A Study To Identify The Presence Of IL-10 And IFN-y In Leukocytes During Theileria Parva Infection In Cattle

Abstract

The gene expression of two immunoregulatory cytokines, IL-10 and IFN-y, during infection of bovine leukocytes with T. parva was investigated at the single cell level. Initial results obtained from in vitro studies with infected cells using RT -PCR showed that both IL-l 0 and IFN-y messages were present. The ability of Theileria-infected cells to produce IL-l 0 transcripts was a consistent feature. However, their ability to exhibit IFN-y messages was less consistent. On application of in situ hybridisation technique using bovine IL-IO and IFN-y-specific riboprobes, it was demonstrated that most infected lymphocytes produced IL-10 and that few of these cells displayed expression of IFN-y transcripts. Thus, judging from the relative abundance of IL-J 0 and lack of IFN-y mRNA, the expression of IL-IO, a cytokine known to inhibit IFN-y production and functions, was shown to be upregulated in leukocytes responding to T. parva infection in cattle. These experiments did not demonstrate the production of biologically active IL-10 during the infection. However, the accompanying relative absence of IFN-y mRNA in situ may suggests that biologically active IL-10 was produced and blocked the production of IFN-y, an important effector TH 1 cytokine. The apparent upregulated expression of IL-10 during infection with T. parva is indicati ve of a regulatory role for this cytokine in the mediation of susceptibility to acute disease. This parasite-instigated induction and upregulation of IL-l0 expression may represent an important strategy by which intracellular T. parva eludes IFN-y-depehdent cell-mediated immune destruction. Through its induction of tissue-damaging metalloproteinase, IL-I0 presence also offers a biochemical explanation to the possible mechanism of propagating the Iymphoproliferative, immunopathologic and tissue destructive phenomena observed in ECF.