The in vitro Effect of Normal and Immune Serum upon the Cercariæ of Schistosoma mansoni

Abstract

The majority of normal sera proved in vitro to be cercaricidal to larvae of S. mansoni. Of 502 normal sera. 21 per cent, were noncercaricidal whereas the remainder exhibited varying degrees of cercaricidal potency.The cercaricidal factor was thermolabile and disappeared during storage. It bore several points of similarity to complement.The cercaricidal factor was present to a varying degree in sera from all species investigated. Apparently normal sera from all cattle and different proportions of other species, caused an enveloping precipitate to form around the cercariae. This bore no obvious relationship to the nematode worm burden or presence of F. hepatica.An enveloping precipitate formed around cercariae of S. mansoni when placed in vitro in immune sera and incubated at 87°C. This occurred in serum immune to S. haematobium as well as to S. mansoni. It is not known-whether age and weight of infection influence the rate and extent of envelope precipitation.