The effect of transferred immune serum and IgG on the response of recipient mice to concurrent infections with larvae has been investigated. Following one infection, recipient mice harboured fewer worms than control mice, the worms were stunted and thier fecundities were greatly reduced. Four concurrent infections was found to reduce worm burden and worm fecundity, and induce an increase of serum antibody titers in no-treatment and normal serum given mice. On the other hand the transferred immune serum and IgG appeared to adversely affect the protective immune response in recipient mice. In recipient mice, worm fecundity was consistently increased throughout experiment and harboured more worms after four infections than control mice. Serum anti-N. dubius antibody titers of mice made passively immune by transfer of immune serum and IgG were not significant difference between one infection and four infections. Thus, transferred immune serum and IgG may debilitate host antibody production.
