Quantification, dynamics, and mechanisms of pulmonary inflammatory response around schistosomula of Schistosoma mansoni.

The inflammatory response around schistosomula injected into the lungs of uninfected mice and mice infected with Schistosoma mansoni was quantified. In uninfected mice, the inflammatory response started at 1 hour and peaked at 6 days, whereas in the infected mice, the inflammatory response was accelerated and peaked at 24 hours. This latter inflammatory reaction was 1.5 times greater than the 6-day reaction found in uninfected controls. Neutrophils and mononuclear cells were seen around schistosomula impacted into the pulmonary microvasculature by 1 hour; later, however, eosinophils constituted the predominant cell. This augmented inflammatory response was detected in mice infected with S mansoni first at 4 weeks after injection and peaked at 12 weeks. The augmented response correlated with acquired resistance as assayed by the recovery of the organisms from the lungs 4 days after challenge. Augmented inflammatory reaction and increased protection was induced by subcutaneous sensitization with dead schistosomula or eggs but not by cercariae or adult worms. Adoptive transfer of serum but not lymphoid cells from 12-15 week-infected mice resulted in augmented inflammation and enhanced resistance in recipient normal animals. The serum activity was absorbed by both schistosomula and eggs and was shown to reside in the fraction containing IgG1.