ELEVATED AGGLUTINATION TITERS IN PLASMA OF BIOMPHALARIA-GLABRATA EXPOSED TO ECHINOSTOMA-PARAENSEI - CHARACTERIZATION AND FUNCTIONAL RELEVANCE OF A TREMATODE-INDUCED RESPONSE

Production of elevated haemolymph agglutination titres by Biomphalaria glabrata following exposure to Echinostoma paraensei miracidia was in vestigated, to characterize this parasite-induced response and to unde rstand its functional relevance. Both the dose of infection (1, 10 or 100 miracidia per snail) or the number of separate exposures to infect ion (between one and three, over a 4 or 8 day interval) were varied, a nd assuming a threshold dosage (10 miracidia per snail or higher) was exceeded, titres of juvenile snails peaked at 8-16 times the values fo r unexposed control snails, regardless of the exposure regimen. Adult snails, which are relatively refractory to infection, have slightly hi gher resting titres than juveniles, but exhibit only a 2- to 4-fold in crease in titre following exposure. Juveniles exposed to infection but lacking demonstrable infection had lower titres than snails with conf irmed infections. Exposure to infection increased heterogeneity of pla sma agglutinins and provoked production of unique specificities not fo und in unexposed snails. However, the overall pattern of agglutination responses for snails with successfully developed parasites did not di ffer from those in which parasite development was unsuccessful. Agglut inating activity was inhibitable by several different monosaccharides, although plasma from infected snails was relatively unaffected by nr- acetyl-glucosamine or N-acetyl-galactosamine. Wounding of snails provo ked no change in plasma agglutination activity. As the highest aggluti nation titres were produced in snails with successfully developing par asites and agglutinin composition did not differ between snails with s uccessful or unsuccessful parasites, the functional relevance of the r esponse remains enigmatic. The production of unique agglutinins follow ing exposure deserves additional study.