| dc.description.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
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