Toll-like receptors (TLRs) fonn a vital part of the innate immune response to infection through the recognition of diverse molecular patterns leading to the generation of an inflammatory reaction. The resulting cytokines act on both tissue and immune cells to coordinate the response to infection. Cytokine networks also play an important role in the modulation of an increasing number of diseases which we now understand to have an inflammatory basis. TLR activation has been implicated in both chronic and acute diseases, and understanding and modulation of these responses may be central to th'e manageinent of inflammatory disease. This thesis investigates the impact of an enigmatic early response cytokine macrophage migration inhibitory factor on the TLR response of human cells. I have shown that the role ofMIF as an inflammatory cytokine is not clear-cut. Recombinant MIF failed to induce a significant inflammatory response from either a monocytic THP-l cell line or primary human monocytes. Furthennore, it failed to modulate the dexamethasone induced suppression of TLR induced cytokine release, a classically described activity of MIF. In keeping with these observations, anti-MIF antibodies did not modulate the LPS induced cytokine release of monocytes or monocytelHUVEC cocultures, which suggests that MIF may not act as a classical autocrine cytokine. I have demonstrated using a specific, cell-penneable MIF antagonist, known as ISO-I, and MIF siRNA, that MIF modulated specific arms of the TLR response leading to the activation of mitogen activated protein kinases (MAPKs) in monocytic cells. Cell-type spe~ific downstream effects on cytokine production were also seen. ISO-l potentiated LPS induced p38 phosphorylation and TNFa release from THP-I cells. Conversely, in primary monocytes, TNFa and CXCL8 production in response to LPS was significantly inhibited by both ISO-I and MIF siRNA, whilst TNFa but not CXCL8 production was maintained in response to TLR2 activation. LPS induced cytokine release from MDMs was unaffected by :NIIF inhibition. During the course of this thesis I have also observed differences in TLR2 induced inflammatory reactions in primary monocytes. This observation was explored further. These data suggest that whilst targeting MIF may be a useful therapeutic axis in disease, the roles of MIF are not straightforward. Further work will be needed to fully address the roles of this molecule in human biology.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:505343 |
| Date | January 2009 |
| Creators | West, Peter William |
| Publisher | University of Sheffield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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