Immunological characteristics of natural resistance in Microtus fortis to infection with Schistosoma japonicum

Objective To explore the immunological characteristics of natural resistanc e to Schistosoma japonicum infection in Microtus fortis (MF) living in the Dongting Lake area. Methods Passive transfer of sera from uninfected laboratory bred MF (BMF) t o albinao mice (AM) was performed to observe the acquired protection. Sodiu m dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme- linked immunoblotting (ELIB) methods were used to recognize 4 different lif ecycle stage antigens of S. japonicum by sera from wild MF (WMF), BMF, BMFi 3 and BMFi9. Tests were also performed on in vitro killing effect of sera a nd/or lymphocytes from BMF and WMF to schistosomulae; quantitative determin ation of C-3 and C-4 by immunoturbidometry, and interleukin-4 (IL-4) and an tibodies to the 4 stage antigens in sera from WMF, BMF and infected BMF by ELISA. Results Compared with the control group, stool eggs per gram (EPG) of AM in the test group was significantly reduced by 81.54%, miracidium hatching ra te, by 50.67%, liver egg counts, by 72.07%, the diameter of hepatic egg gra nuloma, by 70.39 mu m. Western blotting probed with the 4 MF sera all revea led 7 specific bands for SSA, 3 for AWA and SEA, but none for CA antigens. The sera and/or lymphocytes from WMF and BMF gave obvious killing effects o n schistosomulae with an adjusted death rate of 64.12% - 78.83%. The levels of "natural antibodies" produced by MF to S. japonicum were in the followi ng order: anti-SSA > anti-AWA > anti-SEA > anti-CA, all of which increased significantly after the infection. Serum levels of C-3, C-4 and IL-4 in uni nfected BMF were significantly higher than those in AM. After infection, le vels of C-3 and C-4 were further increased respectively by 72.83% and 295.4 9% in the 4th week and IL-4 by 303.83% in the 9th day. Conclusions Immunological characteristics of innate resistance in M. fortis to S. japonicum infection were existed with no significant difference betw een WMF and BMF.