Dr. Murai Éva szerk.: Parasitologia Hungarica 20. (Budapest, 1987)

A strong challenge of the convalescent voles is also suitable for demonstrating this temporary immunity (Table 1). Namely, in voles that had convalesced 2 weeks earlier (at the peak of immunity) splenomegaly fails to recur, and by day 5 after challenge the trypanosomes disappear from their blood. On the other hand, in voles that had recovered from infection 3 months earlier, challenge again causes moderate splenomegaly, and trypanosomes are occasionally demonstrable in their blood on day 5 after challenge. Death of three mice per group on PI days Treatment of mouse _ groups 1 2 3 4 5 6 7 8 9 10 11 12 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 Controls (without serum) Controls + normal vole blood plasma Convalescent vole plasma obtained on day 5 7 9 21 •u 50 92 . A 50 92 X 50 92 Xmice simultaneously receiving vole plasma survived, however, after challenge these mice died as well as the control (susceptible) albino mice Fig. 6. Protection experiments in mice using blood of voles convalescing from Trypanosoma equiperdum infection. The mice were inoculated with 0, 5 ml vole plasma dilution ip. + 6x10^ trypanosomes sc. simultaneously DISCUSSION The present experiments have revealed that voles have a firm resistance to T. equiperdum infection. Large numbers of parenterally administered trypanosomes are eliminated from their blood within a few weeks. Trypanosomes are no longer demonstrable by experimental inoculation of mice in the blood and organs of voles killed one month after infection. At the same time, T. equiperdum antibodies appear in the serum already on PI days 5-7 and persist there for 2. 5-3 months. Thus, the vole belongs to the group of resistant rodents in which the inoculated trypanosomes cannot survive for long periods. The elimination of trypanosomes from the infected voles (i. e. cessation of the antigenic stimulus) is followed by the disappearance of trypanosomal antibodies 3 months after infection. The most probable explanation for this is the pronounced macrophage activation (considerable splenomegaly) developing to T. equiperdum and, possibly, to other Trypanosoma spp. as well. Therefore,