Antithymocyte serum suppression of immunity in mice immunized to Leishmania donovani.

M ice im m unized w ith a g lucan-k illed parasite vaccine ex h ib ited enhanced resistance to Leishmania donovani infection as evidenced by decreased hepatic parasite burdens when compared to unvaccinated con­ trols. This resistance was not seen in mice immunized with killed parasites alone. Glucan vaccination resulted in increased resistance at day 6, bu t this effect was no longer present by day 20 of the experiment. Treatment of vaccinated and control mice with antithymocyte sera abrogated protec­ tion against infection, w hether such resistance was vaccine induced or the result of acquired immunity.