Modulation of cell-mediated immunity in mice with chronic unisexual or bisexual Schistosoma mansoni cercarial infection.

Three groups of C57BL/6J female mice were infected with female Schistosoma mansoni cercariae alone, male cercariae alone, or both sexes of cercariae. In a longitudinal study, the spleen cell proliferative responses to the mitogens phytohaemagglutinin (PHA) and Escherichia coli lipopolysaccharide (LPS) were monitored. Significant immune suppression was found in the three infected groups when compared with uninfected controls. Within the infected groups, mice inoculated with both sexes of cercariae were significantly more suppressed than those with single-sex cercarial infection. Thus, in addition to schistosome eggs, either sex of S. mansoni worms is capable, although to a lesser extent, of inducing hyporesponsiveness of cell-mediated immunity (CMI) in chronic schistosomiasis mansoni.