Characterization of protective T cells in the acquired response to Leishmania donovani in genetically determined cure (H-2b) and noncure (H-2d) mouse strains.

The response to reinfection with Ethiopian Leishmania donovani was evaluated in genetically determined noncure (H-2d) B10.D2 mice that are able to resolve infection due to sublethal irradiation pretreatment after inoculation with a low parasite dose and in C57BL/10 mice that demonstrate the genetically determined cure (H-2b) response to L. donovani. It was found that after resolution of primary infection, C57BL/10 (cure) mice and sublethally irradiated B10.D2 (noncure) mice were resistant to rechallenge with L. donovani. Noncure mice inoculated with a low dose of amastigotes were not, however, solidly immune to reinfection. Adoptive-cell transfer experiments were then done to determine the T-cell subset that was associated with resistance to reinfection, and thus the development of immunity, in sublethally irradiated B10.D2 noncure mice and in C57BL/10 cure mice. T-cell-enriched preparations from spleens of immune donors were treated with subset-specific antibodies and complement prior to adoptive transfer in unprimed recipients. The results of the adoptive transfer experiments provide evidence that the genetically determined cure (H-2b) response in C57BL/10 mice and the cure response in genetically determined noncure (H-2d) B10.D2 mice brought about by sublethal irradiation pretreatment are mediated primarily by an L3T4+ Lyt-2- T cell.