Effect of cyclosporin A on the proliferation of bovine lymphocytes to concanavalin A and on the growth of Theileria annulata-infected bovine cells.

After being inoculated by Hyalomma ticks, the sporozoites of Theileria annulata invade bovine lymphocytes, where they subsequently differentiate to schizonts. The infected cells are induced to a continuous proliferation which can be enhanced by human recombinant interleukin 2 (hrIL-2). In the present study, we examined the influence of cyclosporin A (CsA) on the growth of schizont-containing cells and compared with its effect on bovine peripheral blood lymphocytes (PBL) responding to Concanavalin A (ConA). In both cell types, the proliferation was inhibited in a dose dependent manner, which was not restorable in T. annulata-infected cells even after addition of hrIL-2. In contrast, ConA-blasts were able to undergo a proliferative response provided they were treated with high doses of CsA. Both, T. annulata-infected cells and bovine ConA-blasts express IL-2 receptors (IL-2R). The binding of radiolabelled hrIL-2 to ConA-blasts and T. annulata-infected cells was only partially inhibited after treatment with CsA. CsA was not toxic for the parasites, since the treated cells still contained schizonts which did not show any morphological abnormality.