Serial observations of circulating immune complexes in patients with acute schistosomiasis.

To define further the role of circulating immune complexes in acute schistosomiasis, serial determinations of [125I]Clq binding activity (ClqBA) in 15 patients with this disease were made before and after treatment with niridazole. Levels of ClqBA were elevated in 13 of these patients and in general rose early in the course of disease, reaching maximal levels by 10 weeks after exposure; the levels were correlated with disease severity (r = 0.70, P less than 0.01) and with the concentration of Schistosoma mansoni eggs in the stool (r = 0.59, P less than 0.05). The rise and fall in levels of ClqBA was associated in most instances with the temporal course of other laboratory values reflecting disease activity. The close association of circulating immune complexes with measures of disease activity suggests that these complexes are important in the pathogenesis of acute schistosomiasis.

Factors in the pathogenesis of acute schistosomiasis mansoni.

Acute schistosomiasis mansoni was studied in 26 Puerto Rican patients whose clinical presentations differed widely in severity. Severity of illness was found to be positively correlated (r = 0.79) with the intensity of infection as measured by the concentration of eggs of Schistosoma mansoni in stool specimens. However, some patients had severe illness but relatively light infections. The disappearnace of symptoms and return toward normal of laboratory measures of disease activity were not associated with any diminution in the fecal egg count. Elevations of IgG, IgM, IgE, and of titers of anibody in serum indicated that the illness is associated with intense immune activity. The magnitude of the IgG and IgE responses was related to intensity of infection. The fact that incubation periods were shorter than the time needed for schistosomes to reach adulthood and lay eggs suggests that the syndrome can be initiated by parasite stages present before oviposition. No marked changes in complement (C3, C3p, C4, and CH50) and no signs of renal disease were noted in any of these patients.

The acquisition and loss of antigen-specific cellular immune responsiveness in acute and chronic schistosomiasis in man.

To characterize the development and evolution of cellular immune responsiveness in individuals infected with the parasite Schistosoma mansoni, we studied fifteen patients with acute, subacute and chronic schistosomiasis. Lymphocytes from the three acutely infected patients responded vigorously to schistosome antigens in an in vitro blastogenic assay. By contrast, cells from nine chronically infected individuals were essentially unreactive to these same antigens. Patients infected for an intermediate period of time (9 months) generated responses between those of acute and chronic patients. The diminished responsiveness of chronically infected individuals was specific for schistosome antigens and did not extend to humoral immune responses. Following treatment of the infection with niridazole, these patients temporarily regained responsiveness to schistosome antigens. From these data we speculate that during the course of this parasitic helminth infection there develops a progressive and specific modulation of antigen recognition and proliferation by lymphocytes to schistosome antigens, and that such diminished immune reactivity may be important in maintaining the unique biological relationship which exists between a host and its parasites.