The effects of a soluble factor released by sensitized mononuclear cells incubated with S. haematobium ova on eosinophil migration.

Incubation of sensitized mononuclear cells from patients with schistosomiasis with specific antigen containing a suspension of viable Schistosoma haematobium ova resulted in the release of a soluble factor which was chemotactic for eosinophils. Production of this substance was detectable at 24 h and demonstrated peak chemotactic activity after 2 days in culture. The chemotactic potential was dose-dependent and attracted eosinophils obtained from patients with schistosomiasis or allergic diathesis. Human neutrophil motility was unaffected by this chemoattractant. Preliminary studies demonstrated that the chemotactic factor is a heat-stable substance with peak activity associated with a molecular weight of approximately 42,000. These findings may reflect an in vitro correlate of cell-mediated immunity and may indicate a role played by the lymphocyte in the control of eosinophil function in human biology.