Recognition of microbial pathogens by the innate immune system is essential to development of an adaptive immune response and is dependent on signaling by Toll-like receptors (TLR). TLR are Pattern Recognition receptors (PRR) that recognize and respond rapidly to invading bacteria leading to the production of pro-inflammatory cytokines, radical oxygen species, nitric oxide and the induction of adaptive immunity. In parallel to this microbes have co-evolved mechanisms to avoid host responses, and may even exploit TLR induced innate responses to their own advantage. Elucidation of the mechanisms of pathogen recognition and host immune evasion by the TLR pathways is central to our understanding of how these factors contribute to pathogenesis in the susceptible host and for developing improved approaches to control, treatment and immunoprophylaxis of this important disease.

In this study we have analysed the expression of eight ovine TLR genes in peripheral blood and several intestinal sites by comparative qPCR to determine if the levels of TLR expression is modulated in these tissues by disease. We have found significant changes in the expression of several TLRs at various sites. Additionally there appears to be a substantial difference in gene expression between lesion grades for some genes. The implications for diagnosis and pathogenesis of disease will be discussed.