Maturation in vivo of Schistosoma mansoni schistosomula after culture in vitro with granulocytes and antibody.

Seven experiments were carried out to test the relationship between the morphological assay for damage to schistosomula in vitro with toluidine blue and the loss of the ability of damaged organisms to mature in vivo. Schistosomula were prepared by penetration of rat skin and cultured for 12 to 38 h in the presence of various combinations of purified human eosinophils or neutrophils and heat-inactivated human antischistosomular serum. Samples were scored for microscopically detectable damage, and the remaining organisms were injected intravenously into normal mice. These mice were perfused after 5.5 to 7 weeks, and the recovery of adult worms was determined. After culture of schistosomula in medium alone, between 8.4 and 32.7% of injected organisms matured into adult worms. There was no significant difference in the capacity of freshly prepared and cultured schistosomula to mature in vivo. Schistosomula cultured with antibody alone showed no significant damage in vitro, and in only one of seven experiments was there a significant (35%) reduction compared with the medium controls in their capacity to mature in vivo. Schistosomula cultured with neutrophils alone or eosinophils alone showed no significant damage in vitro and no loss of viability in vivo. Schistosomula cultured with neutrophils and antibody showed a 28% reduction in recovery in one experiment but an increase in recovery (12 and 46%) in two other experiments. In contrast, schistosomula cultured with eosinophils and antibody showed evidence of both marked damage in vitro (22 to 93% dead organisms) and loss of viability in vivo (26 to 98% reduction in recovery) in all seven experiments. These findings justify the use of the toluidine blue morphological assay as an estimate of irreversible damage to schistosomula and confirm that human eosinophils and neutrophils differ markedly in their capacity to mediate antibody-dependent damage in vitro.