title: Immunological characteristics of natural resistance in Microtus fortis to infection with Schistosoma japonicum.
abstract: OBJECTIVE
  To explore the immunological characteristics of natural resistance 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) to albinao mice (AM) was performed to observe the acquired protection. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunoblotting (ELIB) methods were used to recognize 4 different life-cycle stage antigens of S. japonicum by sera from wild MF (WMF), BMF, BMF13 and BMF19. Tests were also performed on in vitro killing effect of sera and/or lymphocytes from BMF and WMF to schistosomulae; quantitative determination of C3 and C4 by immunoturbidometry, and interleukin-4 (IL-4) and antibodies 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 rate, by 50.67%, liver egg counts, by 72.07%, the diameter of hepatic egg granuloma, by 70.39 microns. Western blotting probed with the 4 MF sera all revealed 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 on 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 following order: anti-SSA > anti-AWA > anti-SEA > anti-CA, all of which increased significantly after the infection. Serum levels of C3, C4 and IL-4 in uninfected BMF were significantly higher than those in AM. After infection, levels of C3 and C4 were further increased respectively by 72.83% and 295.49% 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 between WMF and BMF.
authors.affiliation: Hunan Institute of Parasitic Diseases, Hunan 414000, China.
authors.forename: Y
authors.initials: Y
authors.lastname: He
authors.forename: X
authors.initials: X
authors.lastname: Luo
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: X
authors.initials: X
authors.lastname: Yu
authors.forename: J
authors.initials: J
authors.lastname: Lin
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: S
authors.initials: S
authors.lastname: Liu
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000276:immunology*; D007113:Immunity, Innate; D007116:Immunization, Passive; D051379:Mice; D011817:Rabbits; D011897:Random Allocation; D012549:Schistosoma japonicum / Q000472:pathogenicity*; D012554:Schistosomiasis japonica / Q000276:immunology*; D013045:Species Specificity