Antigen localization and the induction of resistance in XXXX vaccinated with irradiated cercariae of Schistosoma mansoni.

@entity19 @entity281 @entity536 @entity71075 @entity204
The fate of 75Se-labelled parasites and their released pre-synthesized macromolecules has been followed in three @entity19 @entity281 models. Parasite numbers in specific tissues were determined by autoradiography, and released material was estimated by gamma-counting of tissues, with adjustment for the presence of parasite-associated radiolabel. Marked differences were found between the three models. The pattern of migration of normal schistosomula was similar to that previously reported. In addition we have described the transit of parasites through the lymph nodes draining the @entity281 site. Significant quantities of released material were detected in the skin, draining lymph nodes, bloodstream and liver. The circulating material was of parasite origin, macromolecular, and hence potentially antigenic. In comparison to the normal @entity536 (inducing a high level of resistance to challenge) persisted in the skin, draining lymph nodes and lungs, releasing a proportionally greater amount of material in the nodes. In @entity19 exposed to attenuated parasites and treated with the compound @entity71075 at 24 h (inducing a low level of resistance) there was an early @entity204 and rapid clearance of the parasites whilst still in the skin. This situation resulted in the highest levels of released material in the skin, bloodstream and liver, but negligible levels in the draining lymph nodes. We suggest that the persistence of radiation-attenuated parasites in the skin and draining lymph nodes, together with the prolonged release of antigen in the latter site, compared to the normal situation, are major factors in the induction of resistance.
