Mice were infected once, twice or many times with Strongyloides ratti infective larvae, and the parasite was allowed to complete its development. Other mice were infected many times with either infective larvae only, by aborting the
infection with
cambendazole, or with adult worms transferred by intra-oesophageal intubation. Sera from these animals were analysed by immunoblotting against SDS-PAGE separations of larval and adult worm water-soluble,
deoxycholate-soluble,
sodium dodecyl sulphate-soluble and excretory/secretory
antigens. Minimal antibody responses were observed after primary and
secondary infections. Mice exposed to multiple complete
infections reacted strongly to both larval and adult
antigens but greater responses were observed against the larval preparations. Stage-specific effects were noted in mice infected with larvae only or adult worms only. Mice exposed only to larvae reacted with larval
antigens and to a minor degree to somatic adult worm
antigens while those mice which were exposed only to adult worms failed to react with any of the
antigen preparations. Some cross-reactions were found, however, as mice infected only with larvae displayed strong reactions against both larval and adult excretory/secretory products. These data demonstrate differences in sero-reactivity to infective larvae and adult worms and suggest that humoral immunity is induced by larvae migrating through the tissues and not by adult worms in the gut.