The role of cytokines in immunity and immunopathogenesis of pirolasmoses.

Cells involved in innate and adapted immunity produce cytokines capable of orchestrating the immune response to Babesia and Theileria infections. Thus, CD4-postive T cells recognise peptide fragments of the parasites in the context of the major histocompatibility complex (MHC) class II antigen and produce gamma interferon (IFN-gamma) to activate macrophages for enhanced phagocytosis and intracellular killing of the parasites. In addition, CD4-positive T cells produce interleukin 2 (IL-2) which is essential for the clonal expansion of CD8-positive T cells. The latter cells kill Theileria-infected host leucocytes in an MHC class I-dependent manner. On the other hand, the overproduction of proinflammatory cytokines contributes to disease progress.