mansoni schistosomula collected in vitro and sensitized with 42-day-infected rat serum, normal rat peritoneal cells enriched in eosinophils were proven to subsequently adhere to and kill the schistosomula within 24 to 48 h. The cell-dependent, heat-stable antibody in infected rat serum reached a peak between 30 and 42 days after infection. Inhibition experiments with aggregated immunoglobulins indicated the role of IgG2a antibody in the adherence of eosinophils to sensitized schistosomula. The immune absorption technique showed that IgG2a antibody was involved in the mechanism of cytotoxicity of effector to target cells, whereas the role of IgE antibody could be excluded. Ultrastructural studies revealed the constant presence of eosinophils and mast cells in contact with schistosomula. The use of purified cell populations showed that the cytotoxic effect of the original cell population was significantly decreased after depletion of mast cells and partially restored after addition of mast cells. These observations, together with those concerning the role of IgE immune complexes in macrophage cytotoxicity, suggest the possible participation of anaphylactic antibodies in immunity to schistosomes in the rat.

Treatment of hepatic hydatid disease with mebedazole: preliminary results in four cases

Mebendazole was given to four patients with hepatic hydatid disease. In three patients hydatidosis had remained after surgery, and in the fourth it could not be treated surgically. Mebendazole was given orally in maximum doses of 400-600 mg three times a day during courses lasting 21 to 30 days. Ultrasonic echotomography showed a complete regression of the intrahepatic cysts after four to 13 months in all four cases. In three patients the course of treatment had to be repeated. Mebendazole also induced clinical improvement and a progressive lowering of the concentration of specific IgE of Echinococcus granulosus. During treatment circulating blood levels of specific immune complexes of antigen 5 were increased. These observations indicate that mebendazole has a lethal effect on E granulosus cysts in primary hydatid disease in man and that the efficacy of chemotherapy can be assessed with ultrasonography and by measuring changes in the concentration of specific IgE of E granulosus and circulating immune complexes.

Immunological studies in human schistosomiasis. III. Immunoglobulin levels, antibodies, and delayed hypersensitivity

Levels of IgG, IgE, IgM, and IgA were determined, specific antibodies were detected by the fluorescent antibody test, hemagglutination test, complement fixation test and immunoelectrophoresis, and intradermal tests for delayed hypersensitivity to Schistosoma mansoni antigens were performed in Brazilian patients with schistosomiasis mansoni. The results were compared according to the clinical forms of the disease. IgG levels and antibody titers increased progressively in the subclinical, hepatomegalic, and hepatosplenic forms and there was a statistical relationship between IgG levels and the intensity of responses to the four serological tests; Delayed hypersensitivity (DHS) was found more frequently in hepatosplenic patients and more particularly in those with splenomegaly. DHS also correlated with age, but not with sex or with skin color. The strongest DHS reactions were observed in patients 20 to 34 years old, and in those having the highest fecal egg output. IgG levels, antibody titers, and DHS responses decreased after splenectomy and portal filtration of the worms. No significant variation was observed between untreated subjects, patients who were splenectomized and a group not subject to reinfection for 4 yearsk0

Interaction between IgE complexes and macrophages in the rat: a new mechanism of macrophage activation

In earlier studies we found that normal rat macrophages, preincubated at 37 degrees C with the serum of syngeneic rats immune to Schistosoma mansoni, strongly adhered to S. mansoni schistosomules whereas no significant adherence was induced with serum from normal rat. Using 51 chromium release assay, it now proved that immune serum-incubated macrophages lysed the schistosomules in 18 h. Absorption experiments and ultracentrifugation of the immune serum showed that immune complexes containing specific IgE antibody against S. mansoni and soluble parasite antigens induced macrophage adherence and cytotoxicity. Using various labeling techniques, the binding of aggregated rat IgE to the macrophage surface at 37 degrees C is evident in conditions where endocytosis is neglible. The binding of immune complexes containing IgE antibody to S. mansoni elicits dramatic ultrastructural changes in the macrophage and an increase of its lysosomal enzymes together with specific lytic activity for the schistosomules. The parallel development of immune serum-induced macrophage adherence or cytotoxicity with the level of circulating IgE antibody to the parasite in correlation with the development of immunity in the rat, suggests that this new mechanism of macrophage activation could play a role in immune effector mechanisms against S. mansoni. Therefore, IgE acts as a humoral mediator of cellular immunity.

Drugs as ligands of immunogenic molecules in parasites: an approach to the isolation of target-antigens

Schistosomicide drugs are used as ligands to isolate the target antigens of schistosome by affinity chromatography. Anti-target antigens immune sera produced in rabbit permit their localization on the parasite using immunofluorescence. Target antigens of some drugs determine a relatively high immunoprotection in rat or mouse schistosomiasis infection.

Immunological studies in human schistosomiasis. II. Antibodies cytotoxic for Schistosoma mansoni schistosomules

Complement dependent cytotoxic antibodies for Schistosoma mansoni schistosomules were studied in a Brazilian population. The sera of S. mansoni-infected patients gave a high percentage of cytotoxicity (63.4%) compared with sera from persons not infected (8.7%). The IgG class and the specificity of these cytotoxic antibodies are defined. The index of lethality appeared to be independent of the titers of other specific anti-S. mansoni antibodies. A statistical correlation was found between the index of lethality and both the severity of the disease and delayed hypersensitivity to S. mansoni antigen. The significance of cytotoxic antibodies in human schistosomiasis and their relevance to immunity in man are discussed.

[The role of specific IgE antibodies in the immune adherence of normal macrophages to schistosomes of Schistosoma mansoni]

Specific IgE antibodies from immune rat serum were demonstrated to mediate the immune adherence of normal rat macrophages to Schistosome mansoni schistosomules, which was followed by a cytototoc action. Hence, a new positive role of IgE antibodies in protective immunity is argued.