Up-regulated expression of Interleukin-2 Receptor alpha in tick resistant cattle
Jones, M.E., Piper, E.K., Minchin, C.M., Zhang, B., Moolhuijzen, P.M., Gondro, C., Jonsson, N.N., Bellgard, M.I., Lew-Tabor, A.E. and Jackson, L.A. (2008) Up-regulated expression of Interleukin-2 Receptor alpha in tick resistant cattle. In: ComBio 2008, 21 - 25 September 2008, Canberra, A.C.T.
The cattle tick Rhipicephalus microplus is responsible for severe production losses to the cattle industry worldwide. Bos indicus cattle are naturally more resistant to R. microplus than B. taurus, however, the mechanism of this resistance is relatively unknown. Pre-exposed B. taurus and B. indicus cattle were artificially infested weekly with tick larvae for 6 weeks. B. indicus cattle carried significantly fewer ticks (P=0.000) than the B. taurus cattle. Peripheral blood samples were collected to examine gene expression (Affymetrix microarrays), to analyse markers on circulating leukocytes, and to prepare lymphocyte cell cultures. IL-2 is a T cell growth regulator and a central immune system regulator. IL-2R alpha delivers IL-2 to the signalling complex and acts as a regulator of signal transduction. B. indicus cattle demonstrated a significant increase in the percentage of cells positive for the IL-2R-alpha surface marker and significantly higher IL-2R-alpha gene expression in the peripheral blood, than did the B. taurus cattle. In vitro cell cultures from B. indicus cattle had significantly higher expression of IL-2R-alpha mRNA than B. taurus cells when stimulated with tick extract. To further study this gene, siRNAs targeting IL-2R-alpha were introduced into tick stimulated in vitro cultures and IL-2R-alpha expression was partially silenced in B. taurus lymphocytes but not in B. indicus. Identifying the immune pathways employed by tick resistant cattle is an essential step for the development of anti-tick vaccines that promote an appropriate immune response to infestation.
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|Murdoch Affiliation:||Centre for Comparative Genomics|
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