Immune responses to oral infection with Echinococcus multilocularis protoscoleces in gerbils: modified lymphocyte responses due to the parasite antigen.

Immune responses to oral infection with Echinococcus multilocularis protoscoleces in Mongolian gerbils were investigated. Gerbils not treated with prednisolone expelled most of the parasites within 3 days post-infection and induced parasite-specific intestinal IgA secretion after the oral inoculation with protoscoleces. In contrast, prednisolone-treated gerbils harbored notable numbers of parasites, and the parasite-specific intestinal IgA secretion was lower. In gerbils not treated and orally inoculated with protoscoleces (infected group), parasite-specific antibody levels in sera and intestinal washings were elevated, but blastogenesis against protoscolex antigens was observed only in cells from Peyer's patches at 14 days post-infection. Concanavalin A-induced proliferative lymphocytes from both infected and naive gerbils were suppressed by adding protoscolex somatic antigen. These data indicate that while parasite-specific antibody responses were observed, lymphocyte proliferative responses were suppressed by parasite infection/antigens in the Mongolian gerbil, prednisolone-untreated rodent definitive host model.