Schistosoma mansoni: modulation of schistosomular lipid composition by serum

Human serum and foetal calf serum have been compared in terms of their ability to modify the biochemical and immunological properties of the schistosomular surface. Artificially transformed schistosomula were incubated in the presence of serum for 24 h and then radioiodinated using the chloramine T method. With this method only lipids are labelled. Foetal calf serum produces a net loss of lipids from the schistosomula, particularly of mono- and diglycerides. Human serum however, promotes not only a loss of mono- and diglycerides, but also a substantial uptake of cholesterol and triglycerides. Schistosomula recovered from the lungs of mice could also be labelled and contained besides triglycerides, an increased amount of cholesterol esters. The modulation of surface lipids in worms cultured with human serum correlates with the observation that such schistosomula develop significantly greater protection against eosinophil-mediated cytotoxicity in vitro than do individuals incubated with foetal calf serum. On the other hand, schistosomula cultured in the presence of either human serum or foetal calf serum develop the same degree of protection against complement-dependent lethal antibody; this result indicates that resistance against complement-mediated damage may be independent of the uptake of cholesterol and/or triglycerides, and might involve only limited alterations in the surface configuration of the schistosomulum.