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

Mice immunized with a glucan-killed parasite vaccine exhibited enhanced resistance to Leishmania donovani infection as evidenced by decreased hepatic parasite burdens when compared to unvaccinated controls. This resistance was not seen in mice immunized with killed parasites alone. Glucan vaccination resulted in increased resistance at day 6, but this effect was no longer present by day 20 of the experiment. Treatment of vaccinated and control mice with antithymocyte sera abrogated protection against infection, whether such resistance was vaccine induced or the result of acquired immunity.